The composites displayed excellent conductivity of 13.68 S·cm−1 with 3.1 Ω·sq−1 lowest sheet resistance. All the composites showed an outstanding thermal stability and constrain highest weight lost until 400 °C. The MXene-graphene foam exhibited excellent EMI shielding of 53.8 dB (99.999%) with reflection of 13.10 dB and absorption of 43.38 dB in 8–12.4 GHz. The single coated carbon fabric displayed outstanding absolute shielding effectiveness of 35,369.82 dB·cm2·g−1. The above results lead perspective applications such as aeronautics, radars, air travels, mobile phones, handy electronics and military applications.MXene and graphene based thin, flexible and low-density composite were prepared by cost effective spray coating and solvent casting method. The fabricated composite was characterized using Raman spectroscopy, X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray (EDX). The prepared composites showed hydrophobic nature with higher contact angle of 126°, −43 mN·m The cross link/hydrogen bond between constituents cause by surface functional groups. The cross links improve the thermo mechanical properties [The rapid advancement in intricate packing of modern electronic systems causes undesirable radiation; this inevitable radiation is known as electromagnetic interference (EMI), which has negative effects on humans and neighboring electronic systems. EMI pollution causes health hazards such as languidness, insomnia, nervousness, and headaches ,2,3,4. Eoperties ,27,28. Foperties . Advanceoperties ,32,33,34Recently, flexible, corrosion resistant, high-density, thin carbon-based materials with satisfactory electrical conductance have become attractive candidates for EMI shielding applications such as in the aerospace, aircraft, automobile, and modern electronics fields. Hence, wet-laid synthetic nonwoven fabrics fulfil these criteria with good EMI shielding . In addin+1XnTx , where M is an early transition metal, X is carbon or nitride, and Tx is a surface functional group . MXenes are generated from the corresponding layered MAX phase with the general formula Mn+1AXn by selective engraving of the A-layer (group 13/14 elements) created by a weak M-A bond sandwiched between a strong M-X bond. Minimally intensive layer-delamination (MILD) etching is carried out using the LiF/HCl method, which is advantageous over clay etching in which Hydrogen fluoride (HF) is utilized under various etching conditions [4OH, tetrabutylammonium hydroxide (TBAOH), and sonication. These exfoliation techniques are inevitable in the clay method. However, LiF/HCl-based in-situ mild etching is highly preferable owing to the number of steps, level of defects and risk, and the fact that exfoliation can be achieved through manual shaking. However, sonication at low temperature and in inert environments (Ar) is preferable [Two-dimensional MXenes are explored intensively for various applications including EMI shielding. MXenes are sprouting transition metal  carbides/nitrides with universal formula Mnditions ,45,46,47eferable . MXene teferable ,35.In this study, we develop a graphene-flake (GN) coated carbon-fiber reinforced-matrix composite (MC) and solution-casting MXene graphene foam, which exhibit a high EMI shielding effect in the S-band region. The required thickness is achievable by adjusting the spraying and drying cycles. Further, we developed MXene graphene foam with internal hollow sphere with surface imbedded balls. Consequently, we analyze the following parameters in detail; EMI shielding, morphology of GN-coated matrix and MXene-graphene foam, electrical conductivity, constitutional chemical species, elemental percentage, and hydrophobic nature. In addition, the pristine carbon-fiber-reinforced matrix composite, graphene, graphene oxide, and reduced graphene oxide are denoted as MC, GN, GNO, and rGNO, respectively. The GN, GNO and rGNO coated fabrics are denoted as GNMC, GNOMC, and rGNOMC, whereas the MXene-graphene coated fabric, MXene-graphene composite, and MXene-graphene oxide composite are symbolized as MGNMC, MGNC, and MGNOC, respectively.w/w%, lithium fluoride (LiF) , Polyacrylic acid (PAA), and Polyacrylamide (PAM) were purchased from Sigma Aldrich . Polyvinylidene fluoride (PVDF) (melting point of 155–166 °C) was purchased from Alfa Aesar . Hydrochloric acid (HCl-35%) and nitric acid (HNO3-70%) were supplied by Samsung Chemical Co., Ltd. , anhydrous lithium chloride (LiCl) was purchased from Tokyo Chemical Industry Co., Ltd , and Ti3AlC2 was acquired from Forsman Scientific Co., Ltd. . Carbon fiber  and polyethylene terephthalate (PET) binder  were purchased from TORAY Product . No purification methods other than those stated were utilized for the chemicals.Graphene (GN)  was obtained from Ditto Technology Co. Ltd., . Dimethylformamide (DMF) 99.8 3 and stirred at room temperature for 12 h. The reacted graphene was washed with deionized water until it reached a neutral pH. The resulting black flakes were GNO, and these were dried at 80 °C for 24 h. Equal amounts of GNO and NaBH4 were mixed together in deionized water and stirred at room temperature for 12 h. The resultant product was washed several times with deionized (DI) water and dried at 80 °C for 24 h. The obtained product was rGNO.A total of 1 g of graphene was mixed with 50 mL of HNO3AlC2 and LiF were immersed in 20 mL of 6M HCl solution and stirred at 35 °C for 24 h. The resultant mixture was washed with DI water (pH 6) several times by centrifuging at 3500 rpm for 5 min, and the black flakes were dried at 100 °C for 12 h in a vacuum oven. A total of 0.1 g of MXene was dispersed in 10 mL of DI water by sonication for 1 h in an ice bath. The resultant exfoliated solution was centrifuged at 3500 rpm for 30 min. The supernatant was collected and stored at 5 °C for the coating process.Equal amounts of Ti−1. The obtained fabric density was 20 g·m−2.Carbon fiber, PET-binder fiber with a 4:1 weight ratio, and 0.3 wt.% of PAM were dispersed in DI water. Then, the mixture was rotated at 500 rpm for 10 min. A web was produced using a general wet-laid method. During this process, a drum dryer was used with a surface temperature of 140 °C and a speed of 7 m·min−1 of GN, GNO, and rGNO with a 5 g·L−1 PVDF dispersed solution of DMF. After the coating process, the fabrics were subjected to drying at 100 °C for 5 min in a drying oven. This process was repeated up to ten cycles to alter the quantity of GN coated on the MC in each case. MNNC and MGNOC were fabricated using a solvent-casting method; 5 g of PVDF, 3 g of GN, and equal amounts of PAA and LiCl (0.3 g) were stirred in a 50 mL DMF solution at room temperature for 12 h. The resultant mixture was poured into a casting plate and evaporate DMF in vacuum oven at 80 °C (pressure below 0.8 atm). Then, 100 mL of colloidal MXene solution was added and evaporation occurred under the same condition. Finally, the resultant film was separated from the casting plate.A series of GN-coated MCs were prepared by a cost-effective spray-coating process. MC was spray-coated using 3 g·LThe density was measured using a laser flash apparatus, LFA457 . A high-resolution Raman spectrophotometer Jobin Yvon, LabRam HR Evolution  was used to identify the structural features of MC, GN, GNO, rGNO, MXene, and GN-based and MXene composite. The morphologies of the fabrics were investigated using a field-emission scanning electron microscope . The X-ray diffraction patterns of the materials were recorded using a high-power X-ray diffractometer, D/max-2500V/PC  with Cu (Kα). The elemental percentages and chemical environments were analyzed using XPS with a spot-size of 30–400 µm at 100 W of Emax (Al anode) K-Alpha, Thermo Fisher . A contact angle meter, Phonix-300A , was used to analyze the wetting ability of the surfaces of the composites. A thermal analyzer, DSC TMA Q400 , was used to measure the thermogravimetric data. The EMI shielding effectiveness (SE) of the composites were recorded using an EMI shielding tent, ASTM-D4935-10, ASTM International  at room temperature (For s band). The Savitzky–Golay function  was used to plot the data. The electrical conductivities were measured using a four-probe method FPP-RS8, DASOL ENG . The thicknesses were measured using a Mitutoyo thickness 2046S dial gage . The electromagnetic characteristics of the specimens were measured using a vector network analyzer  and a rectangular wave guide with the frequency ranging from 8.2 GHz to 12.4 GHz. The samples were prepared by cutting the free-standing film into rectangular shapes (width is 22.16 mm and height is 10.16 mm) (For X band).3AlC2, Ti3C2Tx, graphene, MXene composites, and uncoated fabric (MC). Virtually the cracks and annular gaps are entailing with fiber surfaces of MC  [D/IG value of GN, GNO, rGNO were 0.14, 0.23 and 0.17, respectively (D/IG) value of 0.4, 0.84, 0.38, 0.17, 0.15 and 0.91 respectively. It was obvious that graphene coating diminished defects and films possessed less defects compare with fabric. MGNC foam consisted little high defect than MGNOC as MGNC own large hollow cavity than MGNOC  which corresponds to the band at 1578 cm−1 in the GN spectrum [−1 and 2680–2740 cm−1, respectively; these values are from the corresponding boundaries of CF crystalline graphite. In addition, the presence of HOPG is confirmed by the G-band at 1503–1634 cm−1 (−1 (2D-band), which is absent in MC. The bands in the spectrum split into a few new bands owing to the PVDF molecules [−1 and new peak at 2750 cm−1 provide evidence that the GN coating occurs on MC. In addition, the MGNC and MGNOC composites generate new peaks at 2452, 2976, and 3243 cm−1 while the G- and 2D-band intensities increase significantly. This advocates that effective interaction occurred between MXene, GN, and the polymers  . The ID/ectively . Hence, an MGNOC . Introduan MGNOC c. FurtheGNOC . The pe2 (464.5(2p1/2) and 458.5 (2p3/2) eV), Ti2+ (461.3 and 456.4 eV), and Ti-C (454.5 eV). Further, C1s displays bonds such as C–Ti–Tx (281.1 and 283.2 eV), C–C (284.5 eV), and CHx/C=O (286.1 eV) where the C–C bond gives rise to a high intense peak. The functional constitutions, namely TiO2 (529.6 eV), C–Ti–(OH)x (531.1 eV), Al2O3 (532.3 eV), and H2Oads (533.8 eV) are inveterate by the O1s fitting curve. The F1s fitting curve is purely responsible for the C–Ti–Fx bond. Hence, MXene is formed with the formula Ti3C2T [XPS is useful technique that can deliver the structural nature and functional groups of the compound analyzed; a Gaussian–Lorentzian function is used to fit the XPS data. Thus, different binding energy levels were identified by using fitted Ti2p, C1s, F1s, and O1s electron binding energy curves. In addition, the bonding nature of diverse components is reported based on the chemical shift of elements a–f 64,6,664,65. ely TiO2 9.6 eV, CT ,68. GNs −1, respectively. It is obvious that the positive wetting energy increases the hydrophilic nature. The most negative wetting energy (−42.82 mN·m−1) causes the highest contact angle and the contact angle is incommensurate with the wetting energy. The spreading coefficients of −114.65, −113.8, −115.62, −57.91, and −61.31 mN·m−1 were generated from GNMC, GNOMC, rGNOMC, MGNC, and MGNOC, respectively. The spreading coefficient also expresses a similar behavior to the wetting energy in terms of hydrophobic behavior. The rising work of adhesion increases the water-loving behavior, for instance, GNMC, GNOMC, rGNOMC, MGNC, and MGNOC engender values of 30.95, 31.8, 29.98, 87.69, and 84.28 mN·m−1, respectively; the increasing work of adhesion increases the hydrophilicity of the surface [The hydrophilicity associated with wettability plays a vital role in moistening the surfaces. A contact angle above 90° is considered hydrophobic, and below 90° is hydrophilic. Water-loving constitutions reduce the contact angle, whereas water-abhorring compounds increase the contact angle. The contact angle can be tuned by using organic or inorganic materials . The spr surface . Hence,  surface . Zhang e surface . Despite3 is the best option to tune the self-assembly of GNO flakes on the MC matrix. The conductivity is inversely proportional to the thickness [s of GNOMC are 13.68 S·cm−1 and 4.2 Ω·sq−1, respectively, at a thickness of 0.0174 cm (−1) while showing the lowest sheet resistance (3.1 Ω·sq−1) at a 0.0350 cm thickness; MGNOC exhibits 8.97 S·cm−1 with a 4.6 Ω·sq−1 sheet resistance and thickness of 0.0243 cm. Of the fabricated composite, MGNC shows a maximum thickness of 0.0350 cm, while the others, such as GNMC (0.0191 cm), GNOMC (0.0174 cm), rGNOMC (0.0163 cm), MGNMC (0.0192 cm), and MC (0.0127 cm) exhibit values below 0.0200 cm. Hence, the highest thickness of MGNC minimizes the electric conductivity. In addition, MGNMC shows the highest Rs value owing to the aggregation of the hydrophobic PVDF and hydrophilic MXene. The highest electrical mobility increases the EMI SE. Hence, the lowest sheet resistance of MGNC causes it to possess the highest surface electron mobility, which leads to the surface reflection of EMI SE [s and high resistivity of MGNC is due to the presence of MXene on the surface of the composite  and PVDF (5 g·L−1) in in a DMF solution. The thickness of MC was adjusted by changing the number of coating cycles. All of the EMI SE calculations were carried out according to the Gamage et al. study. The EMI shielding of all of the composites is illustrated in R) and absorption loss (SEA) range were 14.75–11.73 dB and 43.38–20.01 dB, respectively  and GN (3 g·L−1) in DMF, yielding 31,095.13 dB·cm2·g−1 in S band region). According to reported data, PVDF exhibits an EMI shielding effectiveness of approximately 1.1 dB, which is not an effective barrier against electromagnetic radiation compared with carbon-based PVDF composites [The mechanism of GNMC can be explained. according to structure that the MXene film and graphene nanoplates reflects incident rays caused by moving charges while internal hollow structure, free carriers and layered structure of MXene caused multiple reflection and scattering within the core, finally leads to absorption ,78. Furt·cm3·g−1 . Of the st SSE/t . Furthermposites .−3 S·cm−1 [Most of the carbon base composite reported showed lower EMI shielding compared to the composite produced and thickness proportional to EMI SE and increasing graphene loading increase the EMI SE. However, in each case, equal amount of dispersed solutions was utilized. Thus, in this case, not only component loading but also structural feature of composite affect EMI SE  77,81,8,881,82. 3 S·cm−1 . Poly  and differential thermal analysis (DTG). The temperature range was maintained from room temperature to 1000 °C with a heating rate of 10 °C·minre range a. Swift re range . In addire range . Though,re range . On the re range b. This i−3) and low thickness (0.0120–0.0350 cm). The fabricated composites exhibited an uppermost contact angle of 126° and the range of wetting energy of all of the composites was −42.82 to 14.89 mN·m−1. Thus, graphene-based constitutions improve the hydrophobicity. The surface-coated MXene and graphene oxide minimized the sheet resistance and showed a high conductivity of 13.68 S·cm−1 with a sheet resistance of 3.1 Ω·sq−1. The MXene-graphene-PVDF composition improved the thermal stability and constrained the dramatic weight changes up to 400 °C. The flat stack-like composition displayed an excellent EMI shielding of 41 dB (99.99% efficiency) in S band while exhibited maximum EMI shielding of GNMC 53.8 (99.999%) with reflection of 13.10 dB and absorption of 43.38 dB (2·g−1. Hence, the composites with high EMI SEs and that are hydrophobic in nature can be applied in various applications such as aeronautics, locators, air travel, mobile phones, handy electronics, and military application.Spray-coated composites and solvent casting films were successfully fabricated with high flexibility, low apparent density (~0.77 to 0.081 g·cm43.38 dB . and the


Inspired by the hierarchical structure and outstanding mechanical performance of biological nacre, we propose a similar multi-layered graphene–polyethylene nanocomposite as a possible lightweight material with energy-absorbing characteristics. Through coarse-grained molecular dynamics simulations, we study the mechanical performance of the nanocomposite under spall loading. Results indicate that the polymer phase can serve as a cushion upon impact, which substantially decreases maximum contact forces and thus inhibits the breakage of covalent bonds in the graphene flakes. In addition, as the overlap distance in graphene layers increases, the energy absorption capacity of the model increases. Furthermore, the polymer phase can serve as a shield upon impact to protect the graphene phase from aggregation. The dependence of mechanical response on the size of impactors is also explored. Results indicate that the maximum contact force during the impact depends on the external surface area of impactors rather than the density of impactors and that the energy absorption for all model impactors is very similar. Overall, our findings can provide a systematic understanding of the mechanical responses on graphene–polyethylene nanocomposites under spall loads. The design of lightweight materials with energy-absorbing characteristics for blast and impact applications remains a big challenge for civil, aerospace, and military applications. However, nature provides us with plenty of inspirations. For example nacre , bone 22, and wo1/2) than pure aragonite (0.25 MP·m1/2) [Nacre is also known as mother of pearl, and is a biological material with exceptional mechanical performance. Composed of 95 vol. % of layered aragonite platelets and 5 vol. % organic materials which serve as glue, nacre exhibits much higher fracture toughness (10 MPa·mMP·m1/2) . MoreoveMP·m1/2) . Both stMP·m1/2) , resultiInspired by the extraordinary strength and toughness of nacre, plenty of efforts have been devoted to synthesize similar biomimetic materials. One successful example is graphene-based artificial nacre nanocomposites. There are plenty of publications adopting this strategy to fabricate graphene-based composites which show enhanced performance in terms of Young’s modulus ,14,15,161, Im2, and Im3, are studied as shown in 1 and Im3, the atoms have the same atomic mass, which is four times of that inside the impactor Im2. To explore the dependence of impact response on the size of the graphene layers, the overlap distance As shown in 2 group in the middle or a CH3 group at the end of the polymer chain. Adjacent beads are connected by harmonic bonds. Three-body bending interactions are represented by a harmonic function of the cosine of the bond angle To improve the simulation efficiency and thus reach a relatively large temporal and spatial scale, coarse-grained models are adopted to describe the interactions for both graphene and polyethylene. The justification of the potential force field can be found in the supporting information  ensemble, where the pressure was set equal to 100 kPa. Finally, impactors were placed 10 nm above the top surface of the target, and the initial velocities of the impactors were given as 5 nm/ps. Subsequently, impactors were released and the microcanonical (NVE) ensemble was used during impact simulations.To perform coarse-grained molecular dynamics simulations, the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS)  was used1 was used. In all scenarios, the initial kinetic energy for the sample was fixed at 18.253 keV (2.92 fJ). 1) and without (S1’) polymers when the overlap distance was 24 nm. The discussion regarding temperature change can be found in the supporting information , the dynamics were similar as seen in 1, the impactor penetrated through the top layer, breaking it into two parts. Thus, from In this section, the effect of polyethylene polymers on mechanical responses is investigated during the impact simulations; for these cases, the impactor ImOLL. OL,L covered. In addition, the maximum force only fluctuates to a small extent, as the overlap distance varies for samples both with and without polymers, indicating the negligible effect of overlap distance on maximum contact forces. When the impactor hits the target with polymer, it first contacts with polymers. The polymers are compressed intensively and the velocity of the impactor is decreased. Therefore, when the impactor starts to contact with the graphene layers, the interacting forces increase moderately compared with the pure graphene sample. In contrast, for samples without polymers, the impactor directly hit the graphene layers, resulting in dramatic increase of contact forces. In 1, is smaller than that of the final state of the sample, Pe2, for all overlap distances covered. In addition, as the overlap distance increases, the maximum potential energy, both Pe1 and Pe2, increases due to the strengthening connections inside the sample. For samples without polymers, Pe1 is slightly bigger than Pe2 regardless of changing the overlap distance; for the samples with polymers, this trend is reversed. Due to the absence of polymers, the bonds of graphene flakes are more susceptible to the impact, which can be confirmed by the snapshots displayed in To verify the above conclusion, multiple simulation scenarios were considered by varying the overlap distance 5 and S5’, indicating that the forces only exist for a very short period—around 1 ps in our simulations. At the beginning, the force remains zero until the impactor hits the sample. Subsequently, the force increases intensively to the peak and then decays rapidly to zero. In addition, the maximum forces generated by impactor Im1 are smaller than those generated by impactors Im2 and Im3. Since the outer radii for impactors Im2 and Im3 are both 3.8 nm (twice that of impactor Im1), the contact areas between the impactors (Im2 and Im3) and the samples are much larger than that between the impactor (Im1) and the samples, resulting in larger contact forces. In In this section, the effect of the impactor size on the mechanical response during impact is investigated. For these impact simulations, three different impactors with the same mass are used, as shown in 2 and Im3 always remain very similar, and both are much greater than the forces caused by impactor Im1. Although the density of Im3 is much greater than that of Im2, the external (contact) surface area of these two impactors are the same, and both are greater than for impactor Im1. This leads to the differences in maximum forces shown in 2 and Im3, the maximum potential energy of the initial impact, Pe1, for impactor Im2 remains close to that for impactor Im3 as the overlap distance changes in 1 from impactor Im1 is much smaller than those for impactors Im2 and Im3. However, in the final state, the differences among scenarios using different impactors in terms of maximum potential energy Pe2 are very small, as shown in 2, has no interaction with the target, and thus the effective contact region only includes the outer region. Therefore, the effective contact region of Im2 is pretty close to that of Im3. As a result, the responses under impact are pretty close to each other for Im2 and Im3, as shown in Simulations are performed to identify the role of impactor size in the mechanical responses of samples with different overlap distance, and results are shown in In this paper, coarse-grained molecular dynamics simulations are performed to investigate the mechanical responses of graphene–polyethylene nanocomposites upon spall-like impact. Results indicate that the polymer phase can serve as a cushion upon impact, which substantially decreases maximum contact forces and thus inhibits the breakage of covalent bonds in the graphene flakes. In addition, as the overlap distance in graphene layers increases, the energy absorption capacity of the model increases. Furthermore, the polymer phase can serve as a shield upon impact to protect the graphene phase from aggregation. The dependence of mechanical response on the size of impactors is also explored. Results indicate that the maximum contact force during the impact depends on the external surface area of impactors rather than the density of impactors, and that the energy absorption for all model impactors is very similar. Overall, our findings can provide a systematic understanding of the mechanical responses on graphene–polyethylene nanocomposites under spall loads.


In recent years, many of Japanese workers have complained of fatigue and stress, considering them as risk factors for depression. Studies have found that “forest bathing” (Shinrin-yoku) has positive physiological effects, such as blood pressure reduction, improvement of autonomic and immune functions, as well as psychological effects of alleviating depression and improving mental health. In this study, we investigate the physiological and psychological effects of “forest bathing” on people of a working age with and without depressive tendencies.We conducted physiological measurements and psychological surveys before and after forest bathing with subjects who participated in day-long sessions of forest bathing, at a forest therapy base located in Hiroshima Prefecture. After excluding severely depressed individuals, the participants were classified into two groups: those with depressive tendencies (5 ≤ K6 ≤ 12) and those without depressive tendencies (K6 < 5) for comparative study. The evaluation indices measured were systolic blood pressure (SBP), diastolic blood pressure (DBP), pulse rate (PR), autonomic functions, and profile of mood states (POMS).Of the 155 participants, 37% had depressive tendencies, without any differences observed between males and females. All participants showed significant decrease in SBP, DBP, and in negative POMS items after a forest bathing session. Before the session, those with depressive tendencies scored significantly higher on the POMS negative items than those without depressive tendencies. After forest bathing, those with depressive tendencies demonstrated significantly greater improvement in many of POMS items than those without depressive tendencies, and many of them no longer differed between those with and without depressive tendencies.Examining the physiological and psychological effects of a day-long session of forest bathing on a working age group demonstrated significant positive effects on mental health, especially in those with depressive tendencies.Not applicable; this is not a report of intervention trial. In Japan, approximately 60% of workers complain about strong feelings of anxiety, worry, and stress related to work and occupation , so fatiThe effects of exposure to a forest environment include recovery from stress , and allWhile systematic review of forest therapy pointed that forest therapy may play an important role in health promotion and disease prevention, the lack of high-quality studies limits the strength of results, rendering the evidence insufficient to establish clinical practice guidelines for its use . FurtherIn this study, a group of working age people who participated in forest bathing were classified into two groups based on the presence or absence of depressive tendencies, to conduct an investigation into the physiological and psychological effects of forest bathing, and compare and examine any changes observed.In the day-long sessions of forest bathing, which were held a total of 16 times during the 3-year period from October 2012 to November 2014 at the Akiota town Forest Therapy Base in Hiroshima Prefecture, the information on forest bathing was distributed to working age people, living in the Hiroshima city areas, who mainly worked in companies. Then, 219 people applied and their written consent was acquired for this study.Inclusion criteria for the participants were working people aged between 18 and 60. Exclusion criteria were pregnant women, suspicion of severe depression (13 ≤ K6), and history of depressive and/or cardiovascular diseases. Out of the total participants, 165 participants (19–59 years old) consented to participate in this study. Ten participants who had a history of cardiovascular disease or mental illness, or who were undergoing medical treatment at the time were excluded. The rest of the 155 participants (94%) were included in the analysis. Eighty-seven of these also participated in the evaluation of autonomic nervous activity, who were assessed before and after forest therapy.The forest therapy base used for our field research is located within a national park in a valley in the region around the source of the Ota River, in the northwestern part of Hiroshima Prefecture with mountains in the 1000 m range. The vegetation mainly comprises mixed natural forests, with a temperate climate typical of the Setouchi region. The Ryuzukyo Forest Therapy Road used in this study is 3.5 km in length and 335–490 m in altitude .Figure This research was registered by the Ethics Committee of Hiroshima University (H25–29 30/04/2014).Psychological distress was measured using the Kessler Psychological Distress Scale K6 , 5, 27 wHealth-related quality of life was measured with SF-8 , which cEmotional profiles were measured with the Japanese edition of POMS . This scThe circulatory functions of systolic blood pressure (SBP), diastolic blood pressure (DBP), and pulse rate (PR) were measured using an oscillometric monitor . Autonomic nervous activities were measured using a finger-tip volumetric pulse wave meter  . Using tCirculatory function , autonomic nerve function, and POMS were examined and compared before and after the forest bathing session. Additionally, the participants were classified into two groups according to the presence or absence of depressive tendencies, and a comparison was made between the two groups before and after the forest bathing session.This study was conducted with the approval of the Department of Nursing Development Science Ethics Review Committee of the Integrated Health Sciences, Institute of Biomedical and Health Sciences at Hiroshima University . We explained that cooperation with the study was based on participants’ free will and their cooperation could be withdrawn even after consent to participate in the study had been provided. Additionally, since forest bathing is conducted in a natural environment, medical staff also participated in forest bathing session to attend to any emergency.t tests, a Wilcoxon signed rank test, a Chi-square test, a Mann–Whitney U test, simple regression analysis, and Spearman’s rank correlation coefficient were used (SPSS ver. 24). The value for significance was set at p < 0.05.The 155 participants’ circulatory function and POMS were compared and analyzed before and after a forest bathing session. Changes in autonomic functions were also compared in the 87 subjects who were measured correctly. Participants were also classified into two groups according to the presence or absence of depressive tendencies, and a comparison of the two groups was conducted. During the analysis, the correlation between SF-8 and K6, and the normality of data were confirmed using a Shapiro–Wilk test. Then, As Table The mean K6 score was 3.66 ± 3.24. Fifty-eight participants (37.4%) evinced depressive tendencies K6 of 5–12) and 97 participants (62.6%) did not demonstrate depressive tendencies (K6 of 4 or less). The mean values of K6 score for those with depressive tendencies by age were also shown in Table 2 and 97 p < 0.001) for the depressive group. There was also no significant difference between the PCS and MCS scores in the group without depressive tendencies, but the MCS score was significantly lower (p < 0.001) than the PCS score in the depressive tendencies group. The values obtained from the depressive tendencies group were significantly lower than those obtained from the group without depressive tendencies (p < 0.05 to p < 0.001) for all measures of the QOL subscales, apart from physical functioning (data was not shown).The health-related quality of life (QOL) mean SF-8 scores for all 155 participants revealed that the PCS score of 51.2 ± 4.5 was slightly higher than the average compared to the Japanese standard value of 50. On the other hand, the MCS was 47.9 ± 6.0, slightly lower than the average (Table p < 0.001) after the forest bathing. Measurements of autonomic nervous function revealed that neither parasympathetic nerve activity (ln HF) nor sympathetic nerve activity (ln LF/HF) registered any significant change.Changes in circulatory function before and after forest bathing were assessed by measuring the blood pressure of all subjects, revealing that SBP was 129.8 ± 20.4 mmHg before forest bathing and 121.5 ± 19.3 mmHg after the activity was undertaken (Table p < 0.001). However, the depressive tendencies group exhibited a significant rise (p < 0.05) in the PR after forest bathing, and this increase was notably higher than the escalation found in the without depressive tendencies group (p < 0.05). Additionally, no significant differences were found between the two groups for ln HF and ln LF/HF before and after forest bathing  (Table p < 0.001).After forest bathing, the POMS scores for all participants in the five negative subscales decreased significantly: Tension-Anxiety (T-A); Depression-Dejection (D-D); Anger-Hostility (A-H); Fatigue (F); and Confusion (C) (1) Table . Additiop < 0.05 to p < 0.001). The positive mood subscale (V) was also significantly lower in the depressive tendencies group (p = 0.001). After forest bathing, both the depressive tendencies group and the without depressive tendencies groups demonstrated a significant decrease in their scores on the negative subscales, but the degree of improvement was largest for those with depressive tendencies. In fact, after forest bathing, the multiple negative scales  for the depressive tendencies group decreased to levels equal to those recorded by the without depressive tendencies group, to the extent that any significant difference between the groups disappeared. Meanwhile, TMD measurements revealed that negative mood states were significantly greater (p < 0.001) before forest bathing in the depressive tendencies group than in the without depressive tendencies group, and this score decreased significantly after forest bathing. Additionally, the degree of modification in the POMS scales before and after forest bathing was computed as T-A (− 8.97), D-D (− 7.16), A-H (− 7.40), F (− 5.88), and C (− 6.41) for the depressive tendencies group; and T-A (− 5.03), D-D (− 4.09), A-H (− 3.56), F (− 1.03), and C (− 3.40) for the without depressive tendencies group. Thus, the changes observed in the depressive tendencies group were significantly larger than those witnessed in the without depressive tendencies group (p < 0.05 to p < 0.001) .When comparing the depressive tendencies group and the without depressive tendencies group, the former evinced significantly higher negative mood subscales  before forest bathing than the latter (01) Fig. . The TMDOf the 155 participants in this study, 37% presented with depressive tendencies (K6 of 5–12 inclusive), with the greatest number among younger and middle-aged people. For health-related QOL (SF-8), the PCS was close to the average (50 points), but the MCS was below average. According to the results of the WHO’s World Mental Health survey, and the World Mental Health Japan Survey, one in four people reported that they had experienced some kind of mental health problem in their lifetime , 28. TheSBP and DBP of the participants showed a significant decrease as a result of the forest bathing for about 2 h. However, no change was observed in PR, HF, and LF/HF, which are indicators of autonomic nervous activities. This contrasts with an observational study that was conducted over 2 days in several forest regions throughout Japan , 19. ThiFurthermore, no significant difference in circulatory function and autonomic nervous function was observed before forest bathing between participants with and without depressive tendencies. Both SBP and DBP showed a significant decrease in both groups after forest bathing, and only those with depressive tendencies showed a significant rise in PR. Other studies have found that those with depressive tendencies are less active in their daily lives and that they engage in fewer leisure activities . This laChanges in psychological indicators (POMS), including the negative mood states  and TMD scores were significantly improved for all participants following forest bathing. However, no alteration to the positive mood state (V) was observed. On this issue, studies of short-term walking over a period of 2 days and one night conducted in multiple areas took measurements when participants were walking or engaging in seated viewing , 21. TheIn this study, significant changes in psychological indicators were greater in those with depressed tendencies than in those without depressive tendencies. Correspondingly, the improvement recorded after forest bathing was also greater for the depressive tendencies group, to the extent that after forest bathing, there was no significant difference in negative mood state values recorded for the two groups.t values of the negative scales. Studies have found that individuals with high blood pressure or high stress levels are more likely to exhibit improvement after forest bathing than healthy individuals [The POMS values before and after forest bathing were individually examined, as were the K6 scores, and the relationship between changes recorded before and after forest bathing. Figure ividuals , 34. In ividuals  and posiividuals  study ofividuals  and Yoshividuals  reportedividuals . In the ividuals , and impividuals .Fig. 3CoPrevious study also reported that psychological and social stimulation occurs through interaction with the environment , 42. ParHowever, it is possible that “regression to the mean” have influenced the results of this study demonstrating significantly greater improvement in many of POMS score for those with depressive tendencies. It is important that the improvement in POMS score for those with depressive tendencies was much greater than for the non-depressive tendencies after forest bathing, and that no more significant differences were identified in many of POMS scores between the two groups. Hence, we think that it is difficult to explain the greater improvement of POMS score in depressive tendencies simply by “regression to the mean.”Moreover, as we did not measure sex hormones in this study, we cannot discuss the influence of the menstrual cycle of the female subjects. However, there is no difference in the ratio of males and females among the two groups. Additionally, the menstrual cycle is randomly assigned to the two groups, and no intentional bias is recognized. As this study focused on short-term changes such as examining physiological and psychological changes before and after forest bathing for individuals, it is considered that sex hormones may have little influence on the results of this study.In this study, the improvement of mental health was statistically significant, especially in the participants with depressive tendencies. Changes were sufficiently large to be clinically meaningful. However, it will be necessary to conduct further studies to validate the efficacy of forest bathing for working age people with depressive tendencies, since other outcomes, such as autonomic functions, did not change significantly. Additionally, this study was limited to results obtained from a single day’s activity over about 2 h, and, thus, can only confirm a short-term effect. The study was also limited by the paucity of cross-sectional research to corroborate its effects. Moving forward, a more detailed examination of the beneficial health effects of forest bathing is required, through the establishment of control groups and the implementation of overnight forest bathing sessions.The results of this study suggest that a session of approximately 2 h of forest bathing as part of a 1-day outing in a forest environment can lead to improvements in physiological and psychological health in people of working age, as demonstrated by the decrease in blood pressure and the alleviation of negative psychological parameters after forest bathing.Moreover, participants with depressive tendencies showed a greater improvement in many of the POMS items after forest bathing compared to those who did not display depressive tendencies. This outcome is evidence that a 1-day forest bathing activity was particularly effective at enhancing the psychological wellbeing of working age people with depressive tendencies.


Undisturbed flows are critical in these systems, and air bubbles entering microfluidic channels can lead to device delamination or cell damage. To prevent bubble entry into microfluidic channels, we report a low-cost, Rapidly Integrated Debubbler (RID) module that is simple to fabricate, inexpensive, and easily combined with existing experimental systems. We demonstrate successful removal of air bubbles spanning three orders of magnitude with a maximum removal rate (dV/dt) In the 1990s microfluidic systems gained popularity in analytical “lab-on-a-chip” platforms owing to unique microscale capabilities including robust sample routing, rapid multiplexed analysis, and laboratory portability . Over thmax ranging from 0.5 μL min−1 to > 2 mL min−1.Bubble removal can be divided into two general approaches, (i) bubble traps and (ii) debubblers. Traps focus on guiding bubbles to a containment reservoir before they enter the cell culture region; traps leverage the buoyancy of air bubbles and can be vented with an external vacuum source as the reservoir capacity is reached ,13,14. DAlthough myriad debubblers have been reported in the literature, they are often complex and highly application-specific; thus, integration into more general microfluidic systems represents a significant implementation barrier. To address hurdles related to both complex fabrication and integration of debubblers, we introduce a simple workflow to create a rapidly integrated debubbler (RID) module that can be easily combined with existing microfluidic systems. Key practical features of the RID module include (i) an accessible fabrication process with rapid assembly (<2 min), (ii) low device cost (<$0.50 at lab prototype level), and (iii) press-to-fit tubing connections to simplify component integration. Controlled shear stimulation of cultured cells is a hallmark capability in microfluidic systems that enables quantitative correlation between applied fluid-induced wall shear stresses (WSS) and cellular responses including endothelial cell alignment , calcium2 laser  with inlet and outlet ports in L1 designed to house #003 rubber O-rings (outer diameter (OD) = 3/16”, inner diameter (ID) = 1/16”, Durometer 70A, McMaster-Carr). Pressure sensitive adhesive films  were rolled onto the top surfaces of L1–L2 prior to laser cutting using a cold roll laminator. A polytetrafluoroethylene (PTFE) membrane  was cut with a razor blade and placed in contact with L3. L3 (PMMA) was used to protect the PTFE membrane from damage due to improper insertion of the tubing. The 2 mm wide by 12 mm region cut into L5 (polyester film with PSA on bottom surface) defined the degassing region of the device, and the PSA lamination produced liquid-tight sealing between layers. Once all layers were cut in a batch process, individual devices could be assembled in less than 2 min. The packed O-ring assembly allowed simple press-to-fit connection with 1/16” OD tubing, and the addition of barbed end fittings  allowed attachment to flexible tubing. The overall footprint of the RID module was 10 mm × 18.5 mm (W × L). As shown in total minimization as the vapor (v) phase  and liquid (l) phase interact with the solid components of the PTFE membrane. The change in total surface energy, ΔEtotal, can be expressed as the change in interfacial area, ΔA, during the attachment of vapor to the membrane, and the difference in surface energy (γ) between the solid-vapor (sv) and solid-liquid (sl) interfaces [The operating principle of the RID module is based on total surface energy Eterfaces : (1)ΔEtosl to the interfacial energies: The Young equation relates the solid-liquid contact angle θsl > 90°) the right-hand side of Equation (2) is negative implying that γsv < γsl; from Equation (1), there is a corresponding energetically favorable decrease in total surface energy. Conversely, for a hydrophilic material (θsl < 90°), γsv > γsl with unfavorable ΔEtotal > 0. Thus, the hydrophobic PTFE membrane used in the RID module energetically favors the formation of vapor-solid interfaces when compared with a hydrophilic material.With a hydrophobic material,  or by decreasing the pore size (Equation (3)). At P > Pb, and (iii) Vb:VT ratio . A test condition failed when a bubble was visualized in the fluid exiting the device via image analysis. We conservatively report the failure threshold as the lower bound of the 95% confidence interval determined from failure testing of four independent RID devices. The equation WSS = 6 μQw–1 h–2  [channel = 1 μL). To characterize RID bubble removal, individual streams of air and liquid  were combined to create segmented flow streams and directed toward the input port of the RID. The test liquid was complete cell culture media Dulbecco’s Modified Eagle Medium /F-12  with food color added to increase contrast during imaging. Flow streams entering and exiting the RID module were simultaneously recorded  and analyzed with a custom MATLAB image processing script see . Black a h << w)  was usedopen. Results reported as mean ± standard deviation (SD) from four independent devices.A 5 mL fluid reservoir was connected vertically to the input of the debubbler. With the debubbler dry, cell culture media was added to the reservoir to generate a hydrostatic pressure head ΔP = ρgΔh with Δh denoting the difference in height between the media level and the outlet port. Using video analysis, the height difference required to initiate flow through the debubbler was determined and converted to the opening pressure Pcritical at which fluid was forced through the PTFE membrane. Results reported as mean ± SD from four independent devices. A syringe pump was used to introduce cell culture medium to the RID, while the outlet port was connected to dead-end tubing. Sensors on either side of the debubbler  measured the pressure across the module as a function of time. Video analysis was used to determine the critical liquid pressure PA glass capillary viscometer was used to measure the viscosity of DMEM/F12 cell culture media with 10% FBS. Fluid density was determined by measuring mass of a known media volume using an analytical balance  at 37 °C. A goniometer  was used to measure the interfacial tension of cell culture media in air, and the contact angle between the culture medium and PTFE membrane using the hanging drop and sessile drop methods respectively. Results reported as mean ± SD from four independent devices. –2 on Geltrex coated tissue culture flasks. Media was replaced every 24–48 h. For routine culture, human umbilical vein endothelial cells (HUVEC) were cultured in DMEM/F12 with 10% v/v FBS using the manufacturer’s protocols. Briefly, HUVECs were enzymatically disassociated using Trypsin/EDTA  and sub-cultured when they reached 70% confluence. Cells were centrifuged at 250 g, resuspended in medium, and counted. Cells were plated at 5000–10,000 cells cm−1) at 37 °C for 1 h to improve cell adhesion. Excess Geltrex solution was aspirated, and a PDMS microfluidic network was magnetically sealed against the glass substrate. The microfluidic channel network was fabricated using a soft lithography process described previously [−2 and allowed to attach overnight. Cells were then treated with Calcein AM  and the cell permeable Hoechst 33342 stain  for 15 min to aid visualization of HUVEC cytoplasm and nuclei respectively. HUVECs in culture were imaged after exposure to a segmented air-liquid stream with flow rate corresponding to WSS of 11.5 dyne cm−2 with and without a RID module upstream of the culture device. The RID modules were sterilized with ethanol followed by 3× wash with PBS to remove residual ethanol and allowed to dry before use. For bubble exposure studies, a microfluidic channel network was sealed against a glass slide using our previously reported reversibly Sealed, Easy Access, Modular (SEAM) culture platform ,25. Glaseviously . HUVECs −2) [−2) [channel = 1 μL. The range of tested bubble volumes was selected to evaluate bubble removal capabilities under common flow disruption scenarios: (i) Vb < Vchannel, (ii) Vb ≥ Vchannel, and (iii) Vb >> Vchannel . A custom image processing algorithm was used to measure Vb, Vb:VT, and Q. Results from the RID bubble removal testing are summarized in To ensure that RID modules could be used for shear stimulation studies relevant to human (1–50 dyne cm−2)  and rode−2) [−2) , segmentb ≤ 100 μL) from segmented flows (0.07 ≤ Vb:VT ≤ 0.7) including the challenging high Q (high WSS), small Vb, and high Vb:VT conditions where dV/dt must be sufficiently high to remove bubbles before they are displaced downstream by the incoming flow. The average WSS at failure = 289 ± 48 dyne cm−2 with 95% confidence interval, 213 < WSS < 352 dyne cm−2; the dashed line in −2 or Q = 2.6 mL min−1), and represents a conservative limit of the operational range. Although the 95% confidence interval is relatively large, the RID reproducibly removed large and small volume bubbles at flow rates corresponding to WSS that span the physiological ranges of both human and rodent cells commonly used to study shear stimulation in vitro. RID (dV/dt)max = 1.5 mL min−1, enables rapid removal of bubbles, and is competitive with more complex and specialized debubblers. Traditionally, debubblers are designed for a particular bubble removal operation range; to the best of our knowledge, this is the first demonstration of a rapid debubbler spanning at least three orders of magnitude in removed Vb with a single device. It should be noted that Vb = 100 μL was the maximum bubble volume tested due to experimental limitations and was not the operational failure limit of the RID. Although bubbles with Vb < 200 nL could not be reproducibly generated using our experimental setup, we anticipate that smaller volume bubbles would be removed either at (i) the entrance of the RID module via contact with the PTFE membrane due to the perpendicular orientation of the input tubing or (ii) in the gap between the membrane and PMMA where the bubble interactions with the membrane are energetically favorable. The RID successfully removed bubbles across three orders of magnitude  at Q = 1.1 mL min−1 (liquid WSS = 90 dyne cm−2); flow direction is left to right. Bubbles entering the RID module were removed with dV/dt = 440 μL min−1 and single-phase flow exited the device  was maintained for both experimental conditions. −1 h−2. Under the test conditions, we estimate the amplification factor Φ comparing WSS with and without bubbles  = 55 , we measured (i) the minimum pressure, Popen, required to deflect the PTFE membrane from the PMMA layer and (ii) the maximum pressure, Pcritical, above which cell culture media was forced through the hydrophobic PTFE membrane pores. The operating pressure range spanned three orders of magnitude with Popen = 7.4 ± 0.4 Pa and Pcritical = 9.7 ± 1.7 kPa. The small opening pressure can be attributed to the limited adhesion between the hydrophobic PTFE and the PMMA surface that must be overcome by the flow stream pressure. Pcritical is a function of membrane pore diameter; the manufacturer’s reported PTFE pore diameter of 10 μm was sufficient for our applications. However, a membrane with a smaller pore size can be used if a higher Pcritical is desired (see Equation (3)). It should be noted that the PTFE membranes do not contain well-defined circular pores but are comprised of a fibrous mesh that contain voids between fibers; the relatively large 95% CI for WSS at failure can be attributed in part to inhomogeneities between membranes. To determine the operating pressure range for the RID . The interconnection problem can be a source of frustration because each component can have different tubing requirements and corresponding mating mechanisms . A goal of this work was to increase accessibility by providing an integration approach to simplify connections. Here, we implemented a simple connection mechanism via embedded O-rings in the top housing layer of the RID module that form a compression seal against inserted rigid tubing. The press-to-fit O-ring connectors See  were ablTo facilitate customization and improve debubbler accessibility for the microfluidics community, the RID fabrication workflow uses equipment commonly found in a community makerspace or general research laboratory. Our approach incorporates commercially available materials , and modules can be assembled in less than 2 min when layers  are cut We have demonstrated a simple fabrication workflow to create a debubbler that can rapidly remove bubble volumes spanning three orders of magnitude from segmented flows at flow rates compatible with those required for microfluidic shear stimulation studies. The fabrication process can be carried out in a general makerspace or research laboratory and the footprint and fluidic interconnections can be customized as needed to fit existing experimental setups. We anticipate that the combination of simple fabrication, integration, and functional capabilities will enable RIDs to be easily implemented into microfluidic applications where the entry of bubbles is undesired.


Our results revealed that the veterans with sarcoidosis significantly differed from civilians, according to metabolic and metallomics profiles. Moreover, the results showed that veterans with sarcoidosis and veterans with COPD were similar to each other in metabolomics and metallomics profiles. This study suggests the important role of environmental risk factors in the development of different molecular phenotypic responses of sarcoidosis. In addition, this study suggests that sarcoidosis in veterans may be an occupational disease.Sarcoidosis is a disorder characterized by granulomatous inflammation of unclear etiology. In this study we evaluated whether veterans with sarcoidosis exhibited different plasma metabolomic and metallomic profiles compared with civilians with sarcoidosis. A case control study was performed on veteran and civilian patients with confirmed sarcoidosis. Proton nuclear magnetic resonance spectroscopy ( Although not well studied, the incidence of sarcoidosis among veterans is estimated to be even higher2. Sarcoidosis has protean manifestations including ophthalmic, joint, skin, and liver involvements, but most often involves the lung, affecting almost 90% of cases. In some individuals it can lead to serious disability of affected organs such as pulmonary fibrosis, cirrhosis, blindness, and may be fatal. Unfortunately, there is no available noninvasive biomarker to facilitate the diagnosis nor predict progression of disease.Sarcoidosis is a granulomatous entity of unknown etiology. The incidence of sarcoidosis has been well studied in the American civilian population and ranges between 11 in 100,000 in Caucasians to up to 36 in 100,000 in African American populations4. Two of the more commonly used analytical platforms for metabolomics studies are proton nuclear magnetic resonance (1H-NMR) spectroscopy, a very robust and consistent method, and hydrophilic interaction liquid chromatography mass spectrometry (HILIC-MS), an extremely sensitive method5. Metabolomics has helped to identify potential biomarkers for the diagnosis and prognosis of infectious and non-infectious respiratory conditions such as asthma6, chronic obstructive pulmonary disease (COPD)8, influenza9, pneumonia10, tuberculosis11, and acute respiratory distress syndrome (ARDS)13.Metabolomics is a method to identify and measure small molecules – metabolites – which may provide a way to study and monitor disease progression. In addition, has the potential to differentiate various stages of a particular disorder, provide means for a more accurate diagnosis and possibly stratification of prognosis14. Inductively coupled plasma-mass spectrometry (ICP-MS) is a highly sensitive technique used to detect and quantify elements in the periodic table in biological fluids15.Metallomics targets various elements and metal ions that participate in many biological pathways in close relationship with proteins and metabolites16. Because of this, we sought to evaluate whether veterans with sarcoidosis exhibit different metabolomics and metallomics profiles compared with civilians with sarcoidosis. Furthermore, we evaluated whether veterans with sarcoidosis have a different metabolomic and metallomic profile compared to other veterans with a non-sarcoidosis pulmonary condition, (COPD).The veteran population comprise a particular group of subjects with a unique history of exposure to hazardous materials, including gun smoke, jet fuel, air pollution  and occupational hazards We performed a case-control study on veterans (n = 13) and civilians (n = 30) with confirmed pulmonary sarcoidosis. Sarcoidosis was defined as the presence of clinical signs and symptoms of pulmonary sarcoidosis or the presence or history of bilateral hilar lymphadenopathy, along with biopsy-proven sarcoid-like granulomas in pulmonary samples, with the exclusion of other granulomatous conditions, including mycobacterial infection.Airflow obstruction was defined per American Thoracic Society and European Respiratory Society (ATS/ERS) guidelines with an FEV1/FVC ratio less than lower limit of normal (24). In order to further analyze the metabolomic profiles of veterans without sarcoidosis and with similar exposure history, we randomly selected 35 veterans with COPD as controls, matched by race, gender, and deployment history. Civilians were recruited from the University of Miami Sarcoidosis Program and veterans from the Miami Veterans Administration Sarcoidosis Program.This retrospective study was conducted in accordance with Helsinki Declaration and the study was been approved by the University of Miami’s Institutional Review Board (No.20150612). Written informed consent was obtained from all participants.1H-NMR spectroscopy. Details of sample preparation have been described in the Supplementary Appendix . Details of the 1H-NMR analysis have previously published9 and provided in the Supp. 17.Plasma samples were obtained from all patients and analyzed by Plasma samples were also analyzed by liquid chromatography mass spectroscopy (LC-MS) using the Q Exactive HF Hybrid Quadrupole-Orbitrap Mass Spectrometer, Thermo-Fisher). Chromatography was performed using a 2.1 mm × 100 mm long Syncronis HILIC (thermos-Fisher) LC column packed in-house with 3 µm porous Hypercarb particles.2O). MS conditions were as follows: HESI-II temperature 325 °C, auxiliary gas flow 10 units, sheath gas flow 25, spray voltage ± 2.50 kV, capillary temperature 275 °C, and S-lens RF level 60%, auxiliary gas heater temperature 275 °C for negative ion mode. To acquire mass spectra, mass scan parameters were set up as follows: runtime 20 mins, full MS scan type, resolution 240,000, AGC target 3e6, maximum IT 200 ms and scan range 70–1000 m/z. Maven software, an open source software, was used for processing metabolomics data obtained by LC-MS18.The elution gradient of solvent B (%) (acetonitrile with 0.1% formic acid) over time was: 95% for 2 min, 85%–95% for 5 min, 5–80% for 3 min, and 5% for 5 min, 5–95% for 2 min and then held at 95% for last 3 min against solvent A  mode was applied for analysis of plasma using a single continuous method. To attenuate all polyatomic interference, hydrogen gas was added to the iCRC skimmer. Both iCRC and non-iCRC modes were applied for analysis, thus the isotopes (different forms of an element with ‘different number of neutrons) 51V, 75As, 78Se and 90Zr were quantified by both iCRC mode and non-iCRC mode. 24Mg, 56Fe and 51Cr were quantified only in iCRC mode and non-iCRC mode was used for all the remaining isotopes.The plasma metallome was assessed using inductively coupled plasma mass spectrometry (ICP-MS). Details of the sample preparation is also described in the Supp. 19 and MetaBox20 were used for univariate data analyses. Data were not preprocessed for the univariate analyses.Both univariate and multivariate data analyses were applied to the extracted information from the metabolomic datasets. Univariate analyses such as, ANOVA and T-test were used as complementary methods to the multivariate analysis in order to provide useful information on metabolomics profiles and on metabolite individually. MetaboAnalystMultivariate data analysis was applied to reduce the complexity of metabolomics data and for data mining. Principal component analysis (PCA) was performed to find outliers, trends, and similarities, using datasets derived from the plasma samples for the evaluation of interrelations and groupings of metabolomics data between veteran and civilians with pulmonary sarcoidosis and veterans with COPD.2Y  and cross validation ANOVA (CV-ANOVA) parameters were considered for predictability and significance of separation of study populations using metabolomics profiles22. Q2Y > 0.3 and 0.5 were evaluated as acceptable and good models for human samples. P value ≤ 0.05 was considered a significant model. The highest Q2Y was considered in choosing the OPLS-DA model. S-plot and coefficient plot were applied to find the most significant metabolites that contributed to the separation as potential variables in the study. S-plot was used to extract the putative biomarkers, that have both high reliability and magnitude. Compounds with covariance >0.1 were considered important metabolites23. SIMCA-P v15.0.2  and MetaboAnalyst 3.0 software were used for multivariate analyses. Data were normalized (median), transformed (log) and auto-scaled for multivariate analyses.Partial least square-discriminant analysis (PLS-DA) and orthogonal partial least square-discriminant analysis (OPLS-DA) are two supervised multivariate data analyses methods for classification and discrimination between groups by maximizing separation using most differentiating variables responsible for class discriminations. PLS-Da and OPLS-DA were used to separate different populations and to establish metabolomic profiles for each population based on the most differentiating metabolites. QPrediction test was used to obtain sensitivity, specificity and area under the curve for receiver operating (AUROC) parameters. The prediction test was carried out by splitting the population of the study into a training and a predicting set. The predicting group was created by randomly selecting 25% of the samples. A misclassification table was obtained for all discriminant analysis models to measure sensitivity and specificity using SIMCA-P v15.0.2 software. AUROC was calculated using Graph Pad Prism v 3.03.24, a free web-based tool, and Cytoscape 3.6.025 using selected discriminative metabolites in the separation of veteran sarcoidosis from civilian cohorts. Reactome, an open-source, open access, pathway database was also used to explore biochemical networks26. The list of discriminative metabolites was chosen according to the best OPLS-DA model which had higher predictability (Q2Y).Parallel pathway analyses were performed using MetaboAnalyst 3.0Of the 78 subjects who were consented for the study, 43 had sarcoidosis (13 veterans and 30 civilians) and 35 were veterans with COPD. Demographic characteristics are summarized in Table Among COPD subjects, the mean (SD) age was 63.5 (4.7), which was significantly older than veterans with sarcoidosis (P = 0.038). However, there was no difference in race and gender between these two groups.1H-NMR Suite 7.127, one dimensional 1H-NMR analysis resulted in the identification of 55 metabolites including sugars, organic acids, amino acids, and volatile organic compounds. Using the Maven software, 103 variables were identified in a targeted approach to the HILIC-MS analysis and consisted of sugars, amino acids, organic acids, acylcarnitines and their derivatives.Using ChenomX 1H-NMR and HILIC-MS, respectively  than 1H-NMR spectroscopy   Fig. . Forty-o−5) Fig. . Six met2Y) using a variable importance in projection (VIP) approach. S-plot revealed that taurine, sucrose, n-methyl-d-aspartic acid, ll-2–6-diaminoheptanedioate, hypoxanthine, ethanolamine, alpha-hydroxyisobutyric acid, sn-glycerol 3-phosphate, 2-oxoisocaporate, 4-hydroxybutyrate, acetone histidine, isoleucine, isopropanol, methionine and beta-alanine were the most plausible biomarkers to differentiate between the two sarcoidosis cohorts in both datasets  using 200 repetitions  different between the veteran and civilian cohorts with 6 having a significant low false discovery rates (FDR) (<0.05) (Table Unpaired T-tests on the sarcoidosis populations were performed using 55 and 103 metabolites identified by 5) Table  & Fig. 25) Table  & Fig. 32 = 0.724) and 1H-NMR (Q2 = 0.713)  and significant difference (p = 0.00012 and 0.0001) for both 1H-NMR and HILIC-MS methods were considerably lower between the two veteran cohorts  Figs. . HoweverIn a targeted approach, 33 trace elements were quantified in the plasma samples of the three cohorts  using ICP-MS techniques. PCA analysis Fig  shows a 2Y = 0.688) and significant (p = 6.003 × 10−6) model to discriminate between the two sarcoidosis groups based on the 33 elements , gallium (71Ga), nickel (60Ni), cesium (133Cs), arsenic (75As), barium (137Ba), aluminum (127Al) and mercury (202Hg) and decreased boron (11Ba), antimony (121Sb), cadmium (114Cd) bromine (79Br), cobalt (59Co), Calcium (44Ca), selenium (77Se), strontium (88Sr), palladium (105Pd), magnesium (24Mg) and lead (208Pb) in the plasma samples of the veterans with sarcoidosis compared to the civilian cohort. Unpaired t-test, a univariate approach, showed 18 elements that were significantly different (p < 0.05) between the two sarcoidosis groups, including 10 elements with significant FDR (<0.05) (Table 56Fe) and manganese (55Mn) were significantly increased in the plasma of veteran sarcoidosis compared to civilian cohort. Permutation test confirmed the validation of R2 and Q2 values of each predictive model (OPLS-DA) using 200 repetitions.OPLS-DA analysis revealed a very good, highly predictive  Table . It has 2Y = 0.81) in separating civilian sarcoidosis subjects from veterans with COPD, while it was a less predictive discriminant model (Q2Y = 0.53) in separating veteran sarcoidosis subjects from veterans with COPD, using 29 elements . R2 values for the regression were obtained using the PLSR method based on the most important metabolites obtained by the OPLS-DA analysis. Moreover, logistic regression showed that CPI is not a good predictive marker to discriminate between the two sarcoidosis cohorts  than metabolomics in discriminating between the sarcoidosis cohorts   with a high degree of predictability and a statistic significant difference (Q19) Fig. .Figure 51H-NMR and HILIC-MS metabolomics datasets were further integrated using a normalized and block scaled method. Although there were several overlapped metabolites, both methods used different approaches for metabolite identification. The OPLS-DA model obtained, showed a slight improvement in separating the two sarcoidosis cohorts (Q2Y = 0.626) based on the 72 metabolites compared to the HILIC-MS dataset alone. Similar results were obtained for the discrimination between veterans with sarcoidosis and COPD, with a Q2Y = 0.693 and Q2Y = 0.843, respectively. Therefore, the combination of the two datasets further illustrates the metabolomic similarity of the two veteran cohorts when compared with the civilian sarcoidosis group.The 1H-NMR platforms. Table 1H-NMR and HILIC-MS datasets is shown in the supplementary section.  triggers that may have their own particular pathophysiologic signature. Not surprisingly, the metabolic profiles among the two veteran cohorts studied (sarcoidosis and COPD) showed more similarity between them compared to civilians with sarcoidosis.31, but to the best of our knowledge, no study has experimentally demonstrated this relation clearly when related to environmental exposure and sarcoidosis. The application of metabolomics in studying sarcoidosis has been reported previously. Lactate, acetate and N-butyrate is increased in saliva and 3-hydroxybutyrate, acetoacetate, carnitine, cystine, homocysteine, pyruvate, and trimethylamine N-oxide are some metabolites increased in the serum samples of patients with sarcoidosis compared to normal controls, while serum methanol, butyrate in saliva and isoleucine, glutamine and succinate are decreased33. We previously showed LC-MS-based metabolomics could differentiate fibrosing from non-fibrosing pulmonary sarcoidosis as well as differentiate subjects with composite phycological index (CPI) > 40 versus those that had CPI < 4034.A number of reviews and research studies have addressed the impact of “exposomes” in altering metabolomics signatures and the role of metabolomics in characterizing particular environmental factors1H-NMR and HILIC-MS detection methods, but most notably by the latter. Veterans with sarcoidosis have unique exposures and this may dictate the development of a particular type of sarcoidosis. For example, Gulf War Illness (GWI) is a syndrome described in deployed military to the Persian Gulf region exposed to particular environmental threats such as dust storms35. It is a multisystem disease diagnosed based on the Kansas criteria 35. Targeted metabolomics studies have shown GWI is a unique metabolic syndrome that is characterized with increased sphingolipids and phosphatidylcholines and decreased purines and endocannabinoids36, a specific metabolic fingerprint different to other conditions with similar symptomatology such as myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS)36. Furthermore, the lipid profile of GWI can be replicated in rat and mouse models exposed to a nerve gas antidote, pyridostigmine bromide38. On the other hand, mounting evidence has indicated that environmental exposure such airborne inorganic dust could be risk factors for sarcoidosis39 and that the nature of the exposure can impact the frequency and clinical phenotypes of the disease40. In mouse models, exposure to silica dust leads to metabolomic alterations after lung inflammation41. Similarly, we present here significant differences in metabolomic profiles in 2 sarcoidosis populations with different exposures.In this study we used metabolomics as a tool to characterize the exposome and investigate the molecular fingerprints and key cellular processes that are likely activated by exposure to the environment. The differences in metabolite alterations were readily detectable by both 43. Amino acids such as glutamine, phenylalanine, tryptophan, arginine and cysteine play a vital role in immunomodulation, particularly through the T-cell proliferation and activation44. Veterans also exhibited an increased concentration in some anti-inflammatory biomarkers such as taurine, hypoxanthine, glucosamine, reflecting a high degree of interactions between both anti-inflammatory and pro-inflammation mechanisms.One of the significant metabolomic changes observed was in amino acids. Compared to civilians, veterans with sarcoidosis exhibited lower concentration in most amino acids analyzed molecules important in the induction of anti-inflammatory mechanisms and reducing stress response in inflammation46. For example, exposure to beryllium, aluminum, rare earth elements, and titanium have been associated with sarcoidosis in mine, manufacturer, and agriculture workers49. We found significantly higher in the plasma concentration of rubidium, gallium, nickel, and cesium in the plasma of veterans compared to civilians with sarcoidosis. Veterans deployed to the Middle East have particular exposures to heavy metal and trace elements. For example, Pb, Zn, Cd, Ni, and Cr contamination of seawater, food, and soils due to the Gulf War and oil spills have been reported51. Military operations by themselves have added another potential source of contamination of water and soil in the gulf, During the two Gulf Wars in the 1990s, millions of hectares were contaminated due to spilling of millions of oil barrels and burning of hundreds of oil wells and is estimated that 340 tons of uranium was depleted in the first Gulf War52. Accordingly, we have shown that the plasma level of uranium in veterans with sarcoidosis is higher than was observed in the civilian cohort. Furthermore, nickel contamination from different sources such as batteries can have effect on lung and antioxidant system in the form of water-soluble nickel phosphate53. Nickel was also higher in the veteran sarcoidosis group.Exposure to metallic environmental factors, including occupational and infectious causes, have been associated with sarcoidosis54. Metalloids become localized and interact with pulmonary cells and tissues or are dispersed all over the body by passing biological barriers55. Metal ions have significant biological effects in different metabolic pathways57. For example, radioactive Cesium 137 (137Cs) has been associated with reduced lung function in children in the Chernobyl disaster58.The lung is the first line of exposure that is exposed to essential or non-essential/toxic elements and potentially toxic metal-related nanomaterials. Nanoparticles generated from dust storms or gun powders may deposit in the lungs and direct activated alveolar macrophages toward the pulmonary interstitium causing a more severe immune response than larger particles60. The association of silica exposure and development of sarcoidosis was studied by Rafnsson et al.61, who found that people who were exposed to dust had up to a 5 times higher risk of development of pulmonary sarcoidosis when compared to a normal population . Dust storms also contain particles such as, calcium oxide (CaO) and magnesium oxide (MgO), and oxides of sodium and potassium (Na2O and K2O) as well as silicon dioxide (SiO2), aluminum oxide (Al2O3), iron (Fe2O3) and titanium (TiO2) oxides and trace elements such as, zirconium (Zr), strontium (Sr), rubidium (Rb)62. Our data showed that Mg, Ca, Al, Ti, and Fe is increased in veterans with sarcoidosis compared to the civilian sarcoidosis population. Investigations on dust in the Iraq desert revealed that the quartz particle is surrounded by calcium carbonate containing various elements such as aluminum, iron, uranium, nickel, cobalt, copper, lead, chromium, strontium, tin, manganese, zinc, barium, arsenic, and vanadium63. Accordingly, we observed an increase in most of the aforementioned elements in the plasma samples of veteran sarcoidosis. Of note, cadmium, known to be involved in the pathogenesis of pulmonary carcinogenesis64, was not higher among the veterans studied.Dust storms in deployment areas represent an additional exposure hazard due to their high contents of silica, aluminum, and rare earth elements66. This substitution can alter the function of annexin A11 (ANXA11), an intracellular metalloprotein that carries 5 calcium ions. It has been proposed that alteration of ANXA11 is associated with pulmonary fibrosis in sarcoidosis67. In this way, sarcoidosis in veterans may be considered an occupational disease.We also noted that veterans with sarcoidosis have higher concentrations of elements that regulate biologic processes in immune cells. For instance, lanthanum (a rare earth element) can compete with calcium in different proteins68.Another interesting finding noted in veterans with sarcoidosis was with pathway analysis, which showed that GABA synthesis and metabolism might be downregulated in veterans compared to civilian with sarcoidosis, with both precursor metabolites of GABA (glutamate or glutamine) and breakdown metabolites of GABA  were decrease in veterans. GABA can modulate the immune response via secretion of cytokines, activation, proliferation and migration of immune cells1H-NMR, HILIC-MS and ICP-MS, serves as an important internal validation of our results.The current study has two major limitations. A relatively low sample size in our study may lead to a lack of precision and the results have not been validated in an external validation cohort. To partially overcome the limitations, we applied 3 different methods to validate the findings with higher resolution. The very similar results obtained using three different techniques, Using metabolomics and metallomics, this study provides relevant evidence for the role of potential environmental risk factors for different molecular phenotypic responses of sarcoidosis. More investigation will be needed to identify biochemical pathways that link between environmental risk factors and a disease phenotype as well as metal-related metabolomics perturbations in human diseases. We conclude then that this comprehensive metabolite and metallomic profiling clearly shows distinct metabolomic profiles between two sarcoidosis populations exposed to different environmental factors. Metabolic fingerprints can be a powerful and useful tool for sarcoidosis phenotyping in a more accurate manner than the current clinical approach. Furthermore, characterization of metabolic profiles is a promising platform to better understand the underlying pathophysiological mechanisms, establish the importance of environmental exposures and determine disease severity, prognosis, and response to treatment.Supplementary Info


While remanent polarization, coercive field, and loop area of the same sample were 0.9 μC/cm2, 9.78 kV/cm, and 24.5 μC/cm2·V, respectively. Our results showed that a combination of graphene and ferroelectric ceramic additives are an excellent approach to significantly advance the performance of dielectric and ferroelectric properties of piezoelectric polymers for broad applications including energy storage.To address the limitations of piezoelectric polymers which have a low dielectric constant andto improve their dielectric and ferroelectric efficiency for energy storage applications, we designed and characterized a new hybrid composite that contains polyvinylidene fluoride as a dielectric polymer matrix combined with graphene platelets as a conductive and barium titanite as ceramic ferroelectric fillers. Different graphene/barium titanate/polyvinylidene fluoride nanocomposite films were synthesized by changing the concentration of graphene and barium titanate to explore the impact of each component and their potential synergetic effect on dielectric and ferroelectric properties of the composite. Results showed that with an increase in the barium titanate fraction, dielectric efficiency ofthe nanocomposite was improved. Among all synthesized nanocomposite films, graphene/barium titanate/polyvinylidene fluoride nanocomposite in the weight ratio of 0.15:0.5:1 exhibited thehighest dielectric constant of 199 at 40 Hz, i.e., 15 fold greater than that of neat polyvinylidene fluoride film at the same frequency, and possessed a low loss tangent of 0.6. However, AC conductivity and ferroelectric properties of graphene/barium titanate/polyvinylidene fluoride nanocomposite films were enhanced with an increase in the graphene weight fraction. Graphene/barium titanate/polyvinylidene fluoride nanocomposite films with a weight ratio of 0.2:0.1:1 possessed a high AC conductivity of 1.2 × 10 Dielectric constant of the resulting composite was 110 while its tanδ was 0.016 at 10 kHz [3/PVDF) composite possessing ε′ of 7 and tanδ as low as 0.03 [2 composites with polyvinyl alcohol (PVA) and poly(methyl methacrylate) (PMMA) with ε′ of 24.6 and 26.8 for both composites, respectively [Dielectric and piezoelectric polymer materials have attracted significant attention to replace piezoelectric ceramic materials used in various applications such as medical, automotive industry, and consumer electronics dueto their lightweight, flexibility, low-cost and low-acoustic impedance, and high piezoelectric constant ,2,3. Apaa (TiO2) ,11,12,13t 10 kHz . Ravindr as 0.03 . Sugumar3O4) [Another strategy to address the limitations of piezoelectric polymers is to add a small amount of conducting fillers into the polymer matrix to achieve high ɛ′. Some conducting fillers including multiwalled carbon nanotubes (MWCNT) , nano ir3O4) , silver 3O4) , and gra3O4)  etc. hav3O4) . The con3O4) ,23.3/PVDF composites by adding MWCNT filler. Synthesized three-phase composite showed enhanced dielectric efficiency with ε′ of 151 and tanδ of 0.08 at 100 Hz [3 reported by Zhang et al. possessed ε′ equal to 40.8 and tanδ of 0.055 at 100 Hz showing improvement in dielectric efficiency because it used Ag with a higher conductivity [3 and PVDF possessing ε′ and tanδ equal to 65 and 0.35, respectively at 1 MHz that demonstrated a promising potential of combined graphene/ceramic additives to advance performance of polymer dielectrics [To further advance the properties of dielectric polymer materials, the combination of both ceramic and conducting fillers has been explored to design ternary polymer composites. Yao et al. increased ε′ of BaTiOt 100 Hz . Anotheructivity . Wang etlectrics . AlthougIn this paper, we present the use of graphene as a conducting element to design three-phase graphene/barium titanate/polyvinylidene fluoride (G/BT/PVDF) nanocomposites with high ε′, low tanδ, and enhanced ferroelectric properties and explore performance for energy storage and capacitors applications. To demonstrate this concept, we selected graphene as the conducting filler because of its controllable conductive properties, size and 2D unique structure, high mechanical strength, and high electrical conductivity (σ) ,26. Amon4, Sigma-Aldrich, Gillman, Australia), hydrochloric acid , sulfuric acid , phosphoric acid , hydrogen peroxide , N,N–Dimethylforamide , barium titanate(IV)  and polyvinylidenefluroride  were of analytical grade and were used without further purification.Commercial natural graphite rocks  were purchased from an Australian mining site. Potassium permanganate (97% KMnOGraphene oxide (GO) was synthesized by improved method , and it Different G/BT/PVDF nanocomposite films of uniform thickness of 550 μmwere synthesized by the solution casting technique using different graphene content while keeping the concentration of BT (100 mg) and PVDF (1 g) constant. We explored several different G/BT ratios to analyzetheir influence on dielectric and ferroelectric properties and found an optimized composite formulation for future work. After characterization and calculating ε′ and tanδ of the above synthesized films, asuitable fraction of graphene with high ε′ and low tanδ (G:BT:PVDF = 0.15:0.1:1) was selected and further samples were synthesized with varying concentrations of BT while keeping the concentration ratios of graphene and PVDF (0.15:1) constant. The scheme of the designed composites with their key results is presented in −1 was used to identify the functional groups of synthesized nanocomposite films. Thermal stability was studied by using a thermal gravimetric analyzer  under air where the samples were heated from room temperature (RT) to 900 °C at a heating rate of 10 °C min−1. Dielectric characterization of the synthesized G/BT/PVDF nanocomposite films was carried out using precision impedance analyzer  at RT between 20 Hz to 1 MHz. Films were plated between copper electrodes and measurements were done at RT. Ferroelectric characterization of all samples was made by using Radiant Technologies Multiferroic testing system. Samples were placed between copper electrodes at RT.All samples including PVDF and ternary G/BT/PVDF nanocomposite films were analyzed to study their morphology by field emission scanning electron microscopy . Structural investigations were made by using X-ray diffraction  and Raman spectroscopy by using Raman microscope  equipped with LabSpec 6 software  A 532 nm laser line from He–Ne source was used for excitationand 600 grooves per mm grating was used. Acquisition time was 5 s and the accumulation time was 3 s. Fourier transform infrared (FTIR) spectroscopy  in transmittance mode and range 400–4000 cmMorphology of the synthesized G/BT/PVDF nanocomposite films was characterized by FESEM as shown in XRD analysis was carried out to investigate the crystal structure of the PVDF film and synthesized G/BT/PVDF nanocomposite films. −1 belong to the tetragonal structure of BT nanoparticles [−1 corresponds to beta (β) and gamma (γ) phases of PVDF. The GBP-III nanocomposite shows a band at 839 cm−1 confirming that PVDF is in β phase. The well-defined D and G bands of graphene appeared at 1333 cm−1 and 1557 cm−1 in the Raman spectra of GBP-III while these bands appear at 1333 cm−1 and 1546 cm−1, respectively in Raman spectra of GBP-IX. The intensity ratio of D and G bandsId/Ig was calculated to be 0.82 and 1.02 for GBP-III and GBP-IX, respectively. Id/Ig ratio shows that defects in graphene structure are more pronounced in GBP-III than in GBP-IX as the former has relatively higher graphene fraction than later [Raman spectra of neat PVDF film, GBP-III, and GBP-IX were recorded to confirm the presence of graphene, BT, and PVDF in synthesized G/BT/PVDF nanocomposite films. Results of Raman spectroscopy are in accordance with those of XRD except that it also shows graphene bands. Raman spectra are shown in articles . A very an later .−1 [−1 suggests the presence of β phase of PVDF [−1 is also indicating β phase PVDF. Two weak peaks at 2849 cm−1 and 2917 cm−1 correspond to C–H stretching of PVDF [−1 is present [−1 is indicative of entrapped remnants of DMF in nanocomposite films [FTIR spectra of all synthesized samples were recorded to further confirm the formation of G/BT/PVDF nanocomposites. FTIR spectra of G/BT/PVDF nanocomposites are shown in −1 . The pea of PVDF . The pea of PVDF . A chara present . But it te films .Thermal gravimetric analyses (TGA) of graphene, BT, neat PVDF film, and all synthesized G/BT/PVDF nanocomposite films were carried out to study their thermal stability. TG curves show that BT is stable over a high temperature range; even at 900 °C it is stable and does not decompose. Graphene decomposes with a rise in temperature and decomposes up to 95% around 600 °C. It was observed that incorporation of BT in the polymer improves thermal stability of the polymer from GBP-V to GBP-X. It is due to the high surface area contact of BT with the polymer matrix that results in the restriction of PVDF degradation . As BT fDielectric constant (ε′) of neat PVDF and all synthesized G/BT/PVDF nanocomposites was plotted against frequency as shown in At lower frequency, tanδ is low which may be due to the presence of ionizable hydroxyl group (OH) at the heterogeneous interface as well as the fact that an extendedtime is available for diploes to collide . Not onlac) of PVDF and all nanocomposite films is shown in ac of 1.2 × 10−4 (S/m) at 40 Hz. While a further increase in graphene might enhance the σac and ε′, a further rise in graphene content was not carried out due to the expected increase in tanδ. However, when BT content was further increased, it caused segregation of graphene sheets as shown in FESEM images in ac of GBP-IV. GBP-IX possesses the highest conductivity among nanocomposites with varying BT contents (GBP-V to GBP-X). It is due to the distance between graphene sheets reducing with increasing BT content to a certain extent. Here, tunneling conductance occurs through neighboring graphene sheets [AC conductivity  and loop area of PVDF film were 1.29 kV/cm and 0.00146 μC/cm2·V, respectively, as shown in The polarization electric field (P-E) hysteresis loop was studied to further analyze thegeneration of charge in the synthesized nanocomposite films. Analyses were carried out at RT. The thickness of each film was 550 μm, and the area of the electrode was 0.786 cm2, 9.78 kV/cm, and 24.5 μC/cm2·V, respectively. It is the highest among samples with different graphene content as shown in 2, 8.4 kV/cm, and 0.025 μC/cm2·V, respectively. Although these values are not much larger when compared to GBP-IV, they are still much better than that of neat PVDF. An increase in ferroelectric properties by increasing the BT content can be explained as follows:When BT content is low, there are fewer mobile charge carriers. Thus, energy dissipation is also low, and loop area is also low, but when BT fraction is increased, the number of charge-carrying particles is also increased. It results in increased energy dissipation and an enhanced loop area [It is evident from the ferroelectric analysis that by increasing graphene content while keeping BT fraction constant, ferroelectric properties are enhanced. Pr, Ec, and loop area of GBP-IV with maximum graphene fraction (200 mg) are 0.9 μC/cmoop area . A sligh2, 9.78 kV/cm, and 24.5 μC/cm2·V, respectively) among neat PVDF and all synthesized G/BT/PVDF nanocomposites. Our results demonstrate that the combination of graphene and ferroelectric ceramic additives is an excellent approach to enhance significantly the performance of dielectric and ferroelectric properties of piezoelectric polymers and can be used for broad applications, specifically, to be suitable for high performing energy storage and supercapacitors.In this paper, we designed and explored a concept to enhance dielectric and ferroelectric properties of piezoelectric polymers for energy storage applications by combining conductive graphene and ferroelectric ceramic (BT) additives. New hybrid composite films of G/BT/PVDF were synthesized with variations in dosage and ratio of graphene and BT to explore their influence on dielectric (ε′ and tanδ) and ferroelectric  values. In the first set of experiments, we kept the concentration of BT and PVDF constant and changed the concentration of graphene, until it reached a value with high ε′ and low tanδ. The optimized graphene fraction which showed good dielectric properties was selected for synthesis of another series of G/BT/PVDF nanocomposite films. In the second experiment, the concentration of BT was increased, andthe concentration of graphene and PVDF was fixed. GBP-VIII nanocomposite film with graphene, BT, and PVDF fraction (0.15:0.5:1) was found to have the highest ε′ values (199 at 40 Hz) and lowesttanδ (0.6) among all prepared samples, that is, it is highly suitable as a dielectric candidate for capacitors. Regarding the ferroelectric properties of prepared G/BT/PVDF nanocomposite films, results showed that GBP-IV (G:BT:PVDF = 0.2:0.1:1) has the best ferroelectric properties (Pr, Ec, and loop area of GBP-IV are 0.9 μC/cm


The large-scale production of high-quality and clean graphene devices, aiming at technological applications, has been a great challenge over the last decade. This is due to the high affinity of graphene with polymers that are usually applied in standard lithography processes and that, inevitably, modify the electrical proprieties of graphene. By Raman spectroscopy and electrical-transport investigations, we correlate the room-temperature carrier mobility of graphene devices with the size of well-ordered domains in graphene. In addition, we show that the size of these well-ordered domains is highly influenced by post-photolithography cleaning processes. Finally, we show that by using poly(dimethylglutarimide) (PMGI) as a protection layer, the production yield of CVD graphene devices is enhanced. Conversely, their electrical properties are deteriorated as compared with devices fabricated by conventional production methods. The unique properties of graphene, such as high conductivity, high carrier mobility at room temperature, high sensitivity of the electrical properties to surface phenomena and the existence of several routes for its surface functionalization, grant this 2D material plenty of application possibilities –8. Among2 layer, which was purchased from Graphene Platform. The graphene devices were produced in the field-effect transistor configuration (GFET) in two photolithography steps  . Then, t2 plasma . Finally2 plasma  using di2 plasma . After t2 plasma  was perfN-methyl-2-pyrrolidone (NMP), followed by rinsing in isopropanol (IPA) and deionized water , a solvent towards which LOR is inert ,e. Then,We performed Raman spectroscopy and electrical transport measurements, at room temperature, to correlate the size of well-ordered domains in graphene with its carrier mobility. The Raman spectroscopy was performed using an InVia Renishaw Raman spectrometer with a 514.5 nm laser and the electrical transport measurements were performed using a lock-in amplifier (SR-830 Stanford Research Systems).−1, shown in N,N-dimethylformamide (DMF) to clean the graphene devices. Finally, a third method (C3) consisted of graphene cleaning by H2/Ar (1:1) annealing at 300 °C for 2 h [2/Ar annealing, To remove residual PMGI from the graphene devices produced by procedure P2, we attempted three different cleaning methods. The first method (C1) consisted of cleaning the devices in a NMP bath. In the second cleaning method (C2), we used  for 2 h –18. NoneID/IG intensity ratio. For laser excitation with wavelength λL, the characteristic size of well-ordered domains in graphene can be estimated as:Structural disorder in graphene can be quantified through the La> 4 nm [which properly applies to a> 4 nm –21.La = 307 ± 50 nm. The size of well-ordered domains for graphene processed by both procedures P1 and P2 decreases to La ≈ 160 nm. From this, we infer that these procedures introduce approximately the same quantity of structural defects in graphene. Furthermore, the value of La showed no expressive decrease as the devices fabricated by procedure P2 are cleaned by method C1. However, when the cleaning is performed by methods C2 and C3, the size of well-ordered domains shows a further decrease, which suggests an increase of structural disorder in graphene [According to graphene ,22–23.Vg) for several devices produced by different lift-off procedures and cleaning methods. Since the neutrality point was beyond 100 V for several devices, we only consider here the transport by holes. Vg. This sublinear behavior is associated to a weak-point disorder in graphene, which emerges as a carrier density independent residual resistivity, ρs. The strong disorder and the charged-impurity disorder are responsible for the resistivity (μne)−1, in which μ is the mobility and n is the carrier density [Therefore, we have a situation in which the cleaning methods either do not clean the graphene surface or promote some degree of cleaning, but at the expense of introducing defects. In order to correlate the results obtained from Raman spectroscopy with the electrical transport properties of the graphene devices, we performed conductivity measurements as a function of gate voltage −1 as a function of Vg.where ρ = 1/σ is the measured resistivity of graphene . Then, t−1 and (ρ − ρs)−1 as a function of Vg for a graphene device produced by procedure P2. The mobility of the graphene devices produced by procedure P1, P2, C1, C2 and C3 follows a different trend than the size of the well-ordered domains in graphene. For example, according to 3 cm2/Vs, is considerably larger than the mobility of the graphene devices produced by procedure P2, which is μ = (1.5 ± 0.1) × 103 cm2/Vs. This result strongly suggests that the size of well-ordered domains in graphene is not the unique mechanism that limits its mobility in this case.d, related to crystal lattice defects, and in terms of the mobility μc, associated to charged impurities scattering centers, according to [Within the semiclassical Boltzmann transport formalism, the total mobility can be described in terms of the mobility μrding to –26:R, which gives rise to the mobility μd, as:The lattice defects can be modeled as a deep potential well of radius nd~ (2RLa)−1 is the defect density and kF corresponds to the Fermi wave vector [where e vector ,24. UsinG(2rs) is an analytical function that takes into account the interaction strength in graphene, rs is the interaction parameter and nc is the density of charged impurities [where purities –26.d, is the same for these devices. Thus, charged impurities must be the scattering source that distinguishes the mobility of the graphene devices produced by procedures P1 and P2. As the graphene devices produced by procedures P1 and P2 have approximately the same size of well-ordered domains , we assu2/Ar annealing (nd. Therefore, the considerable density of lattice defects, nd, and the density of charged impurities, nc, are responsible for the low mobility of C2 and C3 graphene devices.Additionally, nnealing  are not We performed electrical transport measurements and Raman spectroscopy investigations to compare the proprieties of CVD graphene-based devices processed using conventional photolithography with devices produced by a recently developed method using LOR as a sacrificial layer. We found that the PMGI molecules introduce disorder in graphene, which impairs the performance of the CVD-graphene based devices. We then applied the most common methods of post-photolithography cleaning in order to remove PMGI molecules. We were able to correlate the electrical mobility to the well-ordered domain size in devices that went through different cleaning procedures. We conclude that the use of LOR as sacrificial layer improves the CVD graphene device production yield, but impair the overall electronic performance of the devices.