In this study, indentation tests of graphene-based polymer nanocomposites were carried out to determine the local elastic mechanical properties. The samples consist of epoxy matrix with graphene additives. Additives were added at levels of 0% as a control, 0.5%, 1%, 2.5%, 5% and 10% by weight. The local elastic properties such as moduli and hardness were calculated. After each indentation, the prints were characterized using scanning electron microscopy (SEM). It seems that the local mechanical properties of nanocomposite samples were improved as the amount of nano-additives increased. Based on the curve displacement and surface imaging, we can conclude that the nano-additives influenced the overall plastic mechanical behavior of the samples. For simulating micro-indentation test, a finite element analysis model was developed using ABAQUS software and compared to experimental tests. Good correlation was observed. To enhance the mechanical performance of monolithic epoxy, many researchers have used nanofillers such as graphene, carbon black, carbone nanotubes, and other carbonaceous materials to reinforce it, due to their high modulus of elasticity and capacity to stop crack propagation ,2,3. IndIndentation has been intensively used to characterize local mechanical properties of different materials such as polymer, composites, etc. The aim of this study was to quantitatively understand the effects of neat epoxy and NGP/epoxy on its indentation measurement with experimental and numerical approaches. Micro-indentation tests of graphene-based polymer nanocomposites were carried out to determine the local elastic mechanical properties. The samples consisted of epoxy matrix with graphene additives. Additives were added at levels of 0% as a control, 0.5%, 1%, 2.5%, 5% and 10% by weight. Our results clearly demonstrate that the influence of the presence of NGP in epoxy matrix on its indentation measurement can be significant.The nanocomposite samples were produced using the conventional dry mixing method and adding 0.5, 1, 2.5, 5 and 10 wt % of graphene to epoxy. To maintain uniformity and produce sound samples, the unfilled polymer and the composites were processed under identical conditions. Graphene used in this study was produced by exfoliation and reduction of graphite in our own laboratory . The polGraphene tends to agglomerate in chunks because of its small particle size, large surface area and superior particle activity. To improve the dispersion of graphene in epoxy resin, the graphene bundles were dry-blended in a blender to obtain a uniform density graphene. It was then weighed to obtain five concentrations ranging from 0 to 10 wt % with the epoxy resin system. The lowest graphene concentration selected was 0.5 wt %, an intermediate value of 5 wt %, and the maximum concentration used was 10 wt %. It was found that, for concentrations higher than 10 wt %, the mixing process became challenging and a well dispersed compound was very difficult to obtain.The nanofiller was added, based on the desired filler concentration, to the epoxy resin, which was previously mixed with the curing agent in a plastic container by hand for 5 min in a weight ratio of 100/26.4 (epoxy/curing agent). This blend was subsequently loaded in a three-roll mill mixer to obtain a homogeneous dispersion of graphene in the epoxy. The procedure was the same for all compositions, with the exception of 10 wt % of graphene. As the amount of nanofiller increased, the viscosity of the compound increased. Therefore, the 10 wt % compound was prepared in several steps. Here, a small amount of graphene was added to the resin, then it was mixed in the three-roll mill until the viscosity of the compound was reduced. Subsequently, more graphene was added. This step was repeated until all the graphene was incorporated in the resin. A three-roll mixing mill, from Lehmann Mills a, was emThe mixing of the compound was started by slowly pouring the pre-mixed compound  between feed and center rolls. The mixture then automatically passed between center and apron rolls by sticking to them, and a knife edge blade scraped the processed material off the apron roll and stored in the pan . When thAfterwards, both sides of the composite plates were polished by hand for 1.5 min each with a 180 grit emery paper, and then they were washed in water and dried.The mechanical properties of each constituent are listed in The mechanical properties of epoxy matrix with grapheme additives specimens were evaluated for each volume fraction using the indentation test. A CSM Micro-Hardness Tester  using ViFor this type of material, and to control the dispersion of graphene in the matrix, micro-indentation tests were carried out in the specimen . MinimumThe mechanical and physical properties of nanocomposites depend on the dispersion of filler agent into the matrix. Here, the dispersion of graphene in epoxy was analyzed using optical and scanning electron microscopes. The optical microscope specimens were produced by mounting a 5 mm × 5 mm × 5 mm composite cube in epoxy holder and polishing its surface to optical flatness through several steps. The SEM samples were obtained by breaking a thin strip of the composite in tension. The graphene layers in epoxy can be identified via color contrast caused by the polarized light. This method is qualitative because the color contrast often varies from one laboratory to another . HoweverFirst step: Vickers indenter approaches the surface.Second step: Loading phase up to the maximum load. The maximum load applied was 1000 mN.Third step: Holding the load. It was done to avoid the creep effect on the unloading characteristics.Fourth step: Unloading phase.The mechanical properties of epoxy matrix with graphene additives specimens were evaluated for each weight fraction using an indentation test. In this study, a CSM Micro-Hardness Tester with a Vickers diamond indenter was used. A minimum of eight indentation tests were carried out for every sample. Minimum distances of 0.5 mm between indentation marks were used to avoid any hardening effect from previous tests. For all the micro-indentation tests carried out, the maximum effort was set 1000 mN. The micro-indentation parameters used for the tests are: approach speed of 50 μm/min, contact load of 10 mN, load rate of 2000 mN/min, unload rate of 2000 mN/min, maximum load of 1000 mN and 20 s of pause. The elastic moduli, indentation depth, stiffness and hardness were determined as an average value of all specimen tests. For a rigorous approach and a realistic comparison, the testing conditions were the same for all specimens. Micro-indentation tests were performed using Vickers indenter, which monitors and records the load vs. displacement of the indenter. this the total depth under a load, Pt;ehis the elastic rebound depth during unloading;fhis the residual impression depth;ahis the surface displacement at the perimeter; andphis the contact indentation depth.The indentation depths:S, is defined as the slope at the beginning of the unloading curve.The contact stiffness, For a qualitative and quantitative study, it is necessary to ensure test reproducibility. The load–displacement curves for each graphene-based nanocomposite are shown in Pmax.As shown in 2, which increases to 28.90 (8.83%), 31.59 (19%), 33.37 (26%), 35.02 (32%) and 39.89 (50%) with the addition of 0.5 1, 2.5, 5 and 10 wt % NGP, respectively. This increment in hardness is due to a good dispersion and interfacial bonding between NGP and the epoxy matrix.E, δ, S and H) are listed in The load–displacement curves for the neat epoxy resin and various NGP/epoxy-based nanocomposites were analyzed. These curves were obtained by micro-indentation testing under a maximal load of 1000 mN. As a result, adding the graphene nanoparticles (NGP) to neat epoxy, the mechanical properties were altered. Indeed, the elastic modulus and the stiffness (slope for the unloading) were improved. The elastic modulus of the epoxy increased from approximately 2.7 GPa to 3.6 GPa upon the addition of 10 wt % of NGP to the epoxy resin. Our results also showed that the stiffness and hardness of NGP/epoxy samples increased by 42% and 40%, respectively. The values of mechanical properties  . A homogThe total mesh of indentation geometry was composed of 45,310 linear hexahedral elements of C3D8R for specimen, 4986 linear quadrilateral elements of R3D4 and 2 linear triangular elements of R3D3 for rigid indenter. We developed a numerical model of micro-indentation of the composites based on the implicit scheme using Abaqus FEA software. The force at each increment time was examined and correlated to the experimental variations to validate our numerical model and enhance the convergence of results. The boundary condition applied to the indenter is the displacement resulting from the experimental results . The corE), Stiffness (S) and hardness (H). Micro-indentation tools have provided a new method to evaluate the degree of dispersion of nano-additives and the local mechanical properties at the micrometric scale. The local mechanical properties can be considered representative of those of the bulk. This study shows that the indentation test could be an excellent technique in characterizing the mechanical properties of composites laminate reinforced with graphene nano-additives. It seems that the local mechanical properties of nanocomposite samples were improved as the amount of nano-additives increased. Based on the curve displacement and surface imaging, the influence of nano-additives on the overall plastic mechanical behavior is noticeable. A proper numerical model was developed for validating the experimental results. A small difference between two approaches was remarked and defined by the projected contact area and the graphene nano-additive distribution. It seems that graphene tends to improve the fracture toughness of composite and interfacial resistance.Local mechanical properties of an epoxy matrix reinforced with graphene nanoparticles (NGP) were investigated using depth-sensing micro-indentation. The addition of low percentage weight of NGP was considered as part of a strategy to enhance the mechanical properties of the nanocomposites. The graphene additives were uniformly distributed into the epoxy matrix, forming a nanocomposite. The study focused on the effect of the concentration of NGPs on the mechanical performance. It was found that the addition of NGP to epoxy matrix reduces the indentation depth (δ) and increases the Young modulus (


The incoming 5G technology requires antennas with a greater capacity, wider wireless spectrum utilisation, high gain, and steer-ability. This is due to the cramped spectrum utilisation in the previous generation. As a matter of fact, conventional antennas are unable to serve the new frequency due to the limitations in fabrication and installation mainly for smaller sizes. The use of graphene material promises antennas with smaller sizes and thinner dimensions, yet capable of emitting higher frequencies. Hence, graphene antennas were studied at a frequency of 15 GHz in both single and array elements. The high-frequency antenna contributed to a large bandwidth and was excited by coplanar waveguide for easy fabrication on one surface via screen printing. The defected ground structure was applied in an array element to improve the radiation and increase the gain. The results showed that the printed, single element graphene antenna produced an impedance bandwidth, gain, and efficiency of 48.64%, 2.87 dBi, and 67.44%, respectively. Meanwhile, the array element produced slightly better efficiency (72.98%), approximately the same impedance bandwidth as the single element (48.98%), but higher gain (8.41 dBi). Moreover, it provided a beam width of 21.2° with scanning beam capability from 0° up to 39.05°. Thus, it was proved that graphene materials can be applied in 5G. Over the next few years, researchers and scientists anticipate that the next communication technology—fifth generation cellular network technology 5G)—will have greater overall capacity and implement a new spectrum . The sysG—will haMuch effort has been put into achieving the requirements of 5G such as broadband dual-band antennas , multi-iPrior to this study, previous works on 5G antennas have been conducted, particularly on bandwidth, gain, and beam steering in terms of the projection of higher data rates, further distance, and reliable communications, respectively. Bandwidth improvement can be shown in many ways such as balun integration , coupled2 V−1 s−1 compared to other materials. It becomes an attractive material for the manufacturing of ultra-high speed electronics [In conjunction with the emergence of 5G, the properties of graphene have been considered in this work. Graphene is the thinnest two-dimensional layer of carbon atoms  bound inctronics  besides ctronics  or tunabctronics . The swictronics  or Diracctronics . This prctronics . Based octronics ,39,40,41ctronics , transpactronics , switchectronics ,44,45, ectronics , reconfictronics , tunablectronics , and beactronics , the opeBased on the 5G requirements and limitations aforementioned, this paper proposes the development of graphene antennas in single and array which operates at a frequency of 15 GHz for 5G applications. The 15 GHz frequency was selected since the range is at high frequency. Thus, it can produce large bandwidth to support higher speed . Note thThe structure of this paper is as follows: rε = 3.5, and tan δ = 0.002 at 1 kHz. The graphene used was from graphene dispersion with ethyl cellulose in terpineol, or commonly known as graphene ink, which has a sheet resistivity between 0.003 Ω.cm and 0.008 Ω.cm with a thickness near 100 nm. The antenna was printed by a screen-printing method and fed by a 50-Ω CPW. The top substrate was coated with the patch and ground plane. Then, the antenna was excited through CPW to achieve a large bandwidth [andwidth ,56, wherWp antenna size was estimated by Equation (1):c is the velocity of light, 3 × 108 m/s, οf is centre frequency, and rε is the dielectric constant of a substrate. Then, the distance of the separation between the two ground planes of the waveguide (CPW), Dcpw, was calculated by Equation (2) [s1 is the slot width between the ground plane and the feedline, and Wf is the centre strip conductor width or feedline width.Before optimisation, the patch width, tion (2) ,58:(2)DcThe antenna was simulated in Computer Simulation Technology (CST) Microwave Studio. The printed graphene antenna had a width and length of 12.2 mm and 11.8 mm, respectively, and a thickness of 76 μm. The details of the antenna parameters are summarised in Screen printing is a technique of printing design patterns from an ink solution onto a substrate surface through a mask using a squeegee rubber movement. The method has been widely used in electronic manufacturing ,64,65,66Related to the graphene ink which needs a curing process, a Kapton film was adopted as a substrate. This was due to the film’s unique combination of properties which make it ideal for variety of applications in many different industries . It alsoSeveral parametric studies were executed to observe the antenna’s performance and to identify problems. There are many factors that could disturb the accuracy of the antenna’s results which happen during the fabrication process and other technical works. During fabrication, the graphene ink was handled manually; thus, the antenna produced may have an inaccurate size for small parts. During the curing process, the temperature and time set may have affected the condition of graphene and substrate. Then, after the curing process was completed, the graphene antenna was cut using penknife where small defects may have been created.The parametric studies were the dielectric constant of the substrate, conductivity of the graphene, and cut length. These parameters were selected due to the fact of their significant influence on the frequency resonant. It was conducted by a single parameter which was varied while others were kept constant. The simulation results of the parametric studies are shown in 2 S/m to 3.33 × 106 S/m shifted the resonance frequency to the right by approximately 1.53 GHz, from 13.65 GHz to 15.18 GHz. Conductivity variation can also be caused by the heat treatment value or length of the curing process. The parametric study on the cut length is depicted in Lc, is a critical part of the fabrication process for the proposed screen-printed antenna.The curing process was needed to break the binder contained in the graphene ink, so that the conductivity would increase. The binder contained in graphene functioned to change the graphene flakes into ink solution and as an insulator . The conDisturbance was observed on the other type of graphene antenna with the same design and operating frequency. The two minor lobes that appeared in the radiation pattern at the E-plane for the antenna made with graphene ink also appeared in the antenna made by graphene sheet but to a smaller degree due to the higher conductivity, while, the radiation pattern at the H-plane for the graphene sheet was similar to the simulation. When graphene has a higher conductivity, it will not be disturbed by the adaptor and connector during radiation pattern measurement compared to graphene ink which does not have enough conductivity as stated in the manufacturer’s data sheet. Also, the graphene sheet does not go through a curing process which could affect the results. However, the radiation pattern of the graphene sheet was not included in this work.oe, was estimated through the calculation of the multiplication between the reflection (mismatch) efficiency, re, and the antenna radiation efficiency, cde [With the respect to the resonance frequency in graphene ink, the simulated gain value was 2.39 dBi, while the measured gain was 2.87 dBi. The total efficiencies obtained for the simulation and measurement were 65.25% and 67.44%, respectively. The total efficiency, ncy, ecd . The radS11 of smaller than −10 dB from 14.32 GHz to 15.87 GHz which covered the proposed frequency bands of 5G communication, while S12, S23, and S34 were −17.47 dB at 15 GHz. However, when each element of the printed graphene antenna array was combined with the adjacent element to form a 4 element and terminate in the same ground plane, the radiation pattern at the E-plane presented an omnidirectional pattern, while the H-plane deteriorated with higher side lobe level (SLL) at −9.6 dB, as shown in Wd, of 2 mm and length, Ld, of 10.8 mm in between adjacent elements were then introduced, as shown in S11 showed that the printed graphene antenna array had a frequency range of 14.30–15.71 GHz, where the impedance bandwidth was reduced to 140 MHz compared to the antenna array before introducing the rectangular slot, but it was still larger than 1 GHz which is enough for the 5G high data rate, while the mutual coupling was reduced by approximately −4.66 dB. Even though a small reduction occurred in the mutual coupling, a large effect showed up in the radiation pattern and gain, where a bidirectional pattern was exhibited in the E-plane and directive beam in H-plane, as shown in According to the radiation pattern deterioration, the mutual coupling of the adjacent elements should be reduced through a technique of defected ground structure (DGS) for the improvement of the radiation pattern. Rectangular slots with a width, d, and the progressive phase shift, β, can control the characteristics of the array factor and the total field of the array [AF) is given by Equation (3):n is number of elements, and θ is the angle observed.The variation of the inter-element spacing or separation, he array . The arrBased on Equation (3), the inter-element spacing was observed for the effect of the gain obtained on the printed graphene antenna array after introducing the rectangular slot. The variation of inter-element spacing was between 0.6λ and λ. The gain value increased from 0.6λ to 0.8λ, then decreased until λ. The gain versus inter-element spacing is plotted in S11 measurement via a performance network analyser and then for comparison with the simulated S11 as displayed in S11 were less than −10 dB in the frequency bands of 14.30 GHz to 15.70 GHz and 11.10 GHz to 18.30 GHz, respectively, which are included in the proposed frequency for 5G. The resonance frequency for the measured result was approximately the same as the simulation’s result, 14.78 GHz. However, some ripples appeared in the measured S11 due to the cable loss from the Re-Formable Semi-Rigid Cable Assemblies that were connected between the printed graphene antenna array and the external 1-to-4 power divider as depicted in S11 also had broad bandwidth compared to the simulation because of the unpredicted dielectric, conductivity or composition formed by the graphene ink after the curing process. For validation of the proposed designed, the printed graphene antenna array with a rectangular slot was fabricated as presented in Re-Formable Semi-Rigid Cable Assemblies were connected to the antenna array which were located at 90° during the rotation of the measurement as shown in The performance of the printed graphene antenna array with the rectangular slot was validated by measuring the radiation pattern. The simulated and measured normalised radiation patterns were plotted in the E-plane and H-plane at a respective frequency as shown in Theoretically, scanning phased array can be evaluated by Equation (4):The performances of printed graphene antennas were studied for single and array elements at 15 GHz. The 4 element antenna array was successfully fabricated by introducing a rectangular slot for reducing mutual coupling. From the results of the impedance bandwidth, antenna gain, and antenna efficiency, the printed graphene antenna at a single element fulfils the 5G requirement, on par with the array element which has high gain, a narrow beam, and is steerable. This tiny antenna is comparable with other thin film metals and offers another selection for alternative methods to produce smaller-sized antennas. The challenge in this work was to control the dielectric substrate and conductivity of graphene during the curing process which caused a slightly different result. In the future, the graphene antenna can be improved by using a higher conductivity graphene ink or the choice of graphene ink must not involve a curing process for maintaining conductivity and dielectric stability.


The metal-free synthesis of graphene on single-crystal silicon substrates, the most common commercial semiconductor, is of paramount significance for many technological applications. In this work, we report the growth of graphene directly on an upside-down placed, single-crystal silicon substrate using metal-free, ambient-pressure chemical vapor deposition. By controlling the growth temperature, in-plane propagation, edge-propagation, and core-propagation, the process of graphene growth on silicon can be identified. This process produces atomically flat monolayer or bilayer graphene domains, concave bilayer graphene domains, and bulging few-layer graphene domains. This work would be a significant step toward the synthesis of large-area and layer-controlled, high-quality graphene on single-crystal silicon substrates.The online version of this article (10.1007/s40820-017-0173-1) contains supplementary material, which is available to authorized users. Graphene was successfully grown on single-crystal silicon substrates using metal-free, ambient-pressure chemical vapor deposition.Atomically flat monolayer or bilayer graphene domains, concave bilayer graphene domains, and bulging few-layer graphene domains can be produced by controlling the growth temperature.In-plane propagation, edge-propagation, and core-propagation processes are proposed to evaluate the sequentially changing graphene domains.Graphene is a novel two-dimensional material with remarkable mechanical and electrical properties, such as high carrier-mobility and outstanding mechanical flexibility . Since t2 . D. D42]. DAt a higher temperature, both the hydrocarbon radicals and the silicon surface should become more active, and an additional layer of graphene forms on the active edge of the monolayer graphene domain. The growth mechanism of graphene changes to edge-propagation instead. Therefore, concave bilayer domains with larger size are formed, as depicted in Fig. n-type and p-type silicon). We found that the growth regimes of graphene are independent of the Si surface structure, further indicating that the direct growth of graphene on silicon is a self-propagating process and follows the van der Waals growth model. The growth of graphene on Si is mainly controlled by the temperature and the confined, local environment of the precursors.The growth of graphene was further explored using different orientations and doping types of single-crystal silicon substrates Below is the link to the electronic supplementary material.


In this paper, we propose a metamaterial structure for realizing the electromagnetically induced transparency effect in the MIR region, which consists of a gold split-ring and a graphene split-ring. The simulated results indicate that a single tunable transparency window can be realized in the structure due to the hybridization between the two rings. The transparency window can be tuned individually by the coupling distance and/or the Fermi level of the graphene split-ring via electrostatic gating. These results could find significant applications in nanoscale light control and functional devices operating such as sensors and modulators. Electromagnetically-induced transparency (EIT) is a concept originally observed in atomic physics and arises due to quantum interference, resulting in a narrowband transparency window for light propagating through an originally opaque medium ,2. The EGraphene is a two-dimensional material which is composed of single layer of carbon atoms, which has been widely used in optoelectronic devices, such as optical modulators ,29,30 duRecently, L.S. Yan et al. have investigated that a plasmonic waveguide system based on side coupled complementary split-ring resonators and the electromagnetic responses of CSRR can be flexibly handled by changing the asymmetry degree of the structure and the width of the metallic baffles . W. Yu e2O3 and the graphene split-ring is composed of 5 layers of graphene in our following simulations so as to enhance the modulation depth [1 whose material is gold as shown in 1 is negligible because of the relatively small size with respect to the structure. The incident light propagates in the z direction and its polarization is along x direction. Both the gold split-ring and graphene split-ring are symmetric in y direction and their symmetry axis are coinciding. The (complex) refractive index of Al2O3 is obtained from Table I, page 662 in Ref. [18cm−3 and its refractive index can be obtained from Ref. [2O3 and doped Si have been considered having the dispersion and absorption effects in our simulations.As shown in on depth . The bot in Ref.  and the rom Ref. . Both thσ(ω) is dominated by interband and intraband transitions within the random-phase approximation, which can be calculated as [ω is the optical angular frequency, T is the ambient temperature (300 K in this paper), fE is the Fermi level of graphene, ħ = h/2π is the reduced Plank’s constant, Bk is the Boltzmann constant, τ is the carrier relaxation time and τ = ħ/2Γ [Γ is the scattering rate and it is set 0.00099 eV in this paper (corresponding to the carrier relaxation time τ ≈ 0.33 ps). It can be seen from the above formula that the surface conductivity is greatly affected by the Fermi level and the Fermi level is determined by the carrier concentration gn and Fermi velocity fV. The formula fE = f(πng)ħV1/2 with the Fermi velocity of fV = 106 m/s can be obtained from Ref. [gn = ε0dVgε/eH1, where gV is the applied voltage and dε is the permittivity of Al2O3 and H1 is the thickness of Al2O3. In the following simulation, graphene is modeled as a thin anisotropic material film and the in-plane permittivity is approximated to be [gt is the thickness of graphene which is estimated as 1 nm [0ε is the permittivity in vacuum. In addition, the conductivity of the N-layer graphene is Nσ [The optical properties of the gold material are obtained from Palik’s experimental data. The surface complex conductivity of graphene lated as ,45:(1)σεg=1+ as 1 nm  and ε0 ine is Nσ ,50.In this paper, we use the finite-difference time-domain (FDTD) simulations to numerically investigate the properties of the structure. The perfectly matched layer (PML) absorbing boundary conditions are set on the z direction while the periodic boundary conditions are set on the x and y directions.fE of the graphene split-ring is set as 0.9 eV and the coupling distance d is 20 nm. From the transmission spectra in To demonstrate the EIT effect, we numerically calculate the simulated transmission spectra of the unit cell with the graphene split-ring and the gold split-ring are shown in d is 20 nm. It can be observed that dip II is obviously blue-shifted from 7.97 μm to 4.35 μm while dip I blue-shifts slightly and its transmittance increases with the layers of the graphene split-ring N increasing from 1 to 5. In addition, it is clear shown that the transmission peak is blue-shifted and the line width of the transmission peak becomes smaller and narrower. This is because the hybridized of the gold split-ring and graphene split-ring become stronger with increasing the layer number N. It is also found that 4 layers or 5 layers of the graphene split-ring are suitable. Here we choose the graphene split-ring of 5 layers because the quality factor of transmission peak is larger than that of the 4 layers. In Then, we study the response of EIT effect resulting from the variation of the layers of graphene split-ring a and thed between the two rings. As shown in d. When d comes to 400 nm, the peak will disappear. It reveals that the interaction of gold split-ring and graphene split-ring becomes weaker and their interaction eventually disappears when the coupling distance is large enough. It can also find that dip I red-shifts slightly while the dip II blue-shifts with the increase of d and both their transmittance decrease. Therefore, the coupling strength of the metamaterial structure greatly depends on the distance of the gold split-ring and graphene split-ring.Furthermore, we also investigate the dependence of the EIT spectra on the distance λ = 3.83 μm) and wavelength II (λ = 4.35 μm) are shown in d is 20 nm, and the Fermi level of graphene split-ring is 0.9 eV.To get further insight into the physics of the EIT phenomenon of our structure, the electric-field distributions of the z-component at wavelength I (d is small enough, their local surface plasmons will couple to each other, which is analogous to σ hybridization of p orbital electron in the atomic outer layer. From λ = 3.83 μm. In contrast, the positive and negative induced charges are distributed on the left and right sides of the graphene split-ring. The different charge distributions of the two rings are similar to the anti-bonding mode of the hybrid molecular system. On the other hand, one can find that the distribution of induced change in the gold split-ring remains unchanged at the wavelength λ = 4.35 μm, while the distribution of induced change in the graphene split-ring is opposite to the situation at λ = 3.83 μm from The placement of graphene split-ring and gold split-ring can be treated as asymmetric nanoparticle dimer which has been investigated in Ref. . When d f1/2λ~1/E [As mentioned earlier, the complex surface conductivity of graphene can be changed by controlling its Fermi level, which can be realized by applying different gate-voltages to the graphene split-ring. Compared with the reported bright-bright mode coupling EIT structure fabricated by metallic material, we can realize the dynamically control of the EIT window in our metamaterial structure without reconstructing the geometries or imbedding other actively controlled materials. ~1/Ef1/2 . At the In this paper, we have successfully proposed that the EIT effect can be realized through bright-bright modes coupling in the MIR regions. The EIT window appears due to the hybridization between the gold split-ring and graphene split-ring and it is sensitive to the coupling distance. Moreover, we investigate the response of EIT effect resulting from the variation of the layers of graphene split-ring and periods in the x direction. Particularly, the EIT window can be dynamically tuned by adjusting the Fermi level of the graphene split-ring instead of reconstructing the structure. These properties could lead to new opportunities for many important applications, such as sensors and slow light modulators in MIR regions.


In this paper, we report the molecular docking study of graphene oxide and glucose oxidase (GOx) enzyme for a potential glucose biosensing application. The large surface area and good electrical properties have made graphene oxide as one of the best candidates for an enzyme immobilizer and transducer in the biosensing system. Our molecular docking results revealed that graphene oxide plays a role as a GOx enzyme immobilizer in the glucose biosensor system since it can spontaneously bind with GOx at specific regions separated from the active sites of glucose and not interfering or blocking the glucose sensing by GOx in an enzyme-assisted biosensor system. The strongest binding affinity of GOx-graphene oxide interaction is −11.6 kCal/mol and dominated by hydrophobic interaction. Other modes of interactions with a lower binding affinity have shown the existence of some hydrogen bonds (H-bonds). A possibility of direct sensing (interaction) model of glucose by graphene oxide (non-enzymatic sensing mechanism) was also studied in this paper, and showed a possible direct glucose sensing by graphene oxide through the H-bond interaction, even though with a much lower binding affinity of −4.2 kCal/mol. It was also found that in a direct glucose sensing mechanism, the sensing interaction can take place anywhere on the graphene oxide surface with almost similar binding affinity. T network ,7,8,9,10 network , gas ads network , and opt network . The larThe large surface area combined with a very good electrical conductivity has made graphene-based biosensors powerful in terms of sensing accuracy and selectivity. The excellent biocompatibility and non-toxic properties also favor graphene for biosensor applications. Utilizing graphene in biosensing system requires incorporation of other materials to build a graphene composite or thin film electrodes. Some materials such as Nafion, polyaniline, and gold nanoparticles have been combined with graphene to immobilize the enzyme and to facilitate the electrochemical sensing mechanism. Some applications of graphene in biosensors include cholesterol detection ,15, DNA The use of graphene in glucose biosensing systems has been utilized intensively for more than a decade. There are two methods of glucose biosensing widely known, first the enzyme-assisted, and second, the non-enzymatic (direct) mechanism. For the enzyme-assisted method, researchers have focused on synthesizing the graphene nanocomposite system using various combinations of materials  to immobilize the glucose oxidase enzyme and to facilitate the electrochemical process in the biosensors . Fu et aThe molecular docking method is a computational approach to analyze the receptor-ligand interaction by utilizing a rigorous physical concept combined with the optimization and statistical method. Through a docking method, we can have a good prediction on the likelihood of a particular molecule in making a complex with another molecule. There are two types of docking, rigid docking, and flexible docking. In this paper, we use a rigid docking where the target structure is rigid, while the ligand structure is flexible. The docking simulation of graphene oxide with glucose oxidase in this paper was inspired by the experimental work by Wang et al. , where td-glucose. Secondly, we assume that the interaction between GOx with graphene oxide will not change the conformation of GOx in its native state and do not interfere with the glucose sensing process in the active sites of GOx. Although in reality the binding of graphene oxide with GOx enzyme in an aqueous condition most likely will change the enzyme’s conformation, but for the simplicity we assumed here that the adsorption of enzyme on graphene oxide surface is solely based on rigid docking calculation, without considering the dynamics of the complex in a particular environment (solvent). Further evaluations and more precise simulation of GOx-graphene oxide complex’s structural integrity through a molecular dynamics simulation [d glucose) molecule directly interacts with graphene oxide. The binding affinities and binding sites of this mechanism are our interest.The aim of this research is to elucidate the molecular interaction between graphene oxide with GOx enzyme and glucose with graphene oxide to explore the graphene oxide’s potential in a biosensing system, whether as an enzyme immobilizer or as an active sensing material. There are some assumptions made at the beginning of this research. Firstly, we focus on the molecular interactions between graphene and GOx enzyme and not delving too much into the interaction between graphene and other materials, such as Nafion, polyaniline, gold nanoparticles, and etc. The blind docking method was chosen to enclose the whole surface of GOx enzyme and to identify the binding sites of graphene oxide as compared to the binding (active) sites of β-mulation  and molewww.rcsb.org with PDB code of 1CF3 [Aspergillus Niger bacteria. The enzyme structure was cleaned from water molecules, natural ligand, and other residual substrates using the Chimera program [*.pdb format. The docking preparations for the enzyme receptor were done using Autodock Tools ADT 1.5.6 [*.pdbqt format. The structure of the enzyme receptor and the graphene oxide are shown in The structure of glucose oxidase for the enzyme receptor was downloaded from  of 1CF3 . This en program , then itDT 1.5.6 . In this*.sdf format from https://pubchem.ncbi.nlm.nih.gov. The 2D structure then converted into a 3D structure using an online server at https://www.mn-am.com/online_demos/corina_demo. As we know, there are three kinds of graphene, pristine graphene, graphene oxide, and reduced graphene oxide [*.pdb format using Chimera. The polar hydrogen bonds and the Gasteiger charges were added to the ligand before it was saved in the *.pdbqt format by using Autodock tools ADT 1.56. The two-dimensional structure of graphene oxide (PubChem CID:124202900) was downloaded in the Since there is only limited information regarding the binding of graphene oxide on GOx, we had to perform a blind docking method to identify the possible binding modes. The blind docking was performed using Autodock Vina software  to find The sensing mechanism of glucose by GOx can be expressed asd-glucose into d-glucono-1,5-lactone, which is then hydrolyzed to gluconic acid and hydrogen peroxide (H2O2). The hydrogen peroxide then dissociates into 2H+, O2, and two free electrons, which can be captured by the electrode and measured by the electronic instrument [The glucose oxidase enzyme catalyzes the oxidation of β-strument . The send-glucose, the sensing mechanism as explained by Equation (1) was not disturbed and still took place. In this mechanism, graphene oxide was acting as an enzyme immobilizer which facilitates, and not interferes with the glucose sensing activity by GOx enzyme.In this proposed biosensing system, the graphene layers were attached to the cathode (by coating technique) and expected to bind with GOx enzymes with some kind of non-covalent interaction at particular binding sites. By assuming the GOx-graphene oxide interaction occurred at a different pocket as compared to the active sites of β-d glucose are GLU 412, HIS 516, HIS 559 [d glucose and negates the possibility of using graphene in biosensing applications. On the other hand, if graphene does not interact with the active sites of glucose, then graphene acts as a non-competitive ligand to glucose and can be used as a GOx enzyme immobilizer in an enzyme-assisted biosensor, such as in [The catalytic sites of GOx enzyme which interacts with β- HIS 559 . Throughch as in . The AutIt was found that mode 1 to 3 have almost similar binding sites see , while mUnlike mode 1, the binding affinity of mode 3 is slightly weaker . There are 18 residues involved in the hydrophobic interaction in addition to two residues involved in H-bond interaction. Two H-bonds (double bonds) present in mode 3, with one H-bond, occurred in GLY 169 (H-bond distance of 3.149 Å), and one in ASN 168 (H-bond distance of 2.859 Å) as seen in d glucose) sensing by the graphene oxide through a simulation approach. We performed a blind-docking method to explore any possible interaction between the glucose molecule with the surface of the graphene oxide layer. The docking simulation was set by the grid box size of x = 30 Å, y = 24 Å, and z = 26 Å, and the origin point at x = 0.135, y = 0.041, and z = 0.018. The number of modes and exhaustiveness were set to 20 and 16 respectively. The docking results of this non-enzymatic sensing model are shown in The large surface area has made graphene oxide very promising for biosensor applications due to its superior electronic and electrochemical properties . Some red-glucose and graphene oxide. The strongest interaction (mode 1) has the binding affinity of ΔG = −4.2 kCal/mol, while the weakest (mode 20) has ΔG = −3.7 kCal/mol . From 20 binding modes, only mode 1 and 8 which have H-bond interactions. In mode 1, one H-bond is identified with a distance of 2.262 Å. Mode 8 has two H-bonds, each with a distance of 2.023 and 2.236 Å  interaction with a small portion of a strong non-covalent (H-bond) interaction presents. Since graphene oxide binds in the different pocket than β-d-glucose, the binding of GOx and graphene oxide will not interfere the glucose sensing process in the active sites of GOx . At this stage of research, we only consider the binding between graphene oxide and GOx enzyme. The point mutation effect on the particular amino acid of GOx enzyme will definitely change the enzyme adsorption at the graphene surface, since the adsorption free energy of each amino acid is different. A molecular dynamics simulation will be conducted in the future to reveal the conformational ensemble of the adsorbed enzyme as shown by [d-glucose and graphene oxide shows a promising application of graphene oxide layer as an active biosensor material through a non-enzymatic mechanism. The relatively the same binding affinity of β-d-glucose on graphene oxide , regardless of the position of interaction on the graphene oxide surface, offers an almost uniform glucose-probing sensitivity of the graphene oxide layer. Despite a much weaker binding affinity of β-d-glucose with graphene oxide as compared to the GOx-graphene oxide binding, the large surface area of graphene oxide with relatively the same sensitivity makes graphene oxide also promising to be developed into a non-enzymatic biosensor. The direct glucose sensing simulation here is only a preliminary study of a possible direct biosensing mechanism, where glucose (β-d glucose) molecules directly interact with graphene oxide. Further study must be done on this subject in the future. Unlike the drug discovery research where a high throughput virtual screening with multiple docking is common, the multiple docking of various analytes with graphene (or graphene oxide) to study the graphene’s selectivity, to the best of authors knowledge, has never been found in the literature and would be interesting to do in future.In this work, we have performed a molecular interaction analysis based on the molecular docking results to explore the potential of graphene oxide in glucose biosensing applications. Two mechanisms were simulated in this paper, first the enzyme-assisted mechanism and second the non-enzymatic (direct) mechanism. Based on the simplified docking parameter assumptions used here, which in some cases might be favorable compared to experimentally achievable results, molecular docking analysis has revealed that graphene oxide can be used as an enzyme immobilizer as shown by its strong binding affinity  and its binding sites which do not overlap with the active sites of β-shown by . The mol


This article is about managing flood disasters affecting the built environment in the rural communities of Zimbabwe. Using Tsholotsho district in Matabeleland North province as a case study, the authors argue that flooding has adversely impacted the built environment through destroying infrastructure. The principal objectives of this study were to establish the impact of flood disasters on the built environment, to demarcate factors that perpetuate communities’ vulnerabilities to flooding and to delineate challenges that negate the management of flood disasters in the built environment. This qualitative study was based on a purposive sample of 40 participants. Data were collected through semi-structured interviews and observation methods. The findings were that floods can damage human shelter, roads, bridges and dams. Locating homesteads near rivers and dams, using poor-quality construction materials, and lack of flood warning were found to perpetuate vulnerability to flooding. Poverty and costs of rebuilding infrastructure, lack of cooperation between the communities and duty-bearers, and failure to use indigenous knowledge were found to be impeding the management of flood disasters. The study concluded that flood disasters can wipe out community development gains accumulated over many years. Further, community vulnerability to flooding in the built environment is socially constructed. The study posits that addressing the root causes, reducing flood vulnerability and avoiding risk creation are viable options to development in the built environment. Lastly, reconstruction following flood disasters is arduous and gruelling, and not an easy exercise. Flood disasters have a propensity to impact the built environment and cause huge losses through destroying property, including buildings and infrastructure Cigler . EvidencThis study focuses on managing flood disasters on the built environment in Tsholotsho district, south-west of Zimbabwe. The principal objectives of the study are threefold, namely, to establish the impact of flood disasters on the built environment, to demarcate factors that perpetuate vulnerability to flooding and to delineate the challenges that negate the management of flood disasters impacting the built environment.The management of flood disasters in Tsholotsho district in the Matabeleland North province, south-west of Zimbabwe, has not been effective enough to save the built environment. Of late, the district has been inundated by destructive flooding events. The floods have severely impacted the built environment, damaging human shelter among other forms of infrastructure. Communities most affected have been those located along the Gwayi, Zombani and Manzamnyama rivers, and communities settled near Gariya and Bhudani dams. The Government of Zimbabwe has at times tried to restore the damaged shelter and infrastructure through some reconstruction processes. However, following subsequent severe flooding, the built environment has always experienced the same impact of being destroyed by the forceful floods. As such, it is imperative that the government comes up with new robust measures that can save the built environment. Such measures have a potential to benefit the communities through minimising the impact of future flooding events. If no meaningful measures are taken by the duty-bearers to deal with the impact of flooding on the built environment in the district, the communities will continue to suffer huge losses. Such losses may even be permanent, considering that many communities in rural districts are poor, with little or no means to recover from disaster impact Cigler .This section of the article reviews the literature relevant to the study. The literature is interrogated and discussed in a manner that agrees with the study’s objectives. The first objective focuses on the impact of flood disasters on the built environment.Globally, flood disasters of various magnitudes have continued to severely impact the built environment. According to Lindell , disasteCertain factors may perpetuate communities’ vulnerability to flooding, leading to disaster occurrence in the built environment. This study chose the three common aspects of flood vulnerability, namely, use of poor building materials and communities’ failure to adhere to building codes, sociological aspects of communities and cultural beliefs. These factors were chosen because they were believed to be the major drivers contributing to flood disasters in modern societies. Mudavanhu  posits tPrevious studies on disaster risk reduction have shown that structures constructed using poor, non-durable construction materials are vulnerable to flood hazards. Therefore, players in the construction industry are encouraged to carefully choose building materials when constructing structures. Substandard building practices are understood to aggravate flood disaster impact on the built environment. Deficiencies, which manifest in the failure to enforce building codes, if not addressed, may prevail even in the post-flood disaster reconstruction period. Vulnerability to flooding in the built environment can, therefore, be reduced through the building of resilient structures, through regulating social behaviours, and through the provision of adequate early warnings, among other strategies Pelling . ApproprSatterthwaite et al.  note thaSocial setting of communities is another factor that can influence flood disasters within built environments. Sociological aspects and configurations of communities can worsen some people’s vulnerabilities and fuel the intensity of flooding events The findings in Three major factors were found to have contributed to and perpetuated flood vulnerability, and flood disasters in the built environment of Tsholotsho district. According to the interviewees, such factors include location of homesteads near rivers, dams and other water basins – which was most mentioned (25.0% – 62.5%), followed by use of non-durable or poor-quality construction materials (10.0%– 25.0%) and lack of timely flood warning (5.0% – 12.5%). These factors are discussed in detail in the subsection ‘Homesteads located near rivers, dams and other water basins’.Homesteads located near rivers and dams proved to be the major factor perpetuating flood vulnerability in the district. Of the interviewed flood victims, 62.5% were of the view that had their settlements been sited away from the rivers and dams, they would have been free from flood risk. This can be interpreted to mean that the communities settled in flood-prone areas were aware of the dangers facing them, but just ignored them. As such, disasters can impact even those communities with enough disaster knowledge and awareness if no proper measures are taken. Through the researchers’ observations, it was also noted that some villagers in Wards 5 and 6 were located very close to the Zombani and Gwayi rivers respectively, while those in Ward 8 were situated close to Gariya and Bhudani dams. One villager narrated how during the rainy season, water from the Bhudani dam would overflow into their homesteads:‘During rainy seasons, water overflows to our homesteads when Bhudani dam is full. This situation has resulted in the community losing some property in the form of huts, barns and school buildings in addition to the destroyed dam wall’. The above findings concur with a study conducted by Parker, Little and Heuser , who fouApart from building their homesteads in flood-prone areas and near rivers and dams, communities were observed to have used non-durable materials for building their structures. Some respondents (10.0% – 25.0%) thought their flood vulnerability was worsened by weak materials used in the construction of shelter (huts and houses), roads, bridges and dam walls. Dwelling structures, according to the respondents and complemented by observations, were constructed from pole, mud and thatch. This type of building material was observed to be inferior and prone to flood damage. The continued use of such material in Tsholotsho district suggests that the district might continue to be a breeding place for flood disasters. Poor workmanship in the construction of bridges was observed by the researchers.One such bridge which was observed to have been damaged by the floods was a small bridge crossing Zombani River in Siphepha area. The bridge was completely washed away by flood waters, rendering it dangerous and unusable. Crossing places along rivers need to be constructed using durable material that does not endanger the lives of the rural communities. The findings are in line with results from Sharma and Joshi , who fouLack of flood awareness within the communities was found to be another factor contributing to flood vulnerability in Tsholotsho district. Some respondents (5.0% – 12.5%) highlighted that most people lacked sufficient information on impending flood hazards, resulting in being caught unawares. The respondents were of the opinion that lack of flood awareness contributed to their ignorance about flood hazards, hence their increased vulnerability to flooding. Their argument was that communities with enough flood awareness would rarely be caught unaware during periods of severe flooding. Respondents felt that flood awareness programmes should be undertaken within the communities, and that these programmes would make known flood hazards existing within their vulnerability contexts. One respondent had this to say:‘We want the responsible authorities, especially the District Civil Protection Unit, to come down here to the communities and provide flood awareness programmes. People living in this part of the district do not have enough information concerning their vulnerabilities to flooding, hence our continued suffering’. However, the study further established from the respondents that awareness campaigns had been provided by the Tsholotsho District Civil Protection Unit (DCPU), although they have been few. From the respondents’ narrations, provision of timely flood awareness by the DCPU may enhance their capacity to prepare for flooding events in the district. As such, this study interprets that the DCPU and its partners are not effective enough to serve the communities well. Disaster knowledge is an empowerment tool against flooding, and communities should possess such knowledge in advance and in abundance (Fabiyi & Oloukoi Three major issues were found to negate the management of flood disasters in the built environment of Tsholotsho district. As highlighted by 20 out of 40 (50.0%) respondents, poverty and cost of rebuilding infrastructure, followed by lack of cooperation between communities and duty-bearers (15.0% – 37.5%), and failure to properly use indigenous knowledge (5.0% – 12.5%) were found to be the main challenges affecting the rebuilding processes.The majority of people in places affected by the floods in Tsholotsho district, as highlighted by the respondents, are peasant farmers, most of whom are languishing in poverty. This study views poverty as being based on the evaluation of the economic or income status of individual members of the community People expect the responsible governments to help them to recover from disasters. Therefore, the government as the main duty-bearer should not impose humanitarian aid on the communities without proper consultation. These results support findings from previous research found in the extant literature. For example, Cannon, Twigg and Rodwell (2003:10) showed that communities and organisations that have cooperated successfully were in a position to assist each other and other groups during disaster events. Lack of cooperation between the communities and the duty-bearers can result in a situation where flood-impacted communities find themselves in worse conditions.inkanku (a bird associated with forecasting rains), cloud patterns and changes in certain indigenous trees. The respondents believed such indigenous knowledge helps them to predict rains with a potential for flooding. From the researchers’ interpretive point of view, the use of indigenous knowledge by the residents is symbolic of the norms, culture and beliefs prevailing in many African communities. It also shows the value that African communities attach to their cultural beliefs and how their culture shapes their daily lives. These findings are consistent with the results of a study by Domfeh (Members of the community living with flood risk were found to command indigenous knowledge for dealing with floods. According to the respondents, they were able to use home-grown knowledge to forecast rainy seasons with a potential to cause flooding. This guided them in taking appropriate action in preparation for flooding. The respondents narrated how they studied and interpreted the behaviour of certain animals and birds to forecast the magnitude of rains. They studied the behaviour of y Domfeh  on indigAlthough the knowledge generated from the local communities is of utmost relevance, the respondents felt that their knowledge was underrated by the DCPU and other players. The respondents thought that local communities should be allowed to contribute their knowledge in managing flood disasters. The authors interpret this as low-rating of indigenous knowledge compared to Western knowledge. Again, disaster risk reduction practitioners see no potential value of indigenous knowledge as an effective tool for flood disaster management. However, the respondents were of the opinion that their indigenous knowledge should be integrated with modern knowledge, so that both spheres of knowledge become more effective. Their argument was that as the practitioners fall short of using indigenous knowledge that communities possess, infusing the two types would be a positive step.Drawing from the findings and conclusions, the authors recommend duty-bearers to assist flood-impacted communities with the means of restoring their built environments. Duty-bearers should assist communities with material for rebuilding of flood-resistant structures. In addition, regular flood awareness is to be undertaken to alert the communities in flood-prone areas. Lastly, duty-bearers should consider integrating indigenous knowledge of the communities with modern knowledge in disaster issues.This article concludes that flood disasters can impact the built environment through damaging infrastructure. Therefore, flood disasters have a propensity to wipe out community development gains accumulated over many years. The article further concludes that perpetuation of flood vulnerability in the built environment is an avoidable social construct created through people’s interaction with their environment. This study views the build-back-better concept as viable option to development in the aftermath of flood damage. However, challenges exist that may impede the management of flood disasters affecting the built environment. Finally, the study concludes that reconstruction following flood disasters is difficult and arduous.


Drug‐resistant bacterial infection is a global threat to public health due to the high mobility of the population. Novel therapy methods have been intensively studied for the eradication of antibiotic‐resistant bacteria, including photothermal treatment, which has established outstanding bacterial killing efficiencies under laser radiation, and superhydrophobic surfaces have exhibited excellent antifouling properties. However, an effective, scalable, and affordable bactericidal coating for eliminating drug‐resistant bacteria is lacking. Herein, a novel graphene coating using one‐step laser‐induced graphene and simultaneous laser‐induced forward transfer is introduced. The graphene coating shows high photothermal conversion and superhydrophobic performance, and these synergistic effects can make the bacteria number decrease with over 99.99% proportions under one sun illumination. The superhydrophobic properties can also reduce 99.87% of bacteria compared to the control sample when the solar energy is not available. This additive and scalable method can quickly coat functional graphene onto various substrates, with bacterial applications in many areas, such as water pipeline robots. A synergistic antibacterial graphene coating is developed for water pipeline robotics and has superhydrophobic and photothermal effects. Solar energy is more abundant and can be used for larger area bacteria eradiation compared to NIR laser. Photothermal sterilization was also proven using Prussian blue nanocages under solar irradiation.E. coli. This additive manufacturing method is scalable and affordable, and can be used in real‐world applications, such as antibacterial coatings for water pipeline robots.Recently, we developed a novel and scalable method for the fabrication of large area graphene materials with superwetting and photothermal properties. Ultra‐high specific capacity supercapacitors have been fabricated using this laser induced forward transfer (LIFT) strategy.2FigureThe LIFT deposition process is schematically illustrated as shown in FigureThe surface energies of graphene are estimated using static contact angle measurement, in comparison with polydimethylsiloxane (PDMS) and glass substrates. The pristine PDMS substrate displayed hydrophobic behavior with a contact angle at 117°, as shown in Figure−2. The temperature increased up to 55 °C after the initial 2 min and stabilized around 60 °C after 10 min, as shown in the red curve in Figure The photothermal effect of graphene compared to PDMS and glass substrates was explored, as shown in E. coli colonies within agar plates were grown on pristine PDMS, pristine glass substrate, and graphene coated glass to examine the antibacteria effects, as illustrated in FigureIn combination with the outstanding superwetting and photothermal properties of such graphene, the synergistic antibacteria performance was examined. The E. coli colonies formed on the agar plates were examined with optical photos and electron microscopy. The optical images of the E. coli colonies on various substrates without solar treatment were characterized using 107 dilution folds. Large numbers of E. coli colonies were observed in both the pristine PDMS . As shown in the field emission SEM, the dense biofilms of E. coli were clearly observed on the PDMS  medium containing 50 mg L−1 kanamycin overnight at 37 °C before use. Then, these E. coli cells were diluted by PBS to prepare the suspensions with optical density at 600 nm (OD600) reaching 0.6. Then, 200 µL E. coli suspensions were used to be incubated on the surface of gelatinous LB agar plates (diameter = 10 cm) containing 1.5 wt% agar at 37 °C for 12 h. Ideally, E. coli cells can totally occupy all the surface. Samples (PDMS/Glass/Graphene) were then incubated with the E. coli‐occupied surfaces at 37 °C for 12 h in the dark whilst one more glass sample was set in each agar plate for the thickness control of E. coli cells. All the samples, except the thickness control, were subjected to 10 min solar treatment on white paper.The E. coli cells were detached from the samples and resuspended into PBS. After appropriately dilution by PBS, these E. coli suspensions were placed on gelatinous LB agar plates (diameter = 10 cm) containing 1.5 wt% agar at 37 °C for 18 h. Consequently, each living cell can develop into a distinct colony after incubation and the number of living E. coli cells was estimated by the visible colony numbers on the agar plates. All the experiments were performed independently twice, while the colony counting was operated in triplicate.For SEM imaging, the above samples were soaked in liquid nitrogen prior to the following treatment. For colony counting assay, all the samples including the thickness control, were transferred to centrifuge tubes filled with 10 mL PBS. After 10 min shaking and 1 min sonication at 37 °C, the The authors declare no conflict of interest.SupplementaryClick here for additional data file.


In this study, a novel biobased poly(ethylene brassylate)-poly(furfuryl glycidyl ether) copolymer (PEBF) copolymer was synthesized and applied as a structure-directing template to incorporate graphene and 1,1′-bismaleimide (BMI) to fabricate a series of self-healing organic/inorganic hybrid materials. This ternary material system provided different types of diene/dienophile pairs from the furan/maleimide, graphene/furan, and graphene/maleimide combinations to build a crosslinked network via multiple Diels–Alder (DA) reactions and synergistically co-assembled graphene sheets into the polymeric matrix with a uniform dispersibility. The PEBF/graphene/BMI hybrid system possessed an efficient self-repairability for healing structural defects and an electromagnetic interference shielding ability in the Ku-band frequency range. We believe that the development of the biobased self-healing hybrid system provides a promising direction for the creation of a new class of materials with the advantages of environmental friendliness as well as durability, and shows potential for use in advanced electromagnetic applications. During the past decade, the development of self-healing substances has become an important research field since these smart materials bear resemblance to the living organisms which possess an intrinsic capability to repair their architectural damage via an automatic process without additional intervention. So far, several approaches have been developed to efficiently provide the self-healing property to fabricated materials, such as microcapsules ,2,3, micAmong these reversible self-healing methodologies, a dynamic-covalent bond technology based on Diels–Alder chemistry has received a great deal of attention since the deformation of the crosslinked molecular structure can be easily triggered via a heating process, resulting in a liquification of the polymer material to rebuild the crack area. In most cases, DA type self-healing materials were prepared by combining furan and maleimide functional groups serving respectively as diene and dienophile moieties to form a thermally reversible crosslinked network through a [4 + 2] cycloaddition reaction ,30,31,32Recently, increasing attention is given to sustainable chemistry with the goal to reduce dependence on fossil feedstock and develop alternative polymers from renewable biomass sources ,47,48. I3/g and size distribution of 5.6 to ~18 μm was supplied by Taiwan Graphene Co., Ltd. . Ethylene brassylate  and furfuryl glycidyl ether  were purchased from Sigma-Aldrich  and Acros , respectively. These two monomers were used as received. Furfuryl alcohol , 1,5,7-triazabicyclo[4.4.0]dec-5-ene  and 1,1′-bismaleimide  were purchased and used as received. Additionally, all the solvents for this study were purchased from Sigma-Aldrich and used without any purification.Graphene with a specific surface area ≥15 m−1) was prepared by dissolving the copolymer in THF solvent, followed by mixing with graphene in different weight fractions of graphene to PEBF of 1 wt %, 2 wt % and 5 wt %. The mixtures were then subjected to a bath sonication for 12 h. Afterward, BMI was added to the PEBF/graphene solutions based on a molar ratio of furan group to maleimide group of 1:1. After mixing for 24 h, the solutions were dried in ambient condition for 48 h. The obtained bulk samples were then placed in a vacuum oven and heated to 180 °C. After heating at 180 °C for 2 h, the hybrid samples were subsequently cooled to 60 °C and then isothermally annealed at 60 °C for 24 h. In addition to the PEBF/graphene/BMI hybrid samples, a self-healing PEBF/BMI sample without graphene was also prepared by following the similar route of the PEBF/graphene/BMI hybrids.First, a PEBF solution  with deuterated chloroform as the solvent. To analyze the molecular weight characteristics of the PEBF copolymer, size exclusion chromatography (SEC) analysis was conducted using a Viscotek TDA 305 system  equipped with a refractive-index detector. THF solvent was used as the mobile phase with a flow rate of 1.0 mL/min, and the measurement was operated at a temperature of 35 °C. Raman analyses were performed by using a Dongwoo Ramboss 500i Micro-Raman/PL spectroscope . For the Raman measurements, thin film samples were prepared by depositing hybrid solutions onto silicon wafer substrates, followed by drying in air for 12 h. The morphologies of the samples were investigated by using a Hitachi H-7650 transmission electron microscopy  operating at 75 kV. ATR–FTIR spectra were recorded on a Jasco FT/IR-4600 spectrometer , and flat bulk samples were used for the measurements. Wide-angle X-ray scattering (WAXS) measurements were carried out on beamline 13A1 of the National Synchrotron Radiation Research Center (NSRRC). Bulk samples with 1 mm thickness were used for the WAXS measurements and the incident X-ray was configured with a wavelength of 1.033 Å. TGA measurements were performed on a Hitachi STA7200 instrument  to analyze the thermal stability of the hybrid system. The sample was heated from 50 to 600 °C at 10 °C/min under nitrogen atmosphere. The thermal properties of the hybrid system were also characterized using a TA Q20 differential scanning calorimeter . The measurements were conducted by heating the sample from 50 to 200 °C at 10 °C/min. A Nikon ECLIPSE LV100N POL microscope  with a Linkam THMS600 hot stage  was used to image the self-healing behavior of the hybrid system. Additionally, scanning electron microscopy (SEM) micrographs were captured by using a Hitachi TM4000 Plus instrument  operating at 20 kV accelerating voltage to monitor the morphologies of the hybrid samples. The EMI shielding performance of the hybrid system was analyzed by the waveguide method using a vector network analyzer  in Ku-band frequency range (12.4~18 GHz). A rectangular bulk sample with dimensions of 16 mm × 8 mm × 3.5 mm was placed between the waveguide holders, and the S parameters  were measured to calculate the EMI shielding effectiveness.For identifying the molecular structure of the synthesized polymer, −1 and a molecular weight distribution of 1.51, indicating the successful synthesis of PEBF. 1H-NMR measurement was further performed to characterize the PEBF sample. As shown in 1H-NMR spectrum, the EB to FGE ratio in the PEBF copolymer was estimated to be 77% by calculating the integrated area ratio between the proton signal of furan ring and methylene protons (δ = 2.3 ppm) neighboring the carbonyl group of EB.The schematic illustration for synthesizing the PEBF copolymer system is shown in −1 and a tangential band (G band) at 1582 cm−1. The relative intensity ratio between the D band peak to the G band peak (ID/IG) corresponded to the bonding transition of graphene from C–C (sp2) to C–C (sp3), indicating the degree of structural defects on the graphene sample. In contrast to the Raman spectrum of the pristine graphene which exhibited a ID/IG value of 0.12, the Raman profile of the PEBF/graphene sample revealed a higher value (ID/IG = 0.19). This sudden change indicated the increase of graphene defects resulted from sp2 to sp3 hybridized carbons, providing the evidence for the occurrence of DA reaction in the PEBF/graphene hybrid. This structural integrity of PEBF attached to the surface of graphene was further confirmed by comparing the solubility of the PEBF/graphene sample and pristine graphene in solvent medium. For the investigations, the PEBF/graphene and pristine graphene were separately added to THF to prepare 0.05 wt % solutions, followed by a sonication for 30 min to disperse these materials in the liquid phase. The prepared solutions were then stored in an ambient environment. The dispersion conditions of these solutions were examined as a function of storage time, as shown in On the basis of the sample preparation method described above, the self-healing PEBF/graphene/BMI hybrid system was fabricated by first preparing a PEBF/graphene hybrid solution, followed by adding BMI into the solution to produce a ternary material system. Recently, it has been found that carbon materials such as carbon nanotubes, fullerene, and graphene can serve as either a diene material in the [4 + 2] DA cycloaddition with various dienophiles or a dienophile material to react with diene compounds to form DA adducts. Therefore, for the PEBF/graphene hybrid, the furan groups of PEBF could be expected to behave as active diene sites to readily interact with graphene (dienophile) via a DA cycloaddition reaction, resulting in grafting PEBF onto the surface of graphene. For the modified graphene sample, the defect condition and ordered/disordered structures could reveal significant differences from those of the non-modified graphene. Thus, Raman analyses were subsequently performed to study the structural features to confirm the DA reaction between PEBF and graphene. As shown in D/IG value of 0.17 higher than that of the pristine graphene sample, showing the evidence for the successful DA reaction. More importantly, the furan groups of PEBF (diene) and maleimide groups of BMI (dienophile) are highly reactive for DA reaction. Therefore, the diene/dienophile pairs from the furan/maleimide, furan/graphene, and maleimide/graphene combinations could efficiently induce multiple DA reactions, resulting in a DA crosslinked network, wherein graphene sheets were uniformly dispersed in the polymeric matrix. In the current study, different amounts of graphene sheets were added to fabricate a series of hybrid samples. The sample designations and corresponding compositional characteristics of the hybrid system are listed in −1, which correspond to the C=C stretching vibration of BMI and C=C stretching of DA adduct, respectively. The occurrence of these two signals clearly indicated the formation of DA adducts within the PEBF/graphene/BMI hybrid system. Additionally, the pristine PEBF sample exhibited a shoulder peak at 750 cm−1 associated with the signal of furfuryl moiety of the copolymer sample. However, the FTIR spectra of DA-PEBF-5 did not exhibit this shoulder peak, which again proved the formation of DA adducts with the rupture of the original furan rings in PEBF [The Raman analysis data and suspension condition of the PEBF/graphene hybrid indicated the successful incorporation of furan functional groups onto graphene surfaces through DA reaction. Furthermore, BMI was added into the PEBF/graphene hybrid to fabricate a PEBF/graphene/BMI ternary system. For the ternary material system, graphene could also serve as a functionalization agent which provided diene sites to react with maleimide groups of BMI (dienophile). Thus formed DA adduct could be also identified by using Raman analysis. For the BMI/graphene hybrid, its Raman spectrum  exhibite in PEBF .To further understand the dispersion of graphene sheets in the hybrid system, SEM measurements for monitoring the fracture surfaces of the nanocomposites were subsequently carried out. For the DA-PEBF-0 sample, its SEM micrograph a showed We subsequently studied the thermal stability of the PEBF/graphene/BMI hybrids. The TGA thermograms of the composite samples with different amounts of graphene sheets can be seen in To further verify the thermal reversibility of the PEBF/graphene/BMI hybrid system, a sol–gel experiment was used. This investigation was taken with a solid/liquid mixture prepared by mixing DA-PEBF-2 with DMSO solvent (60 wt % in DMSO). Shown in Due to the thermally reversible feature of DA mechanism, the PEBF/graphene/BMI hybrid system was expected to have self-healing ability for repairing structural damages. For evaluating the self-healing performance of this system, a rectangular bulk sample with a cut of 1 mm depth on its surface was first prepared, followed by monitoring the morphological change of the cracked sample under different heating temperatures by using an optical microscopy. These measurements were started from room temperature with a heating step of 10 °C. At each temperature, the measured sample was isothermally heated for 10 min to cause the surface morphology of the sample to reach an equilibrium state. Shown in T is the total EMI shielding effectiveness, SEA is the absorption of electromagnetic wave, SER is the reflection from the material surface and SEM is the multiple reflections occurred at the inhomogeneous interfaces within the material [The EMI shielding performance of the hybrid system was further quantified as the relative intensity ratio between the incident electromagnetic wave to the transmitted wave. The total attenuation of the incident electromagnetic wave can be expressed as the following equation:material ,53. Notematerial . Thus, tT, SEA, and SER in Ku-band are further summarized in T of 14.4 dB. Additionally, the SEA and SER of DA-PEBF-1 are measured to be 0.9 and 13.5 dB. From these results, we could observe that the reflection efficiency mainly provided a major contribution to the attenuation of the incident electromagnetic microwave rather than the absorption efficiency. The reflection of electromagnetic waves could be attributed to the impedance mismatch between air and the hybrid system with uniformly dispersed conductive graphene sheets. As for incorporating 2 wt % graphene into the hybrid (DA-PEBF-2), we could observe that the DA-PEBF-2 sample exhibited a SEA of 1.5 dB, a SER of 14.2 dB, and gave a SET of 15.7 dB higher than that of the DA-PEBF-1 sample. Furthermore, an improvement in the EMI shielding performance was achieved in the DA-PEBF-5 sample, showing a SEA of 4.0 dB, a SER of 12.6 dB, and a SET of 16.6 dB. As a comparison, it could be clearly observed that the SEA value gradually rose with the increasing graphene fraction while the level of SER only showed a tiny variation. The changing trend of EMI shielding performance of the PEBF/graphene/BMI system could be attributed mainly to the different microstructures of the hybrid samples. Based on the SEM results discussed above, there was a structural change from a uniform dispersion of graphene sheets to a continuous graphene distribution as the graphene content was increased from 1 to 5 wt %. The gradually contacted graphene sheets could form interconnected networks in the polymeric matrix and provided the ability to restrict the incident electromagnetic microwaves from escaping from the compartments and caused the waves to be multireflected and absorbed [The variation in total EMI SE in Ku-band (12.4~18 GHz) as a function of different amounts of graphene for the PEBF/graphene/BMI hybrid samples is presented in absorbed , leadingT to at least 94% of the initial value  were cut to form a large crack with a width of 1 mm and depth of 2 mm. From the experimental results, it could be observed that the self-repairability for healing the structural defect simultaneously resulted in a promising restoration of SEshown in c, demonsIn summary, we have successfully synthesized a novel biobased PEBF copolymer and fabricated a PEBF/graphene/BMI hybrid material system by incorporating graphene sheets and BMI into the polymeric matrix. Beside the reactive furan-maleimide combination, graphene could also serve as an effective DA crosslinking agent to build the DA crosslinked network. For this hybrid system, the DA adducts induced from multiple diene/dienophile combinations and their thermal reversibility were systematically analyzed by Raman, TEM, FTIR, SEM, WAXS, TGA, DSC, and sol–gel measurements. This organic/inorganic hybrid system provided multiple functions including self-repairability as well as EM wave shielding ability. Additionally, the use of biobased monomer ethylene brassylate further showed the benefits of economics and environmental friendliness. Therefore, this research provides a new way for developing advanced biobased materials with self-repairing and EMI shielding functionalities, which could be applied as self-healing protection layers for EMI shielding applications.


Over the past decade, major discoveries in retrotransposon biology have depicted the neural genome as a dynamic structure during life. In particular, the retrotransposon LINE-1 (L1) has been shown to be transcribed and mobilized in the brain. Retrotransposition in the developing brain, as well as during adult neurogenesis, provides a milieu in which neural diversity can arise. Dysregulation of retrotransposon activity may also contribute to neurological disease. Here, we review recent reports of retrotransposon activity in the brain, and discuss the temporal nature of retrotransposition and its regulation in neural cells in response to stimuli. We also put forward hypotheses regarding the significance of retrotransposons for brain development and neurological function, and consider the potential implications of this phenomenon for neuropsychiatric and neurodegenerative conditions. Neural cell diversity underpins this complexity, and has classically been defined in terms of the morphological differences between cell types, their diverse connectivity patterns, physiological and functional properties and the expression of various transcription factors (TFs), cell surface and secreted molecules ,2. At thSomatic mosaicism is defined as the existence of two or more cells with different genotypes within one individual. Depending on its developmental timing, mosaicism can encompass mutations that are heritable (germline mosaicism), non-heritable (somatic mosaicism) or a combination of these two outcomes ,11–14. R2.in cis, L1 can mobilize in trans non-autonomous short interspersed element (SINE) retrotransposons. These include 7SL-derived Alu elements, composite SVA (SINE–variable number tandem repeat–Alu) elements, and cellular mRNAs, resulting in processed pseudogenes [Alu copies are approximately 300 bp in size and represent the most abundant transposable element by copy number (approx. 11% by sequence) [Alu, and comprise only about 0.2% of the genome sequence [a).Retrotransposons are the main class of transposable elements found in most mammalian genomes. Based on the presence of long terminal repeats (LTR) in their structure, they are classified into LTR and non-LTR retrotransposons. The LTR group consists of ERVs (endogenous retroviruses), which comprise approximately 8% of the human genome and represent remnant retrovirus sequences incorporated into the host germline after ancient viral infections ,20. The udogenes –25. L1 cudogenes . Alu copequence) ,26,27. Ssequence ,28–30  L1s [in vitro to date belong to the L1-Ta and L1-preTa families [Alu subfamilies, such as AluYa5 and AluYb8 [Owing to truncation, deletion, internal rearrangement and other mutations, the vast majority of human retrotransposon sequences are incapable of further mobilization and are considered molecular fossils . Computaive) L1s . All of families –42. Simid AluYb8 , and SVAd AluYb8 ,24,29 had AluYb8 . However3.cis-preference [b) [All retrotransposons mobilize via a replication mechanism involving an RNA intermediate . During eference , meaningeference ,49 or eneference  makes a eference   ,50,51.Retrotransposition does not always result in the faithful duplication of an element, particularly in the case of L1. Owing to errors during reverse transcription, only approximately 40% of L1 copies are identical to their source, or donor, L1 . Also, 5As a result of 5' truncations, internal inversions or deletions  and poin4.Although nearly 70 years have passed since Barbara McClintock's seminal studies of transposable elements in maize ,62, ongoEGFP gene is interrupted by an intron in the same transcriptional orientation as the L1. Thus, only cells with successful L1 retrotransposition events can express GFP because the EGFP intron is removed from the RNA intermediate, followed by reverse transcription and integration into a genomic location. When the L1-EGFP system is employed in neuronal cultures, GFP co-localizes with neuronal markers Map2 and β-tubulin, whereas very little to no GFP co-localizes with astrocyte or oligodendrocyte markers [Over the past decade, three main tools have facilitated the discovery and study of L1 retrotransposition in the brain. Firstly, an engineered L1 reporter construct, previously developed to recapitulate L1 retrotransposition in cultured cells ,70, has  markers . Neurons markers –74. Alth markers , the deset al. [Secondly, to estimate the number of L1 copies across different tissues and brain areas, Coufal et al.  developeet al. ,74,76. Tet al. , this aset al. . New quaet al. ,79.Thirdly, high-throughput DNA sequencing strategies have been developed to detect, quantify and resolve L1 insertions. Whole-genome sequencing (WGS) or targeted sequencing of retrotransposon–genome junctions has been applied to bulk brain, pooled neurons and whole-genome amplified (WGA) material from single neuronal nuclei from post-mortem human brain –7,10,80.Providing a valuable orthogonal approach to single-cell genomic analysis, a recent study used somatic cell nuclear transfer to reprogramme postmitotic olfactory bulb neurons into enucleated oocytes and cloned the neuronal genome to produce enough DNA for WGS without the need for WGA. WGS analysis of the resulting clones revealed several de novo L1 insertions . These s5.a). Neural diversity arises during early embryogenesis through the spatial and temporal patterning of neuroblasts and neuronal progenitor cells. A complex network of gene expression determines a particular cell type-specific progenitor domain and fate [b).Retrotransposition in the brain could occur at any stage of life, from early brain development to brain maintenance and decline during adulthood, and also influence neural diversity and survival a. Neuraland fate . Expressand fate . Althougand fate ,87. An eand fate . Whether5.1.et al. [in vitro, in rodent primary hippocampus-derived NPC cultures, and in vivo, in transgenic mice. L1 expression in transgenic mice was observed as early as embryonic day (E) 12.5, when the first waves of immature differentiated neurons appear in the brain [et al. [Over a decade ago, Muotri et al.  presentehe brain . These d [et al.  in a stu [et al. , the cel [et al. –92. The Another explanation for L1 activity in proliferating NPCs may be a more relaxed chromatin state. A relaxed chromatin state is correlated with pluripotency and proliferation, and differentiated cells have more condensed chromatin than progenitor cells . Open chFinally, TFs can stimulate L1 to retrotranspose during neuronal differentiation. Sex determining region Y-box 2 (SOX2), which is expressed in stem cells and neural progenitors, and is essential in maintaining a proliferative state, can bind to the 5' UTR of L1 and repress promoter activity . During 5.2.et al. [et al. [et al. compared the retrotransposition of a hybrid adenoviral L1-EGFP vector in dividing versus non-dividing neural cells by infecting NPC cultures with the L1 reporter and concomitantly adding 5'-bromo-2'-deoxyuridine (BrdU), which labels dividing cells. Immunostainings of differentiated NPC cultures infected with L1-EGFP at 31 days post-NPC differentiation showed the presence of neurons expressing only EGFP but not the cycling marker, BrdU. When comparing the number of integrated L1-EGFP copies in cultures infected with the L1 reporter at day 0 (multi-potent NPC) versus day 31 of differentiation (in mature neurons), a sixfold increase in L1-EGFP copies was observed by qPCR against the EGFP splice junction in mature neurons, even when correcting for differences in proliferation rate [in vitro assay to compare dividing versus non-dividing neural cells. Going forward, it will be interesting to address this question in vivo, perhaps by using an inducible knock-in reporter model. Furthermore, it would be very interesting to explore in detail the mechanisms through which retrotransposons escape epigenetic silencing and mobilize in postmitotic neurons.If we accept that endogenous L1 mobilization can occur during adult neurogenesis, can it also occur in postmitotic neurons? This is a fundamental question because the lifespan of mature neurons can be as long as a human lifespan, and therefore, any potential for somatic retrotransposition in this context may lead to the largest absolute accumulation of new L1 insertions found in the brain. Crucially, Kubo et al.  showed i [et al.  confirmeion rate . This wa6.It is not established whether retrotransposition in the neural genome is part of normal brain function. It is however plausible that, if retrotransposons did contribute to normal brain function, it would be via altered splicing and DNA methylation of genes, with these being routes to perturb the transcriptional output of cells. For example, pseudogene transcripts can carry microRNA (miRNA) recognition sites and facilitate degradation of their target miRNAs, acting as competitive miRNA targets to the miRNA targets of their parent genes . Such ps7.PDHX gene encoding pyruvate dehydrogenase, which results in pyruvate dehydrogenase deficiency, a neurodegenerative disorder [Retrotransposon insertions can significantly alter protein-coding and regulatory regions of the genome, and thereby affect gene expression and other cellular outputs ,99–103. disorder . Genomicdisorder . Recombidisorder . Transcrdisorder . An antidisorder ,114–116,Glyrβ) gene which leads to aberrant splicing of the pre-mRNA by exon skipping, thus resulting in reduced intact subunit β expression in the brain [Reln) gene, which also leads to exon skipping and a frame shift, in this case generating a 220 bp deletion of the Reln mRNA, and leading to inefficient secretion of Reln truncated protein [Reln mutant mice recapitulate the phenotype seen in patients with lissencephaly caused by other Reln mutations [New L1 insertions can lead to aberrant transcriptional splicing –121. Twohe brain ,119. As  protein ,122,123.utations . Hence, 8.8.1.in vitro when tagged with a fluorescent or selectable marker [et al. [Retrotransposition depends on a mobile element's intrinsic ability to ‘jump’, and its host cell's capacity to defeat this mobilization. Despite their significant presence in the genome, almost all human L1 copies are 5' truncated, or contain internal mutations and rearrangements, and are not able to mobilize. A few L1 copies are full length, remain transcriptionally active and have intact ORFs and therefore have the capacity to act as source, or donor, elements in a cycle of retrotransposition. An even smaller subset  retrotranspose efficiently e marker ,70 and ae marker ,42, althe marker . If a ce [et al.  recently [et al.  identifi8.2.As retrotransposition events can cause such large effects on gene expression, cell function and ultimately organism fitness, several mechanisms exist to limit and regulate L1 mobilization in germ and neural cells. These mechanisms have been reviewed comprehensively ,127. We Several epigenetic factors are known to repress L1. For example, methyl-CpG-binding protein 2 (MeCP2) is present ubiquitously in the body and in higher abundance in mature neurons. MeCP2 binds 5-methyl-cytosine residues in CpG dinucleotides and interacts with histone deacetylase protein (HDAC) and transcriptional SIN3A corepressor complexes to repress transcription –134. MeC. As new L1 insertions carry TF binding sites and potentially attract epigenetic suppression [In addition to epigenetic regulation, retrotransposon activity can be regulated by specific TFs, such as yin yang 1 (YY1), runt-related transcription factor 3 (RUNX3), SOX2 and tumour protein p53 (p53). YY1 is a zinc finger protein expressed ubiquitously in the brain. It is critical for regional patterning of the brain and neuronal differentiation, as it regulates genes including Otx2 and Engrailed 2 –141. YY1pression , the intpression ,154, andpression . Host fapression , or DNA pression . Hence, 8.3.et al. [et al. [in vivo.Numerous studies have proposed that environmental factors may trigger hyperactivation of L1 and other retrotransposons. However, most of these studies are preliminary and the experiments have been largely performed on cell lines. For instance, heavy metals such as mercury, nickel and cadmium seem to increase L1 retrotransposition in HeLa and neuroblastoma cells –159, andet al.  describe [et al.  reported [et al. ,163,165.9.Alu data. The implication of HERVs in neurological disease, such as multiple sclerosis, schizophrenia and bipolar disorder, has been recently reviewed [Retrotransposition in the early embryo and committed germline can result in heritable mutations that cause genetic disease ,63. Severeviewed ,209,210.reviewed ,212. Pro9.1.MeCP2 gene [MeCP2 mutant rat NSC cultures and transgenic mice [MeCP2 mutation.A prominent example of a neurodevelopmental disorder that has been linked to retrotransposon activity is Rett syndrome (RTT). RTT is a progressive, severe neurodevelopmental disease associated with a mutation in the CP2 gene . MeCP2 gCP2 gene ,135. MicCP2 gene . Increasnic mice . Elevatenic mice . Howeveret al. [Psychiatric diseases, such as autism, schizophrenia and bipolar disorder, have also been linked with retrotransposon activity ,190–192.et al.  sought tet al. . WGS peret al. . The autet al. [et al. [Increased retrotransposon copy number and mRNA levels have been reported in schizophrenia and depression ,192. Bunet al.  revealedet al. . A consiet al. . WGS peret al. . Howeveret al. . Very re [et al.  proposed [et al. . As a qPAlu epigenetic regulation has been reported in post-traumatic stress disorder (PTSD), an anxiety condition characterized by persistent re-experiences of a past traumatic event or events [Alu in serum when compared with healthy individuals [Even if elevated somatic retrotransposition ultimately is not found to occur in a given neurological condition, a molecular signature of L1 regulatory disruption may indicate a wider landscape of epigenome abnormality, and prove useful as a diagnostic tool. For example, altered L1 and r events . PTSD paividuals . Non-PTSividuals . These f9.2.ATM gene encoding a serine/threonine kinase [ATM mutation in cultured human NPCs and ATM knockout in L1-EGFP mice significantly increased L1-EGFP retrotransposition, measured by the number of GFP-positive cells, without affecting L1 promoter activity or endogenous ORF1p levels, and with no change in cell division rates or survival [ATM mutant cells [in vivo, is required to corroborate these results, and identify the role of ATM in controlling L1 integration.Neurodegenerative conditions, such as Parkinson's disease, Huntington's disease and Alzheimer's disease, represent a group of nervous system disorders characterized by the selective death of neuronal subsets in particular brain regions . Experime kinase , which le kinase . ATM rese kinase . ATM mutsurvival . Notablynt cells , potentiDrosophila brains, recapitulated these results from patients and mouse models, demonstrating that TDP-43 dysfunction results in de-repression of retrotransposons [gypsy ERV transcript levels as previously reported to be elevated in ageing flies [gypsy ameliorated this phenotype, suggesting that gypsy may be involved in cell death, potentially by mediating DNA damage [As many neurodegenerative conditions are associated with ageing, retrotransposition in neurodegenerative conditions may, in general, reflect conditions encountered in senescent cells. Accumulation of oxidative DNA damage and unrepaired DNA, as well as changes in methylation patterns commonly associated with ageing, might lead to reduced silencing of retrotransposition in the brain. As an example of this, TAR DNA-binding protein 43 (TDP-43) is a nucleic acid binding protein involved in transcriptional repression and RNA metabolism during stress response. Mutant TDP-43 is usually associated with neurodegenerative disorders, but it can also be present in healthy elderly people . Accumulnsposons . Interesng flies . Human TA damage .et al. [Alu within and adjacent to mitochondrial genes [Alu retrotransposon insertions in a number of translocase of outer mitochondrial membrane genes [Alu insertions in two genes involved in mitochondria stabilization and function led to disorders with a neurodegenerative component [Alu activity can preferentially insert into and induce mitochondrial gene disruption.Many neurodegenerative disorders are strongly linked with mitochondrial dysfunction. In intriguing recent work, Larsen et al.  put forwal genes . Previoune genes ,230,231.omponent ,194. Mor10.in vivo, and the regulatory mechanisms involved in allowing L1 retrotransposition in mature neurons require further investigation. Environmental stress, as well as genetic dysfunction in L1 silencing factors, can result in high retrotransposition levels, and possibly lead to neurological disease. This also requires extensive investigation, as we lack even basic understanding of the pathways on which stress factors or dysfunction in silencing factors can act to impact retrotransposition in neural cells. Our understanding of retrotransposition in the brain is still very much in its infancy.It is now well established that retrotransposon-driven mosaicism can occur in the mammalian brain. Dynamism in TF activity, and that of other regulatory mechanisms described to act during embryonic and adult neurogenesis, provides a temporal and spatial niche amenable to retrotransposition. Additionally, retrotransposition may not be limited to NPCs; it may also take place in postmitotic neurons. Further proof is required to be certain that this can occur Further advances in single-cell genomics  to unde