Terahertz modulators with high tunability of both intensity and phase are essential for effective control of electromagnetic properties. Due to the underlying physics behind existing approaches there is still a lack of broadband devices able to achieve deep modulation. Here, we demonstrate the effect of tunable Brewster angle controlled by graphene, and develop a highly-tunable solid-state graphene/quartz modulator based on this mechanism. The Brewster angle of the device can be tuned by varying the conductivity of the graphene through an electrical gate. In this way, we achieve near perfect intensity modulation with spectrally flat modulation depth of 99.3 to 99.9 percent and phase tunability of up to 140 degree in the frequency range from 0.5 to 1.6 THz. Different from using electromagnetic resonance effects , this principle ensures that our device can operate in ultra-broadband. Thus it is an effective principle for terahertz modulation. Low-dimensional materials show promise for applications in imaging, spectroscopy and ultra-broadband communications. Here, the authors report an effect of Brewster angle control at graphene-quartz interface for applications in terahertz modulation over a broadband range from 0.5 to 1.6 THz. These applications drive the need for THz modulators with high modulation depth, broad operation bandwidth, and high modulation speed5. Manipulating THz light to achieve both high modulation depth and broadband response in a device is a great challenge. One major limitation of the state-of-the-art THz modulator is the narrow bandwidth; current technologies rely primarily on narrow band resonance effects13  for enhancing the interaction between the THz wave and the tunable conductivity materials. Semiconductor hybrid structures are developed, but these architectures require the assistance of high-power optical pumping. Another issue is the low modulation speed of the non-solid-state devices, such as the modulators based on ion-gel gate or liquid crystal.Terahertz technology shows promise for many applications including imaging, spectroscopy, and communications19. It has attracted great attention in the THz region because of its tunable conductivity, typically from comparatively high-resistance state to semi-metal state23. The first graphene THz modulator is demonstrated by Sensale-Rodriguez et al.24 with an ultra-broad operation band and a modulation depth of 15% using monolayer graphene. To improve the modulation depth, complex optical resonance structures 25–27, semiconductor hybridization29, and ion gel31, are assembled to work together. However, these structures could not overcome the above-mentioned problems. Therefore, there is still a lack of an effective fundamental approach to achieving a broadband device with deep and wideband modulation range.Graphene is an ideal material for photoelectronic devices due to its unique propertiesp-polarization light experiences zero reflection when it is incident to a medium at the Brewster angle and a π-phase shift occurs to the reflected light when the incident angle jumps across the Brewster angle. Furthermore, the Brewster angle can be tuned by varying the surface conductivity of the medium33. Based on this fundamental principle, we experimentally employ an atomic layer of graphene to tune the surface conductivity and demonstrate that the Brewster angle of a graphene–quartz device can be tuned from 65 to 71° by varying the conductivity of graphene. By properly selecting the incident angle, the device can work as a THz-intensity modulator with spectrally flat modulation depth of 99.3–99.9% in a wide range from 0.5 to 1.6 THz, and operate as a phase modulator with tunability higher than 140°. Compared to the high-performance THz modulators based on light-trapping effects, this principle ensures that the device can operate as an ultra-broadband spectrally flat terahertz modulator. Actually, the reported bandwidth in this work is mainly limited by the effective bandwidth of the THz system. An even broader bandwidth can be theoretically extrapolated from the operation principle. Our device presents a THz modulation based on a graphene-controlled Brewster angle device and achieves record performance at room temperature.Here, as a proof of concept, we demonstrate a solid-state modulator with near-perfect tunability, ultra-broad operation bandwidth, and fast modulation speed based on tunable Brewster reflection at graphene/quartz surface. It is well known that σg is placed on the dielectric silica substrate. Light with p-polarization is incident from air onto the graphene/silica medium. According to Maxwell’s equations, together with the boundary conditions . The insertion loss of this device, We first present the simulation results based on the physical model in Fig. ero Fig.  and the ero Fig. , which imentclass2pt{minim2O3/TiOx sandwich structure is constructed for a solid-state electrical gate to tune the conductivity of graphene (details of the fabrication can be seen in the Methods section). A 50-nm Al2O3 layer is used as a dielectric gate, which has a negligible effect on the light reflection. The back gate electrode is made of 10-nm thickness of a TiOx (sheet resistance ~2000 Ω) film. This thin and high-resistance film ensures the transparency for the THz light. The transparency of TiOx is verified by THz transmission spectrum and the loss of TiOx is also discussed in Supplementary Figure The real device in this work is schematically shown in Fig. 35. However, these methods are hard to active tuning of Brewster angle. To change the Brewster angle, the unit structure or periodic parameter for the metamaterial or metasurface should be changed. Besides, Brewster angle of metamaterials/metasurface is always frequency-dependent, due to their resonance nature. As far as we know, this work is the first time to realize an active tunable Brewster angle and achieve broadband response.In order to obtain the Brewster angle of the device, we measured the reflected THz pulse with an incident angle of 55–75°, as well as gate voltage from −12 to 12 V. Three typically reflected THz pulses in the time domain are shown in Fig. 38–40. This experimental insertion loss is mainly due to the poor quality of commercial graphene and the fabrication process.From the result in Fig. In order to further clarify this phenomenon, we simulated the electric field distribution at the frequency of 0.8 THz, when graphene’s conductivity is 0.5 and 3.5 mS, corresponding to the gate voltage of 14 and −12 V in the experiment. As shown in Fig. 62341–43. More importantly, owing to the solid-state-based modulations, our device provides a high modulation speed, as shown in Fig. x. Here, we take a resistance of 250 Ω for the graphene and 1000 Ω for the TiOx, which are calculated by the half of averaged square resistance over the gate voltage range. A capacitance (C) of ~140 nF is calculated by adopting a 50-nm Al2O3 and an active device (graphene) area of 1.0 × 1.0 cm. Therefore, the calculated RC time constant is 1.75 × 10–4 S, corresponding to a modulation speed of ~6 kHz, which agrees well with the experimental result. Higher modulation speed (shorter RC time constant) can be realized through replacing TiOx by a higher-conductivity material  and reducing the device size. For instance, by utilizing graphene to replace TiOx and reducing the device size to ~1.0 × 1.0 mm (about two times the wavelength of 0.8 THz), the modulation speed will be ~2.4 MHz, which is comparable with other solid-state THz modulators in previous reports27.The performance of the device, both of the modulation depth and operation band, is much higher than that of previous resultsVg = 16 V to Vg = −12 V, as shown in Fig. According to the physical model, a broadband phase modulation with a deep modulation range can be achieved by utilizing the phase-jump property across the Brewster angle. Here, we chose the incident angle of 68° to discuss this issue. The reflected THz time-domain signal changes from an asymmetry “W” shape at the gate voltages of 16 V to an asymmetry “M” shape at the gate voltages of –12 V, which indicates that there should be a large phase shift from 2O3/TiOx sandwich structure on a quartz substrate. The conductivity of the graphene can be electrically controlled to generate a variable Brewster angle. Based on this device, an ultra-broadband THz-intensity modulator with a modulation depth larger than 99.3% and an ultra-broadband-phase modulator with a tunability higher than 140° are demonstrated. Our work presents graphene-controlled Brewster angle device for ultra-broadband THz intensity and phase modulation at room temperature. The promising performance of our device also suggests that there exists a great potential to use graphene in deliberate architecture for active THz devices.In this work, THz modulation-based graphene-controlled Brewster angle device is experimentally demonstrated for the first time. The device is fabricated using a graphene/Alx through annealing at 150 °C. After oxidization, the conductivity of this film was about a reciprocal of sheet resistance of 2000 Ω, which was measured using a four-probe method. Then, a layer of Al2O3 (50 nm) was deposited by atomic layer deposition onto TiOx as a dielectric gate. Afterward, graphene (~1 × 1 cm) was transferred onto the as-prepared quartz/TiOx/Al2O3 substrate. Subsequently, two electrodes (Cr/Au) were fabricated by thermal deposition. One was on graphene and the other one was on TiOx for the gate voltage. The device is schematically shown in Fig. A Ti film of 8 nm was deposited on a quartz substrate (diameter of 2 cm) for the bottom-gate electrode. In order to avoid further reducing the conductivity of Ti, the Ti film was oxidized into TiOA THz-TDS system from Menlo Systems (TERA-K15) was used for the terahertz reflection measurements. A reflection guide was used for manual adjustment of the reflection angle, ranging from a minimal reflection angle of 55 to 75°.Supplementary InformationPeer Review File


Umingmakstrongylus pallikuukensis and Varestrongylus eleguneniensis are two potentially pathogenic lungworms of caribou and muskoxen in the Canadian Arctic. These parasites are currently undergoing northward range expansion at differential rates. It is hypothesized that their invasion and spread to the Canadian Arctic Archipelago are in part driven by climate warming. However, very little is known regarding their physiological ecology, limiting our ability to parameterize ecological models to test these hypotheses and make meaningful predictions. In this study, the developmental parameters of V. eleguneniensis inside a gastropod intermediate host were determined and freezing survival of U. pallikuukensis and V. eleguneniensis were compared.Deroceras laeve, were collected from their natural habitat and experimentally infected with first-stage larvae (L1) of V. eleguneniensis. Development of L1 to third-stage larvae (L3) in D. laeve was studied at constant temperature treatments from 8.5 to 24 °C. To determine freezing survival, freshly collected L1 of both parasite species were held in water at subzero temperatures from -10 to -80 °C, and the number of L1 surviving were counted at 2, 7, 30, 90 and 180 days.Slug intermediate hosts, 0) below which the larvae of V. eleguneniensis did not develop into L3 was 9.54 °C and the degree-days required for development (DD) was 171.25. Both U. pallikuukensis and V. eleguneniensis showed remarkable freeze tolerance: more than 80% of L1 survived across all temperatures and durations. Larval survival decreased with freezing duration but did not differ between the two species.The lower threshold temperature (TU. pallikuukensis and V. eleguneniensis have high freezing survival that allows them to survive severe Arctic winters. The higher T0 and DD of V. eleguneniensis compared to U. pallikuukensis may contribute to the comparatively slower range expansion of the former. Our study advances knowledge of Arctic parasitology and provides ecological and physiological data that can be useful for parameterizing ecological models.Both  The extreme climate of the Arctic makes it one of the most challenging environments for living organisms. Winter temperatures can drop to -50 °C in many parts of the Arctic, and sub-zero temperatures last for nearly two-thirds of the year. The summers are short, cool, and dry, providing a narrow developmental window for ectotherms, including parasites, and a short growing season for endotherms and plants –3. DespiIn the animal kingdom, nematodes are considered the most diverse and successful organisms for their ability to adapt to diverse habitats and survive extreme environmental conditions , 10. NemUmingmakstrongylus pallikuukensis Hoberg, Polley, Gunn & Nishi, 1995 and Varestrongylus eleguneniensis Verocai, Kutz, Simard & Hoberg, 2014, are parasites of Arctic ungulates in areas of the Canadian Arctic mainland and Victoria Island in the Arctic Archipelago [Umingmakstrongylus pallikuukensis is a host specialist and only infects muskoxen (Ovibos moschatus) [V. eleguneniensis is a multi-host parasite that infects muskoxen, caribou (Rangifer tarandus) and moose  [0; lower threshold temperature), larval development inside the intermediate host is minimal, and development to L3 does not take place [0, L1 develop to L3 after accumulating a certain amount of heat, quantified as development degree-days (DD) [Two lung nematodes, hipelago . Umingmaschatus) , 23, whes alces) , 24. Theke place , 26. Aboays (DD) . The L3 ays (DD) . The L3 ays (DD) . The devays (DD) . HoweverUmingmakstrongylus pallikuukensis and V. eleguneniensis co-occur in muskoxen of the western Canadian Arctic and, until recently, were limited to the North American mainland and had not been found in the Arctic Archipelago. However, in 2008, U. pallikuukensis, and in 2010, V. eleguneniensis, were reported for the first time on southern Victoria Island, Nunavut, Canada [U. pallikuukensis establishing at higher latitudes prior to V. eleguneniensis ., Canada  Fig. 1)Umingmaks, Canada , 19. SinU. pallikuukensis in its intermediate host, but similar information for V. eleguneniensis is lacking. Few previous studies have investigated the freezing survival of L1 of protostrongylids [One hypothesis for the differential range expansion of the two parasites is different species-specific thermal requirements and tolerances for the development and survival of their larval stages. Indeed, understanding the developmental responses to temperature in intermediate hosts and freeze tolerance of L1 in the environment is vital for understanding the ecology and transmission dynamics of protostrongylids in general. Kutz et al.  studied ongylids –32, and V. eleguneniensis and U. pallikuukensis. Specifically, we investigated the temperature-dependent development of V. eleguneniensis in a gastropod intermediate host, the meadow slug Deroceras laeve , and compared the freezing survival of L1 of U. pallikuukensis and V. eleguneniensis. This study is essential to our understanding of the thermal ecology of these two emerging parasites in the Canadian Arctic. The resulting data on thermal tolerances provide essential parameter estimates for parasite distribution and transmission models [The objectives of this study were to determine the temperature requirements and tolerances of n models  and willU. pallikuukensis and V. eleguneniensis. First, temperature-dependent development of V. eleguneniensis in D. laeve was determined following the methodology used for U. pallikuukensis by Kutz et al. [Two sets of experiments were carried out to determine the impact of temperature on development and survival of z et al. . SecondlD. laeve, were collected from their natural habitat near Sheep River Provincial Park  and Sundre , Alberta, Canada. Refuge traps comprised of dampened cardboard, masonite board, and fabric mats, often baited with grape juice, were used for collecting slugs near creeks and wetlands [V. eleguneniensis were isolated from the feces obtained from wild muskoxen in northern Quebec  using the modified beaker Baermann technique [V. eleguneniensis L1 [The gastropod intermediate hosts, wetlands , 35. Thewetlands  and tranwetlands  at 8 ± 2echnique . The fecensis L1 , 38. Theensis L1  and PCR.The experimental infection was performed as previously described by Hobert et al.  and KutzV. eleguneniensis [For each trial, three slugs were haphazardly selected at designated days post infection and digested in a pepsin hydrochloride solution , 25. Theeniensis , and knoeniensis , 38. Theeniensis . After dVarestrongylus eleguneniensis L1 were obtained from the fresh feces of a captive muskox that was experimentally infected with the larvae obtained from wild muskoxen from northern Quebec . Umingmakstrongylus pallikuukensis L1 were obtained from fresh fecal samples collected from wild muskoxen near Norman Wells, Northwest Territories . Within 24 h of collection, fecal samples were transported to the lab in whirl packs  maintained at 4 ± 1 °C (temperature monitored by LogTag® temperature recorder) and stored at 4 ± 1.5 °C until processed. For both parasite species, L1 were extracted using the Baermann method [n method  within on method , 39.U. pallikuukensis and V. eleguneniensis was studied under four  and three  sub-zero temperatures, respectively , and degree-days for development (DD), were estimated by fitting the daily development rate D is the number of days from infection to the first appearance of intermediate third-stage larvae (iL3) and T is temperature. The parameters were estimated by linear regression of development rate (1/D) over temperature (T), where slope equals 1/DD and the intercept equals T0/DD [0, and (iii) we wanted to compare to other protostrongylids, especially with lungworm U. pallikuukensis, and linear models were used to derive the parameters for these protostrongylids.All analyses were conducted using R statistical software . The thels T0/DD , 42. We U. pallikuukensis and V. eleguneniensis. The response was the proportion of individuals in each well surviving until inspection at 2, 7, 30, 90 or 180 days freezing duration, calculated as the surviving L1s divided by the initial number of viable parasites in each well. Fixed effects included parasite species, temperature, freezing duration, and the interaction between temperature and species, representing the differential effect of freezing temperature on the two species. The plate was initially included as a random effect, but the variance among the plates was small, and the inclusion of the random effect did not change the parameter estimates for the fixed effects, so the effect of the plates was ignored. Ten different models were fitted representing different combinations of the four fixed effects. The models were compared using Akaike Information Criterion (AIC). There was a high degree of model and parameter uncertainty, and so we report the model-averaged predictions for survival over the top five models which comprised more than 90% of the cumulative Akaike weight [Binomial generalized linear models  were fitted to investigate the effect of temperature and freezing duration on the survival of e weight , using te weight .Varestrongylus eleguneniensis larvae successfully developed from L1 to L3 at temperatures between 12.5 to 24 °C  = 1297, P < 0.0001), with R2 of 0.99. From equation 0 = 9.54 °C  and 74 dpi (two slugs). Emergence from all four slugs continued to day 83, and although no emergence was detected on subsequent observations, L3 were found inside all of the slugs on digestion after they died at days 85 and 87, respectively.U. pallikuukensis and V. eleguneniensis had high freezing survival at all temperatures and all durations  for V. eleguneniensis.L1 of both ons Fig. . There wons Fig. . Temperaons Fig. . Survivaons Fig. . Despiteons Fig. , within ons Fig. , suggestlar Fig. . The modV. eleguneniensis inside the intermediate host, D. laeve, was positively related to temperature, and the lower threshold temperature (T0) and the thermal constant required for development into infective stage (DD) were within the range determined for other northern protostrongylids  at -80 °C, frozen for a similar time. Developmental thresholds and freezing survival of more temperate species seem to be comparatively lower. For example: Muellerius capillaris, a temperate protostrongylid, has a considerably lower T0 (4.2 °C) and is less tolerant to freezing despite being relatively closely phylogenetically related to U. pallikuukensis [Parelaphostrongylus tenuis, another temperate species, also has a lower freezing tolerance than it northern counterparts - approximately 70% survival of L1 when frozen in feces at -15 to -20 °C for 182 days [P. tenuis L1 survive a constant temperature of -14 °C in the lab when frozen in fecal pellets for four months. The variation in developmental and survival parameters among protostrongylid species is most likely a result of biological differences between both parasite and host species that are shaped by various ecological and evolutionary processes [0 for northern protostrongylids is an ecological adaptation to the Arctic conditions  [0 ensures that L1 enter the developmental phase only when the temperature is consistently warm, thereby increasing the chances of successful development to L3 in a single season. This further prevents mortality of developing larvae  and the intermediate hosts themselves over the winter [The developmental parameters and freeze tolerance capabilities among protostrongylids with Arctic and sub-Arctic distributions are quite comparable - developmental thresholds lie around Tfreezing –32. Withte hosts , 48. Basangiferi . The litangiferi  reportedalvorsen  did not uukensis . Parelap182 days  found throcesses . For ins period) . Higher e winter .U. pallikuukensis and V. eleguneniensis warrants further explorations on mechanisms of freeze resistance. For other nematodes, several biochemical and physiological mechanisms to survive freezing have been identified [U. pallikuukensis and V. eleguneniensis L1, but because the survival was very high in water, they may employ a freeze-tolerance strategy and survive inoculative freezing, as described for other nematodes [The extreme freeze tolerance of entified , 52–54. entified , 55, 56.entified . We do nematodes , 58.The Arctic continues to warm at an unprecedented rate, driving the emergence and spread of pathogens , 59, 60


The LC wireless passive humidity sensor was optimized by performing HFSS simulations and fabricated via a screen-printing technique. The MoS2 nanoflakes were characterized by laser scanning confocal microcopy, scanning electron microscope, and X-ray diffraction. The measurements show the sensor can operate stably for a long time with a hysteresis of 4% RH (relative humidity) in 10–95% RH. At low humidity environment (10–60% RH), the sensitivity of the as-prepared humidity sensor is 2.79 kHz/% RH, and a sensitivity of 76.04 kHz/% RH was realized in a high humidity environment (60–95% RH). In this regard, the sensing mechanism was discussed in the scope of proton transfer theory. The test results also indicate that the response time and recovery time of the prepared sensor are 10 s, 15 s, respectively and between 15~40 °C the sensitivity of sensor was not temperature-dependent in the range of 10~80% RH. In addition, the sensor shows less sensitivity to temperature in the 15–25 °C range at 90% RH. All of these experimental results show that the prepared LC wireless passive humidity sensor can stably monitor the rapidly changing humidity in a sealed and narrow environment for a long time.In this study, an LC wireless passive humidity sensor based on MoS Humidity sensors have been widely used in industrial, agricultural, medical, food package and household life ,2,3,4,5.2 have been widely studied and demonstrated their gas sensing capability [2 being as a gas sensing material is gaining more attention due to the unique properties including tunable ban gap, lower intrinsic background carrier density, etc. Moreover, owing to the special molecular structure, there exist many dangling bonds on the edge of the MoS2 structure and these provide a large amount active sites interacting with gas molecules, which implies MoS2 is a promising material for humidity sensing [2 have not been reported.Owing to the high surface area to volume ratio, 2D materials such as graphene, MoSpability ,28. Howepability . On the  sensing . Neverth2 nanoflakes. With the help of High Frequency Structure Simulator (HFSS) software, the structure and distance–S11 curve of the as-designed humidity sensor was optimized, and the sensor circuit was fixed to the alumina substrate by screen printing technology which is simple to operate and low cost. By dint of laser scanning confocal microcopy (LSCM) we investigated the morphology and topography of the as–sprayed MoS2 film and MoS2 nanoflakes were characterized by a scanning electron microscope (SEM) and X-ray diffraction (XRD). Then the experimental and simulation results were compared and the prepared sensor was tested over a wide humidity range at room temperature. Moreover, other sensing performances such as hysteresis, the response and recovery time of as-prepared humidity sensor were investigated.In this work, we studied a LC wireless passive humidity based on MoSsL, and variable sC, resonates based on Equation (1):The principle circuit of the designed LC wireless passive sensor is shown in f, which is the resonant frequency (RP) of the sensor resonant circuit, is uniquely determined by the variable C. The structure of the proposed humidity sensor is shown as 2 nanoflakes as humidity sensing film. Here, the capacitance of the MoS2-covered interdigital electrode is calculated using Equation (2) as follows:N is the number of interdigitated electrodes, l, g, h are the length, width, thickness of a interdigitated electrodes, and ε, which changes as the MoS2 nanoflakes absorbs or desorbs the moisture in ambient environment, is the relative dielectric permittivity of the MoS2-moisture mixture. cD and outD are the width and the length of inductance. As the capacitance the humidity sensor circuit resonates, the sweep source connecting with an antenna such as network analyzer with a certain frequency range can detect the resonance frequency of humidity sensor circuit, thereby realizing wireless measurement of humidity parameter.Therefore, −3 and 3960 kg/m2, while the bulk conductivity and mass density of the Ag conductor was 6.1 × 107 Siemens/m and 10,500 kg/m2. The dielectric constant of MoS2 was set to be 12.33. In the analysis, we primarily probed the S11 values of sensor in the coupling distance range of 0–30 mm with the increment of 5 mm, and the derived results shown in 11 value decreases as distance increases in 0–10 mm, and then dramatically creeps with increasing distances in 10–25 mm. The S11 value at the distance of 10 mm was higher than at any other distances and its value is up to −12.77 dB which indicates a robust signal level at this position. In this regard, we assume the preferable coupling distance between humidity sensor and antenna was 10 mm owing to the high S11 value. Further, the electric field distribution of the sensor at the distance of 10 mm is shown in 11-f resonance curve of as-designed humidity sensor at 10 mm is shown in 11 value is up to −12.77 dB.Then, the proposed humidity sensor structure was optimized by High Frequency Structure Simulator (HFSS) software. 2 humidity sensor using screen printing technology which has the advantages of simple operation, high flexibility, and low cost, etc. when compared with other microelectronic processing methods. CN33-398 Ag conductor  with a lower resistance was selected as the inductor and the interdigitated electrodes series material. MoS2 nanoflakes (particle diameter: 1.5 μm) were supplied by XFNANO Company, . First, to remove the impurities in the MoS2 nanoflakes. MoS2 nanoflakes (2.0 g) were dispersed in 200 mL deionized water and then magnetically stirred for 10 min, and then the MoS2 nanoflakes were collected by vacuum filtration. After repeating the above process three times, the as-prepared MoS2 nanoflakes were dried at 90 °C and later dissolved with 200 mL of ethanol for further use. As 2 nanoflakes solution was evenly sprayed onto the surface of IDEs at room temperature as the humidity sensitive layer of the sensor. After that, the as-sprayed MoS2 nanoflakes were dried at 90 °C for 5 min to evaporate the solvent.In this work, we fabricated the proposed MoSUnder the same conditions, we fabricated four sensors and the frequency test results of these four sensors at 10% RH and 95% RH of room temperature are presented in 2 humidity sensor. By dint of laser scanning confocal microcopy (LSCM) we investigated the morphology and topography of the as-sprayed MoS2 film and 2 nanoflakes were sprayed evenly on the IDEs and the thickness of the MoS2 thin film was about 32.07 μm. Further, the MoS2 nanoflakes were characterized by the SEM, and the results are shown in 2 nanoflakes is uniform and it has a large surface area to volume ratio. Moreover, owing to the random sequence of nanoflakes, large amount cracks can be absorbed in the SEM image, which may be beneficial for humidity capture. 2 sample prepared by the hydrothermal method. The diffraction peaks of MoS2 nanosheets are observed at 2θ of 14.4°, 33.1°, 39.7° and 58.5°, which were attributed with the MoS2 nanocrystals of (002), (100), (103), and (110) plane. Moreover, the high and sharp diffraction peak (002) of the as-prepared MoS2 samples indicates the sample has good crystallinity and a layered structure.11 data of the humidity sensor in the experimental chamber. According to the simulation results, the frequency sweeping range was set between 150–200 MHz. Note all the tests were processed at room temperature.The sensing performance tests of as-fabricated sensor were arranged in the experimental equipment shown in 11-f curve of the humidity sensor under 10% RH was extracted as shown in 11-f of the as-prepared humidity sensor in a fluctuating humidity environment ranging from 10% RH to 95% RH in increments of 5% RH every 5 min and the S11-f curve of the as-prepared sensor is given as 11 and frequency decrease as humidity variess. Moreover, as the S11 value remained below −6.7 dB all the time, this indicates that the humidity sensor shows a robust signal level from 10–95% RH. Further, by repeating the test procedures in 10–95% RH five times, we obtained the f-humidity curve with error bars as First, the as-prepared sensor was placed in the test chamber and the S2 nanoflakes and the large amount of cracks induced by the random sequence of nanoflakes, water molecules in the ambient can be absorbed by MoS2 nanoflakes. Because of the active defects caused by the Mo atoms on the edge of nanoflakes, the absorbed water molecules were then captured by the defects in the form of Mo-O bonding and ionized by the electric field E between IDEs and dissociated into protons (H+) and hydroxyl ions (OH−) accumulating and mainly distributing on the surface [2 nanoflakes. Due to the low humidity level, the water molecule adsorption on the surface was discontinuous and thus the protons transfer was confined and only happened in the discontinuous water clusters of the surface. Consequently, the dielectric constant shift weakly and the capacitance of IDEs was perturbed in a small range, which account for the low sensitivity in 10–60% RH. At high humidity range (60–95% RH), As shown in 2 and further dissociated into a large amount of protons (H+) and hydroxyl ions (OH−). In this way, proton transfer occurred in the bulk volume of the MoS2 nanoflakes and became continuous in the condensed water. As a result, the dielectric constant shifts acutely and then the sensitivity was significantly improved compared with the sensitivity in a lower humidity range. Also, as the hydrated water dielectric is 2.2 in the low humidity range, the hydrated water dielectric in the high humidity range is 78, which also gave more capacitance improvement of the humidity sensor in the high humidity range (60–95% RH) [As  surface . Then, t–95% RH) ,33.2 nanoflakes are chemically stable to water molecules and the as-prepared humidity sensor has good stability. Also, the hysteresis results shown in Later, we investigated the response and recovery time of the prepared sensor, and frequency-time curve obtained by the experiment is shown in 2 nanoflake wireless passive humidity sensor. The sensor coil is bonded to the alumina ceramic substrate by screen printing technology, which is easy to perform and facile. The sensor structure was optimized by HFSS software simulation and experimental tests show that the prepared LC wireless passive humidity sensor can operate stably at a humidity range of 10~95% RH and has the advantages of high sensitivity and small hysteresis. Under low and high humidity, the sensitivities are respectively 2.79 kHz/% RH and 76.04 kHz/% RH and the response and recovery time of as-prepared sensor is about 10 s and 15 s. In addition, the hysteresis measurements show the sensor has a hysteresis value of 4% RH. Further, it was found that in the 15–40 °C below 80% RH, the temperature has little effect on the sensitivity of the humidity sensor. In summary, the experimental results show that the proposed LC wireless passive humidity sensor can monitor the rapidly changing humidity in a tight, sealed environment.This paper presented a MoS


Scientific and engineering progress associated with increased interest in healthcare monitoring, therapy, and human-machine interfaces has rapidly accelerated the development of bio-integrated multifunctional devices. Recently, compensation for the cons of existing materials on electronics for health care systems has been provided by carbon-based nanomaterials. Due to their excellent mechanical and electrical properties, these materials provide benefits such as improved flexibility and stretchability for conformal integration with the soft, curvilinear surfaces of human tissues or organs, while maintaining their own unique functions. This review summarizes the most recent advanced biomedical devices and technologies based on two most popular carbon based materials, carbon nanotubes (CNTs) and graphene. In the beginning, we discuss the biocompatibility of CNTs and graphene by examining their cytotoxicity and/or detrimental effects on the human body for application to bioelectronics. Then, we scrutinize the various types of flexible and/or stretchable substrates that are integrated with CNTs and graphene for the construction of high-quality active electrode arrays and sensors. The convergence of these carbon-based materials and bioelectronics ensures scalability and cooperativity in various fields. Finally, future works with challenges are presented in bio-integrated electronic applications with these carbon-based materials. Over the past few decades, commercial nanoscale electronic devices, based on semiconductor wafers composed of single-crystal inorganic materials, have achieved high performance with a significant development of fabrication processes. Despite these technological advances, devices with bulky, rigid, and planar materials have limitations for use as flexible or stretchable electronics ,2,3 becaUsing solely biocompatible materials is one of the most significant undertakings in biomedical systems, especially for epidermal electronics ,11 and iOver the last few decades, carbon-based materials such as pyrolytic carbon (PC) and diamond-like carbon (DLC) have been used in the biomedical field. PC has been used in biomedical implants and coating materials, especially in the production of heart valve prostheses . Most PCCNTs have always been controversial in terms of biocompatibility. These conflicting arguments are influenced by the effects of the impurities in CNTs, the length of CNTs, surface chemistry, dispersion interaction between various factors, and experimental variables, including different doses of CNTs, cell population, and evaluation systems . CNTs arThe chemical composition and crystalline structure of both graphene and CNTs are similar. However, some properties of these two materials are different, because the two-dimensional (2D) structure of graphene is fundamentally different from the cylindrical structure of CNT. These materials have different mechanisms of interaction with cell systems, resulting in definite differences in the toxicity of living cells between graphene and CNT. Therefore, the biocompatibility of graphene should be carefully examined separately from CNTs. Recent studies on dispersed graphene flakes using a liquid-phase exfoliation (LPE)  of graphCNTs are considered promising materials for flexible neural interfaces because of their high conductivity and mechanical strength. The electrophysiological signals such as electroencephalogram (EEG) or electrocorticogram (ECoG) are directly affected by the impedance of the electrodes, which lead to the extremely low current injected into the electrodes . High imCNT-based microelectrodes have much higher surface areas than those of flat surface electrodes in the same planar surface as a result of the unique one-dimensional (1D) geometry of CNTs , which gSimilar to CNTs, PEDOT, well known as a representative conducting polymer, has also been regarded as a biocompatible sensing material that provides improved selectivity and enables further surface modification . The eleElectrophysiological signals recorded using novel microelectrodes provide an excellent temporal resolution, but the optical imaging of neural circuits must be followed to achieve both high temporal and spatial resolution ,105,106.Here, we introduce recent advances in transparent and flexible microelectrode arrays, based on CNTs and graphene for simultaneous electrical and optical interaction with brain tissues. Graphene is another candidate for a transparent flexible electrodes arrays because of its ultrathin geometry with a unique two-dimensional structure and mechanical flexibility. Kuzum et al. presented a transparent, flexible neural interface for simultaneous ECoG and calcium imaging, by transferring CVD-grown graphene electrodes on a polyimide substrate a 38]. T. T38]. TThe development of transparent graphene electrode arrays enables the optogenetic stimulation of the underlying brain tissue, as in the case of CNTs, as previously described. Park et al. developed a fully transparent and flexible graphene-based carbon-layered electrode array (CLEAR) by coating the graphene electrodes with Parylene C films e 112]. . 112]. TMicroelectrodes are capable of not only recording the neural signals, but also exciting or inhibiting the action potentials by applying an electrical stimulation to neurons . As the 2/V·s) is much lower than that of a perfectly aligned SWCNT in one direction (~1000 cm2/V·s) . . 161]. TThis review covers some of the latest bioelectronics based on carbon nanotubes and graphene, the most representative carbon nanomaterials. In addition to their high electrical conductivity and optical transparency, excellent mechanical properties that are not found in conventional metal or semiconducting materials have allowed them to be extensively studied as wearable or implantable electronics. However, even though those physical properties of CNTs and graphene are outstanding, they cannot be integrated into the human body if their definite biocompatibility is not established. CNTs and graphene show varying biocompatibility depending on their concentration, method of synthesis, functionalization, and the type of cells to which they are applied. Although most studies using carbon nanomaterials in mammalian cells have shown biocompatibility, careful consideration of the application types is needed, as there are some studies that show toxicity to certain tissues, such as lung and skin. We have introduced biocompatible and flexible CNT/graphene-based bioelectronics that can be applied in epidermal or implantable electronics in two categories, according to their application, namely, microelectrodes and sensors.The surface coating of traditional microelectrodes with CNTs or composites of CNTs and other conductive materials, including PEDOT and gold, remarkably increases the surface roughness, thereby resulting in a high SNR. Furthermore, the high optical transmittance of graphene and CNT thin films enables optical imaging and optogenetic stimulation, at the same time as electrical recording, offering high temporal and spatial resolution. CNTs and graphene with tunable bandgaps are suitable for sensors that detect biomolecules, such as proteins and nucleic acids, with a high sensitivity due to their high mobility and surface area. Recent studies have developed a novel human–machine interface that converts human facial expressions and movements into electrical signals using carbon-based piezoresistive, capacitive, and piezoelectric strain sensors. The integration of various electrochemical sensors and microneedles for drug delivery presents a new scheme that enables the diagnosis and treatment of hyperglycemia with a thin and transparent graphene-based patch.These technological advances in carbon-based materials have contributed greatly to the realization of neural mapping, diagnosis and treatment of various diseases, and to the human–machine interface. Nevertheless, there are still unsolved issues that must be addressed to make these applications even better. Although CNTs and graphene have electrochemical properties that surpass other conventional electrodes for neural interfaces, there are still size-related problems in measuring the activity of all single neurons. To be integrated with a highly stretchable substrate for a more conformal interface with the human body, improved manufacturing technologies, such as low-temperature processes or transfer processes, are required. Furthermore, although many examples of implantable devices have been introduced, there is still a lack of research on devices for long-term usage in the biological environments. For example, CNTs and graphene can be oxidized and peeled off from the electrode surfaces under the electrical stimulation . Establi


The clinical-radiographic distinction between idiopathic pulmonary fibrosis (IPF) and non-specific interstitial pneumonia (NSIP) is challenging. We sought to investigate the gene expression profiles of IPF and NSIP vs. normal controls.n = 22), NSIP (n = 10) and from normal controls (n = 11) was assessed. Microarray analysis included Significance Analysis of Microarray (SAM), Ingenuity Pathway, Gene-Set Enrichment and unsupervised hierarchical clustering analyses. Immunohistochemistry and serology of proteins of interest were conducted.Gene expression from explanted lungs of patients with IPF  contains supplementary material, which is available to authorized users. Idiopathic pulmonary fibrosis (IPF) and non-specific interstitial pneumonia (NSIP) are the most common forms of idiopathic interstitial pneumonia (IIP) . Better The clinical-radiographic distinction is challenging , but is Differential diagnosis between IPF and idiopathic NSIP is based on high-resolution chest CT scan (HRCT) and pathology. Diagnostic radiographic criteria for NSIP are not clearly defined , and as Given the difference in outcomes and response to therapy, we hypothesized that IPF and NSIP exhibit distinct transcriptional profiles, and that specific gene markers may be identified for each condition. As Rosas and Kaminski pointed out, gene expression studies have been highly effective in reclassifying clinically relevant disease phenotypes with similar histologic presentation . The autSpecimens were obtained from the peripheral area of the lower lobe of each lung as soon as the first recipient lung was taken out, snap frozen in liquid nitrogen, and stored at − 80 °C. RNA was extracted and hybridized to the Human Gene 1.0 set array (Affymetrix) from explanted lungs (2001–2008) in 22 patients with clinical diagnosis of sporadic IPF, entirely typical UIP HRCT pattern  and defiThe study was approved by the Human Tissue Committees and Research Ethics Boards of the University Health Network (protocol n.11–0932) and Western University (n.105214).RNA was isolated, labeled, and hybridized to the human gene 1.0 set array according to the manufacturer’s protocols (Affymetrix). Data sets for microarray experiments are available at the Gene Expression Omnibus repository, accession n.GSE110147.Partek software  was used for the preliminary analysis. The q-value  was used to identify differentially expressed genes and was computed with significance analysis of microarray (SAM). For pathways/networks discovery analysis, Ingenuity Pathway Analysis  was used. For Gene-set Enrichment Analysis (GSEA), C5 GeneOntology was used as gene-set database , 18. ForAll IHC slides were reviewed by 2 pathologists. IHC for periostin (POSTN), osteopontin (OPN), p53 and p16, selected ad hoc based on microarray results, was performed using standard techniques.The serum levels of 6 proteins, a priori selected based on literature review ligand-18 [CCL-18]) were measured at baseline and at 4-month intervals for 12 months in 34 patients diagnosed with IPF  and follDetails on sample processing, RNA isolation, complementary DNA synthesis, pre-processing on probe-level data, IPA, GSEA, RT-PCR, IHC and serum measurements are provided in the Additional files P-values < 0.05 were regarded as significant. Prism-4 software package  was used.The Kolmogorov-Smirnov test assessed variables’ distribution. For comparison of groups, either unpaired t test or the Mann-Whitney test, where indicated, was used. Cox proportional hazards regression analysis was used to identify serum biomarkers significantly predicting clinical progression. Receiver operating characteristic (ROC) analysis was used to determine the accuracy of serum biomarkers in predicting clinical progression (c-statistics). There were no significant differences in pulmonary function tests, exercise capacity or pulmonary artery pressures. NSIP patients were significantly younger than IPF patients Table .Table 1DRNA integrity numbers were very similar in the 3 groups: 8.5 ± 0.4 in IPF, 8.8 ± 0.5 in NSIP and 8.6 ± 0.4 in normal controls. Sequential steps in gene expression profiling are shown in Fig. With stringent selection criteria , SAM identified 146 differentially expressed genes, of which 60 upregulated in IPF and 86 upregulated in NSIP. The top 25 upregulated genes in each condition are shown in Tables insulin growth factor binding protein-5 [IGFBP-5], Prominin-1), myofibroblast differentiation and proliferation , collagen deposition , matrix remodeling  peripheral blood mononuclear cells (PBMCs) proliferation and infiltration  and senescence . Most genes were also markedly upregulated in IPF when compared to normal controls. MMP-1 and OPN were the top 2 upregulated genes in IPF compared to controls  in IPF vs. NSIP was confirmed by RT-PCR , ctin ACTA-, OPN), cIPA demonstrated the involvement of relevant genes  in the network “connective tissue disease, organismal injury and abnormality” , the humoral arm of innate immunity  and the recruitment of leukocytes into the lung compartment . The top 25 genes upregulated in NSIP vs. controls are shown in Additional file Genes with significantly increased expression in NSIP, compared to both IPF and normal controls, were involved in regulatory mechanisms of immune reaction, including the alloreactive T cell response  growth factors and SASP matrix remodeling markers. Interestingly, the expression of most genes involved was not significantly increased in IPF  with 79% sensitivity and 73% specificity. Details on ROC analysis are shown in Additional file p = 0.0045). The serum levels of the other biomarkers investigated were not significant predictors of clinical progression , on one hand, and of a combination of senescence and matrix remodelling-related genes  on the other. The existence of this “intermediate” cluster of IPF patients, expressing both NSIP-related and SASP-related genes, cannot be attributed to a mixed histologic pattern, as pathologic diagnosis was confirmed on whole lung explants. Furthermore, all IPF cases in this study featured an entirely typical HRCT pattern of UIP.Considering the interesting observations of radiographic “evolution” of biopsy-proven NSIP cases into an UIP/IPF pattern , and theComprehensive gene expression profiling from whole lung explants aligns separate, well-recognizable histopathologic patterns of IIP with distinct transcriptional profiles and differentially expressed genes, and does not support the notion of NSIP as an early manifestation of IPF, but rather point to a standalone, transcriptionally homogenous condition, even in advanced fibrotic cases requiring LTx. LRP-2 and IFI-44 were identified as candidate molecular markers of NSIP, further validated against normal controls. This, however, does not exclude that “senescent” NSIP itself may represent a risk factor for developing IPF, given the remarkable degree of transcriptional overlap observed in a subgroup of IPF cases. Senescence-related genes are indeed prominent in IPF: we identified IGFBP-5 as a candidate molecular marker specific for IPF; p16 as a candidate fibroblast protein marker of IPF; and POSTN serum levels as better predictors of clinical progression, although not specific for IPF. These findings will likely stimulate validation studies in smaller, routinely available biopsy samples, as well as in larger populations.Additional file 1:Figure S1. A. Probe intensity histogram. B. F ratio: signal-to-noise ratio, IPF vs. NSIP analysis across the whole genome. The bar indicates the average signal for all genes. The height of the bar is the mean square. UIP=IPF (JPG 57 kb)Additional file 2:Figure S2. Principal component analysis, a global analysis across the whole genome. IPF and NSIP groups are shown. UIP=IPF. (JPG 114 kb)Additional file 3:Table S1. Top 25 upregulated genes in IPF vs. control . Table S2. IPF vs. control, Ingenuity Pathway Analysis (IPA). In IPA, “functions” are divided in 3 categories: “disease and disorders”, “molecular and cellular functions” and “physiological system development and function”. Table S3. Top 25 upregulated genes in NSIP vs. control . Table S4. NSIP vs. control, Ingenuity Pathway Analysis (IPA). In IPA, “functions” are divided in 3 categories: “disease and disorders”, “molecular and cellular functions” and “physiological system development and function”. Table S5. Gene expression of cellular senescence biomarkers in IPF vs. NSIP and vs. normal controls. Significantly upregulated genes are indicated with *. Pro- and anti-fibrotic properties of metalloproteinases (MMPs) are indicated in brackets under the gene name. Table S6. Summary of immunohistochemistry findings in IPF and NSIP. Table S7. Receiver operating characteristic (ROC) analysis of serum biomarkers vs. 12-month clinical progression. (DOCX 47 kb)Additional file 4:Figure S3. Comparison of gene expression levels determined by oligonucleotide microarray (left) and by quantitative RT-PCR  in the IPF and NSIP groups: A. MMP-7. B: OPN. C. IGFBP-5. (JPG 81 kb)Additional file 5:Figure S4. Ingenuity network analysis, networks with highest scores. Networks were scored based on the number of network eligible molecules they contained. Network eligible molecules with relatively increased expression are shown in red, whereas molecules with relatively reduced expression are shown in green. The intensity of the color is proportional to the fold change. Non-colored nodes represent genes added by Ingenuity pathway analysis based on its network algorithm but not upregulated in the actual microarray data. A. Network “Connective tissue disease, organismal injury and abnormality, cancer” (score = 29). Network eligible molecules with relatively increased expression in the IPF group are shown in red, whereas molecules with relatively increased expression in the NSIP group are shown in green. B. Network “Anti-microbial response, inflammatory response and cancer” (score = 42). Network eligible molecules with relatively increased expression I the NSIP group are shown in red. (JPG 53 kb)


A combination of carbon nanotubes (CNT) and graphene in the form of macroscopic hybrid buckypaper (HBP), exhibits a unique set of properties that can be exploited for many emerging applications. Here, we present a simple, inexpensive and scalable approach for the synthesis of highly conductive auxetic graphene/CNT HBP via wet-filtration-zipping and demonstrate the electrical, electrochemical and mechanical performance  of synthesized HBP. An overall increase in electrical conductivity of 247% is observed for HBP (50 wt.% graphene and 50 wt.% CNT) as compared to BP (100 wt.% CNT) due to effective electronic percolation through the graphene and CNT. As a negative electrode for lithium-ion batteries, HBP shows 50% higher gravimetric specific capacity and 89% lower charge transfer resistance relative to BP. The graphene content in the HBP influences the mechanical performance providing an auxetic structure to HBP with large negative Poisson’s ratio. The facile green-chemistry approach reported here can be readily applied to any other 1D and 2D materials and solves key challenges associated with existing buckypaper manufacturing methods. The potential of the synthesis method to integrate with current cellulose paper manufacturing technology and its scalability demonstrate the novelty of the work for industrial scale production. The origin of exceptionally high Young’s modulus, 1.2 TPa, electrical conductivity, 106 S/m, and thermal conductivity, 3000 W/mK, are due to the bond strength of sp2 hybridized carbon, out of plane π-orbitals with unique band structure, and phonon transport, respectively6. They are highly sought for advanced energy, structural and electronic applications9. Due to their microscopic nature, they are difficult to handle and therefore need a macroscopic assembly for real world applications. Carbon nanotube papers 37, graphene papers, graphene oxide (GO) papers, reduced graphene oxide (rGO) papers, GO/rGO-CNT hybrid BP (HBP), and graphene-CNT HBP are some of the macroscopic assemblies which represent the outstanding nanoscale material properties in macroscale form, leading to the creation of strong, foldable, auxetic and highly conductive lightweight materials. These assemblies, in particular, HBP combines 1 dimensional (1-D) properties of CNT and 2 dimensional (2-D) properties of graphene in a single 3-dimensional (3-D) macroscopic structure. Moreover, these assemblies are important in various applications, such as in water and air purification39, energy storage40, sensors42, aviation44, medical devices46, composites48 etc. Another interesting aspect of BP/HBP is that the realignment of entangled nanotubes during stretching gives a large negative Poisson’s ratio, and such materials are usually termed auxetic materials. Auxetic materials have various applications, such as press-fit fasteners, curved sandwich panels, flexible impact buffers, soundproof materials, and so on13. Recent progress in multi-walled CNT (MWCNT) and graphene production provides these materials at scalable quantity50. Concomitantly, the manufacturing of BP/HBP also needs a low-cost, simple, scalable procedure to convert the CNT and graphene powder into BP/HBP.Carbon nanotubes (CNT) and graphene consist of st method, BP is directly produced during CNT growth by chemical vapor deposition - also known as CVD method21 or post-CNT synthesis using dry techniques of shear pressing, alcohol drenching and pressing, domino pushing and CNT drawing. A disadvantage of this technique is that the resulting BP is typically not thick. Moreover, the production process is not roll-to-roll. In the 2nd method, BP is produced by powder compaction and frit-compression. However, the powder compaction requires a mold, thus the created BP may not be flexible nor foldable. Despite the thicker BP compared to 1st method, frit-compression technique requires a relatively high cost membrane which hinders scalability. The 3rd method involves techniques such as drop casting30, rod coating27, air spraying, and tape-casting26. Yun et al. described the fabrication of BP using tape-casting on a mold followed by vacuum oven heating15. The need of mold as well as vacuum heating process may hamper this method’s scalability. Moreover, it is problematic to detach the CNT layer/film from the supporting substrate to get freestanding BP due to low surface energy of CNT. Recently, to overcome this problem, Susantyoko et al. developed a surface-engineered tape cast method to manufacture flexible, freestanding, and foldable BP on a roll-to-roll system without the usage of mold16. However, a special need for surface-engineered conveyor belt limits its use in the laboratories. The 4th method is the membrane filtration38, which can be effortlessly installed in laboratories. Despite the common usage of this method, challenges of the membrane-filtration method include membranes with a relatively high-cost; requirement of hazardous chemicals; requirement of vacuum; requirement of high pressure; long filtration time due to the high fluid flow resistance (particularly for thick BP); relatively small BP diameter ; and relative non-uniform BP thickness. Because membrane filtration has a low-throughput, it may not be a potential candidate for mass production of BP. We solved these challenges using environment-friendly water based wet-filtration-zipping. In this method water with the surfactant is used to disperse the hydrophobic MWCNT and graphene to obtain their well dispersed solution. We use inexpensive cellulose filter papers with relatively large pore size (11 µm) and thickness (180 µm) to obtain MWCNT and graphene sediment on it by gravity. Further, MWCNT-graphene sediment was zipped due to elasto-capillary densification and thus a freestanding BP/HBP54 is formed. Our process has the potential to integrate with the current industrial paper manufacturing technology. Other advantages are scalability, uniform thickness (at micron level), and potential of the synthesis route to accommodate any other 1D and 2D materials .The HBP production is new and mostly utilizes the existing BP production methods. Four major BP production methods have hitherto been reported in the literature. In the 155. However, there are few limitations of graphitic anode such as low specific capacity and mediocre rate capability, warranting further research to advance the performance of carbon-based anode materials. CNT and graphene are promising candidates for large capacity lithium-ion batteries due to their excellent conductivity as well as stability. In addition to the high specific surface area, the two sides of graphene sheets, and internal as well as external walls of CNT can be fully utilized to store lithium ions to form LiC3, thereby raising anode theoretical specific capacity (744 mA h g−1) to more than twofold of the graphite (has a lower surface area and forms LiC6 during lithiation) specific capacity (372 mA h g−1). Consequently, the right selection of material and appropriate architectural design modification are crucial for excellent battery performance. It is expected that the combination of CNT and graphene in HBP will improve the anode performance. Therefore, the anodic performance of binder free HBP is evaluated using cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic cycling measurements with lithium metal as the counter electrode.Another aim of this work is to study the electrical, electrochemical and mechanical performance of BP/HBP. We have demonstrated potential application of HBP as an anode for lithium-ion batteries. The anode is one of the most important part of lithium-ion batteries since the anode characteristics influence their electrochemical performance. Incumbent anode utilizes graphitic carbon because of its advantageous features, such as the excellent electrical conductivity, beneficial hierarchical structure for the intercalation of lithium ion, low-cost and abundant availabilityAs such, without any chemical bonding and binder, these free-standing self-assemblies are held together due to entanglement and weak van der Waals interaction. It is important to understand the tensile and fracture behavior of such assemblies. Therefore we also focused on evaluating their tensile properties and fracture resistance in mode I and mode III, and identified the corresponding failure mechanisms.50. MWCNT are synthesized by a continuous atmospheric CVD system with a glass fiber fabric substrate49. The diameter of MWCNT is within 10–30 nm range with 3–10 walls  is much higher than that of the ethanol (23 mN/m) and acetone (25.2 mN/m) and therefore higher densification is expected in the case of water. It is expected that the weak van der Waals forces, entangled network of MWCNT and covalent bonding in MWCNT shared walls are responsible for holding the whole BP/HBP assembly. Moreover, MWCNT and GC are not functionalized and therefore other chemical bonding such as hydrogen and hydroxyl is absent. The lateral dimensions of BP/HBP depend on the size of the metal tank whereas the thickness of BP/HBP depends on the amount of MWCNT and GC thus allowing scalability over lateral size and thickness  produced at industrial scale are used for the fabrication of buckypaper (BP) and hybrid buckypaper (HBP)Surface morphology of as-prepared (uncompressed) and compressed BP observed in SEM is shown in Fig. As prepared (uncompressed) and compressed HBP show a distinct surface morphology as compared to BP Fig. . Apart f2–106 S/cm. The difference in the electrical properties of our HBP and the MWCNT/graphene is due to the discontinuity between the individual MWCNT/GC and the weak electrical conductivity between the contacts of MWCNT–MWCNT, MWCNT–GC, GC-GC. In comparison with the electrical properties of published work of BP/HBP, our BP exhibits properties similar to BP with randomly oriented CNT, and our HBP with HBP comprising self-assembly of CNT-graphene. However, our BP/HBP exhibits marginal properties compared to the BP with oriented CNT and HBP with chemically bonded CNT-graphene. The difference in these properties comes from various parameters such as graphene type , CNT diameter and length, alignment, density, graphene flake size, chemical treatment, processing condition, fabrication method, nature of bonding between CNT and graphene, etc.The GC content and compressed HBP show an ameliorating effect on the electrical conductivity Fig. . The ele−1 discharge rate had 1st, 2nd, 50th and 100th cycle specific capacity of 821.4, 204.8, 149.6 and 149.7 mAhg−1, respectively. BP has specific capacity of 1065.5, 218.8, 88.8 and 101.9 mAhg−1 at 1st, 2nd, 50th and 100th cycle, respectively. The superior specific capacity of HPB after cycles can be attributed to secondary lithium-ion storage mechanism in the disordered stacks of graphene sheets. The specific capacity drop from 1st cycle to 2nd cycle of 616.5 mAhg−1 of HBP is lower than that of BP of 846.653 mAhg−1. Electrochemical impedance spectroscopy (EIS) was performed and the data was fitted using equivalent circuit in Fig. 57. However, being a freestanding structure, the HPB does not have dead weights from metal current collectors, which set it apart from references57. In short, the right selection of material, and appropriate architectural design modification are crucial for excellent performance of battery. As a result, the combination of MWCNT and graphene in HBP improves the anode performance.Figure 58.BP and HBP are highly desirable next generation carbon-based materials which have potential to replace the carbon fibers in multifunctional composites. It incorporates the outstanding properties of 1D CNT and 2D graphene. In this regard, mechanical properties of both BP, and HBP are important. Tensile response of BP and HBP are shown in Fig. 60. The compression further improves the mechanical performance of BP and HBP  test. The details of the tests are provided in the Methods section, and geometric parameters and dimensions of DENT specimen are provided in the Supplementary Information Figure . Figure entclass1pt{minimaet al. observed the stick-slip tearing in graphene oxide papers intercalated with CNT. The stick-slip behavior has also been observed in thermoplastic elastomers and polyvinyl alcohol gel sheets66, and in layered structures with low interfacial properties67. The as-prepared BP shows tearing toughness of 879 J/m2 whereas the as-prepared HBP shows the tearing toughness of 288 J/m2  anode shows 50% higher specific capacity and 89% lower charge transfer resistance relative to BP (100 wt.% MWCNT). In cyclic test, HBP anode shows excellent Columbic efficiency and very low cycle to cycle capacity fading. The GC content in the HBP influences the tensile performance giving a large negative Poisson’s ratio. The presence of GC flakes in the MWCNT network aids higher transverse expansion with load and results in negative Poisson’s ratio. The fracture resistance of BP and HBP is studied in two different modes, including mode I fracture using the DENT test and mode III tearing test using the trouser test. The BP shows the average fracture toughness 1.11 MPa mGraphene CrystalTM KAUST-Saudi Arabia. The details about the GC are provided in the patent. The GC are graphene flakes with less than 10 layers containing defect-free graphene lattice (sp2 hybridized C-C bonding) over the full range of basal plane. The flake size is less than 300 µm. Multi-walled carbon nanotubes/nanostructures (MWCNT) were obtained from Applied Nanostructured Solutions, LLC. MWCNT flakes consist of bundles of aligned MWCNT. Sodium dodecyl sulfate (CH3(CH2)11OSO3Na) surfactant was purchased from Sigma Aldrich (CAS Number 151-21-3).Few-layer graphene flakes in a powder form ) were obtained from spin-off Schematic of wet-filtration assembly is shown in Fig. The fabrication of BP/HBP starts with dispersing MWCNT and GC in water using the surfactant. In a typical experiment, MWCNT and GC were weighted in the range of 100 mg to 1000 mg using microbalance with the accuracy of 1 mg. The weight ratio of MWCNT and GC was varied to obtain the HBP. A BP contains only MWCNT whereas HBP contains MWCNT and GC in a different weight ratio. We also tried to obtain only GC paper but it was difficult to peel it off from the filter paper due to the weak interactions between two GC. In a glass beaker, 1 g SDS was dissolved in a 1 l water. The weighted MWCNT and GC were very easily mixed with water due to the presence of surfactant. The solution was subjected to 24 h ultra-sonication using a tip-sonicator with a 15 s ‘on’ and 10 s ‘off’ pulse of 40% amplitude and 500 W power. It was observed after 24 h that the dispersion clear black solution is obtained, moreover, the solution stays stable for the several days indicating proper dispersion of MWCNT and GC in the water   and transmission electron microscope . Monochromator and image corrector were used to acquire high-resolution TEM (HR-TEM) images at 80 kV. Spectroscopic characterizations were carried out using Raman confocal spectroscopy using WITec confocal Raman spectrometer with an excitation wavelength of 532 nm  was taken using a precision balance  with a readability of 0.01 mg. Coin cells of 2032-type were assembled using a crimping machine (MSK-110 Coin Cell Crimping Machine) inside a glovebox (MBraun MB-Labstar 1450/780). The liquid electrolyte used was 1 M LiPF6 in EC:EMC (1:1 vol%) with 2 wt.% FEC. A half-cell configuration was used in which a lithium metal foil serves as counter and reference electrodes. Coin cells were tested using a battery tester (Maccor Battery Test System Series 4000) inside an environmental chamber (CSZ Model MC-3 Chamber) at a constant temperature of 25 °C. Battery testing was performed using constant current charge discharge (CCCD) at various rates with a potential limit between 0.01 and 3 V vs. Li/Li+. The BP/HBP sheets were also cut as 5 mm disk samples to be assembled in coin cell configuration for rate-capability and cyclic voltammetry tests. Cyclic voltammetry was conducted at scan rate of 0.1 mV s−1 from 0.01–3.0 V vs. Li/Li+, using a multi-channel potentiostat/galvanostat (Princeton Applied Research PMC-1000) without iR compensation. The specific capacities were calculated by considering the mass of the whole electrodes = mass of MWCNT + mass of graphene. Electrochemical impedance spectroscopy (EIS) measurements were performed obtained using an Autolab PGSTAT302N; the acquisition of the impedance spectra was done near open circuit potential (at 1.4 V) with ac frequencies between 106 Hz to 2.3 × 10−3 Hz and ac amplitude of 10 mV.The BP/HBP were cut as 12 mm diameter disks. The mass loading (average of 3.1 mg cm3 were performed in Zwick-Roell Z005 device with a 20 N load cell at ambient temperature (~20°C). The tensile load was applied at a constant crosshead speed of 200 μm/min. To reduce stress localization in the grip zone, tab made from thick adhesive tape was used. DIC technique was used for full-field measurement of strain on the specimens. White speckle patterns of acrylic paint were applied on the black surface of BP/HBP using an airbrush prior to testing. Consecutive speckle images were acquired as a function of load using a monochrome 5.0 MP camera for strain evaluation. The average engineering strain in the axial and lateral directions over the gauge length zone was evaluated using Vic-2D software. These strain values were then used to construct the engineering stress‒engineering strain curve and to evaluate the Poisson’s ratio. Further details on DIC experimental setup can be found in58.Tensile tests of the BP/HBP with sample size of 60 × 6 × (thickness) mm68:The mode I fracture toughness of BP/HBP was evaluated using double edge notched tension (DENT) specimen configuration. The tensile load was applied at a constant crosshead speed of 200 μm/min using the Zwick-Roell machine with a 20 N load cell at ambient temperature (~20°C). The specimen with ligament length mentclass2pt{minimThe strain energy release rate F is the mean force over the entire ligament length; and The trouser tear tests were performed to evaluate the resistance to tear propagation of BP/HBP. The tests were conducted on the Zwick-Roel Z005 machine with 20 N load cell at cross-head speed of 2 mm/min. The critical tearing energy Supplementary Information


In this paper, a series of fluorinated graphene materials are prepared by using N, O-doped graphene aerogel as precursor via a direct fluorination method, and the effect of fluorination temperature on the FG structure is investigated. The prepared FG samples are systematically characterized by scanning and transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and Raman spectroscopy. It is found that the structure of FG, including features such as layer size, chemical composition, chemical bond state of the component elements, etc., is significantly related to the fluorination temperature. With the change of the fluorination temperature, fluorine atoms enter the graphene framework by a substitution process of the N, O-containing groups, including residual phenol, ether, carbonyl groups, or C–N groups, and the addition to CC bonds, subsequently forming a fluoride with different fluorine contents. The fluorine content increases as the fluorination temperature increases from 200 °C to 300 °C, but decreases at a fluorination temperature of 350 °C due to the decomposition of the fluorinated graphene. The prepared FG samples are used as cathode material for lithium primary batteries. The FG sample prepared at 300 °C gives a high specific capacity of 632 mAh g Graphene-based materials have attracted great attention in nanotechnology because of their amazingly attractive properties, such as high theoretical specific surface area (2630 m2 g−1), superior electron mobility, easy self-assembling into three-dimensional (3D) macroscopic materials with controlled microstructures, high mechanical, chemical, thermal, and electrochemical stabilities, etc. Therefore, graphene-based materials have already been widely applied in many fields, including but not limited to nanoelectronics . T. T2 and–3 hybridization of carbon atoms) to semi-ionic (sp2 hybridization of carbon atoms), as shown in 2 hybridization structure of FG-350 results in a weakness of the intensity of its C–F bonds. From the O1s spectra of RGOA  and C–NH–C (400.3 eV), which are formed via the reaction between EDA and the oxygen-containing groups. The change of the N1s peak in  of RGOA b, we cou−1, 1662 cm−1, 1532 cm−1 and 1114 cm−1, which are attributed to the stretching vibration peak of –OH, the C=O stretching vibrational peak, the bending vibration absorption peak belonging to carbonyl, and C–O–C vibration absorption peak, indicating the existence of –OH, –COOH, C–O–C, –C=O. Moreover, the peaks at about 1386 cm−1 and 1580 cm−1 are assigned to –CH2 and N–H groups. The formation of these groups can be attributed to the EDA-mediated nucleophilic ring-opening reaction of epoxy groups on the surface of GO according to the previous report [−1 corresponding to the characteristic vibrational mode of C–F bond [−1, 1217 cm−1, 1226 cm−1, and 1190 cm−1 for FG-200, FG-250, FG-300, and FG-350, respectively. The C–F peak of FG-350 shows a significant red-shift, and the peak at 1572 cm−1 increased, further indicating the weakness of C–F bond and the increase of O content. The change trend exactly coincided with the XPS results. The chemical structures of RGOA and FG were further studied by infrared spectroscopy a. It cans report . After fC–F bond . The exa2 and –CF3 groups on the surface, thus resulting in the partial recovery of π–π stacking of the graphene sheets for FG-350. Moreover, a weak peak at about 8.6°, corresponding to a large layer spacing of about 1.1 nm, was found for FG-350. This could be explained by the high content of N, O elements (the oxygenated groups and bridge-linked amide groups). The crystal structures of FG and RGOA were also characterized by the Raman spectra, which are shown in −1 and 1590 cm−1, respectively. The presence of D peaks is a typical feature of chemically synthesized graphene. In general, the D peaks are closely related to the disorder in the graphene, and the G peaks are attributed to the first-order scattering of the stretching vibration mode E2g observed for the sp2 carbon domain. A slight upshift of the G band from 1593 to 1605 cm−1 for the fluorinated samples was attributed to the formation of the C–F bond [As shown in C–F bond .+/Li. As shown in −1. No discharge potential platform was observed for FG-200 and FG-350, which may be related to its low fluorine content [−1, 375 mAh g−1, 569 and 30 mAh g−1 for FG-200, FG-250, FG-300, and FG-350, respectively. These values are proportional to the fluorine content, but much lower than the theoretical ones according to the F/C ratio, since the fluorinated samples investigated here possess many –CF2 and –CF3 groups, which are proved to be non-electroactive [−1. As shown in −1 and 430 mAh g−1 at 10 mA g−1 and 500 mAh g−1, corresponding to energy densities of 1485 Wh kg−1 and 731 Wh kg−1, respectively. It should be noted that there no apparent output potential delay was found at a high current density of 500 mA g−1 due to the large compact surface between the Li+ and the 2D fluorinated graphene. Finally, the discharge behavior of FG-350 was investigated, and the results are shown in + [The prepared fluorinated graphene materials were investigated as Li-primary battery cathode.  content . The disroactive . Next, wown in + .2 hybridization structure. Due to the large amount of oxygen groups in RGOA, CF2 and CF3 are produced during the fluorination process, which reduces the electrochemical performance of the fluorinated graphene as cathode materials of lithium primary batteries. The discharge capacity of FG-300 is calculated to be 632 mAh g−1 at 10 mA g−1, corresponding to energy densities of 1485 Wh kg−1, which are the highest ones among the investigated samples.We have developed four fluorinated graphene materials by using a scalable method of direct fluorination. N, O co-doped fluorinated graphene nanosheets exhibit high fluorine content and amorphous microstructures with two-dimensional nanostructures. The structure of the fluorinated graphene is proved to be very sensitive to the fluorination temperature. As the fluorination temperature increases from 200 °C to 350 °C, the fluorine content firstly increases and then significantly decreases. The high fluorination temperature leads to a decomposition of C–F, thus resulting the loss of fluorine and partial restore of sp


With the integration and miniaturization of electronic devices, thermal management has become a crucial issue that strongly affects their performance, reliability, and lifetime. One of the current interests in polymer-based composites is thermal conductive composites that dissipate the thermal energy produced by electronic, optoelectronic, and photonic devices and systems. Ultrahigh thermal conductivity makes graphene the most promising filler for thermal conductive composites. This article reviews the mechanisms of thermal conduction, the recent advances, and the influencing factors on graphene-polymer composites (GPC). In the end, we also discuss the applications of GPC in thermal engineering. This article summarizes the research on graphene-polymer thermal conductive composites in recent years and provides guidance on the preparation of composites with high thermal conductivity. Thermal management has become a crucial issue in the modern electronics industry as electronic devices have become more integrated and miniaturized. The power required for some processor modules can reach 250 W in a high-performance computer, leading to heat loads as large as 1 kW in this system [−1 K−1 [Polymers have a lot of advantages, such as being lightweight, low cost, easy to process, and exhibiting good corrosion resistance. However, most polymers are heat insulators and have a thermal conductivity between 0.1 and 0.5 W m−1 K−1 , which i−1 K−1 . PhononsIn past years, a lot of works have studied thermal conductive polymer-based composites. Many different materials with high thermal conductivity have been used as fillers to improve the thermal conductivity of composites, such as boron nitride (BN) ,7,8,9, c−1 K−1, which was one of the highest thermal conductivities of currently known materials [Graphene has attracted great attention because of its unique two dimensional 2D) structure and novel properties, such as the zero-gap band structure, high electron mobility, and high thermal conductivity . Balandiaterials . AlthougD structuaterials ,4. In thIn this article, we review the advances in thermal conductivity of graphene-polymer composites in recent years. Special attention is given to the mechanism, the properties, and the influence factors of graphene-polymer composites. Additionally, we discuss the applications of thermal conductive graphene-polymer composites.−1 K−1 at room temperature, and the attribution from phonons is limited to 1–2% of the total [In solid materials, heat is carried by phonons and electrons . In metahe total . The thehe total . Howeverhe total . Figure he total . When onhe total ,31,32. Ihe total ,34,35,36Thermal conduction through a polymer is a complicated process, which is influenced by many parameters like crystallinity, temperature, orientation of the macromolecules, and so on ,38,39. PThe thermal conductive mechanism of graphene in polymers is more complex. In general, graphene has a very high specific surface area. When being added in a polymer, large numbers of interfaces are produced . These iIn recent years, more studies have been using graphene and its derived materials to prepare thermal conductive composite materials. The morphology of graphene in the polymer matrix significantly affects the thermal conductivity of the composites . In thisGraphene with a random orientation in the polymer matrix can be manufactured by many methods, such as solution mixing, melt mixing, and in-situ polymerization, etc. ,50,51,52There are a variety of specific orientations of graphene in the polymer matrix, such as orientation, segregated structure, 3D structure, and so on ,73,74,75There are many factors affecting the thermal conductivity of graphene-polymer composites, such as the defects on graphene, the orientation of graphene in the polymer, the graphene loading, and the surface modification, etc. ,4,5. In 3 W m−1 K−1 to ~4.0 × 102 W m−1 K−1 near room temperature as the density of defects changed from 2.0 × 1010 cm−2 to 1.8 × 1011 cm−2 [−1 K−1. This is because the high-temperature annealing heals defects and removes oxygen functional groups on graphene, thus reducing the phonon scattering centers [The characteristics of graphene have a great influence on the thermal conductivity of graphene-polymer composites ,91,92,93011 cm−2 . Xin et  centers . The mor centers . Kim et  centers . Kim et  centers .The loading of graphene exerts a significant effect on the electrical and thermal conductivity of the composites ,99,100. −1 K−1, which is higher than copper at room temperature. It is claimed that this dramatic enhancement is attributed to the rapid and effective heat-transfer path formed by orientated graphene [−1 K−1, 20% higher than that of GS/PDMS composite at the loading of 0.7 wt %. They believe that the unique interconnected structure of GF acts as an efficient thermal pathway in the polymer matrix [Many researchers believe that graphene with a specific orientation, like orientation and 3D structure, is much better than graphene with a random orientation when preparing thermal conductive composites ,88,89,90graphene . Zhao etIt is considered that the interface between graphene and the polymer plays an important role in thermal conductive composites. Since phonons are the main form of thermal conductance in graphene-polymer composites, bad coupling in vibration modes at the graphene-polymer interface will generate huge interfacial thermal resistance. Chemical bonding between graphene and the polymer can efficiently decrease the phonon scattering at the interface and reduce interfacial thermal resistance . Gao et Nowadays, with the improving demand in emerging industries, thermal conductive materials with novel properties are widely required ,108,109.2 and junction-to-ambient thermal resistance of less than 0.2 °C/W [−1 K−1. Employing graphene to prepare a thermal conductive material as TIM has been attracting a lot of attention.In the electronic industry, thermal management has been a serious challenge because of the miniaturization and functionalization of electronic devices. To control the temperature of all components in devices, an effective thermal conductive path must be used . Thermal−1 K−1, which is about 14 times that of the OA [The effort towards thermal energy storage has been intensified over the past years. Thermal conductivity is an important parameter in thermal energy storage materials, which significantly influences the rate of heat storage and extraction . Therefof the OA .−1 K−1. They think Lithium-ion batteries have become the major source of power for portable electronic devices. Separators are one of the major components of these batteries, and the improvement of thermal conductivity in separators is an option for long-lasting Li-ion battery fabrications [As batteries have become more powerful in recent years, thermal management has turned into a special issue in the battery system. When a battery is used at a high charging/discharging rate, the rate of heat generation may exceed the rate of heat dissipation. In this situation, the battery may be inefficient or even catch fire. A thermal management system is needed to maintain the battery pack at an optimum temperature. Khan et al. incorporated 8 wt % graphene nanoflake in polyacrylonitrile (PAN) fiber separators, and the thermal conductivity increased from 3.5 to 8.5 W mications . Hallaj ications .In this paper, we have reviewed the graphene-polymer thermal conductive material in recent years. The thermal conductive mechanisms in graphene, polymers, and their composites have been discussed. The recent advances on thermal conductivity of graphene-polymer composites have also been reviewed. Furthermore, we have discussed the factors influencing the thermal conductivity of graphene-polymer composites, such as the characteristics, the loading, the orientation of graphene, and the interface. Finally, the applications of thermal conductive graphene-polymer composites have been demonstrated. This review reveals the relationship between thermal conductive mechanisms and properties and also provides guidance on the preparation of composites with high thermal conductivity.