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A woven carbon fiber (WCF)-based triboelectric nanogenerator (TENG)-cum-structural supercapacitor is an excellent multifunctional device for clean energy harvesting and storage. This type of device has high load-bearing capacity and functions smoothly under severe outdoor conditions. Herein, WCF-based multifunctional TENG is reported that generated 8.9 W m−2 power with 84% energy conversion efficiency. The energy generated by the TENG was simultaneously stored in a connected supercapacitor that provide 1.93 Wh kg−1 of energy density and delivers 39.23 W kg−1 of power density. The specific surface area of the WCF was enhanced several hundred-fold by coating with an N-doped Zn–Cu selenide nanoporous material, thereby enabling higher energy generation and elevated storage capacity of the device. The TENG use a polyester-based solid polymer electrolyte as the negative electrode and polydimethylsiloxane-coated WCF as the positive electrode. The device has a very high coulombic efficiency with high mechanical strength and ability to resist massive impact. An application of the multifunctional device was demonstrated. These types of multifunctional devices have great potential in the self-charging automobile, aerospace, sensor, and electronics sectors.

In this study, melamine–naphthalene covalent polyamic acid and its metal carboxylate salts were synthesized as building blocks of nanofillers (Nt–Mn–PA–COOM, M = H, Li, Na, and K). The Nt–Mn–PA–COOM nanofillers were added as a dopant to vinyl ester resin at 1–5 wt% and their flame retardancy and thermal properties were evaluated. The flame retardancies of 5 wt% of Nt–Mn–PA–COOK–VE and Nt–Mn–PA–COONa–VE were found to improve the heat release rate by up to 95% and 90%, respectively, in comparison with the pristine vinyl ester (VE) composite. These results demonstrated significant progress in the fireproofing performance of VE composites. The burning times of Nt–Mn–PA–COONa–VE and Nt–Mn–PA–COOK–VE composites were shown to be higher 10.6 min, and 12.1 min, respectively, when compared with the pure VE composite (6.28 min). Also, the burning rates of Nt–Mn–PA–COONa–VE and Nt–Mn–PA–COOK–VE concerning flame retardancies were decreased from 11.92 min to 7.07 and 6.19 min, respectively. The delay in burning time, and the reduction of burning rate clearly refer to the enhancement of flame retardancy behavior of the Nt–Mn–PA–COOM–VE composites. It was found that 5 wt% of nanofiller dopants Nt–Mn–PA–COOM–VE (M = Na, and K) in VE was the ideal loading for considering the integrated perspective for flame retardancy applications. The excellent flame retardancy and thermal performance of the Nt–Mn–PA–COOM–VE (M = Na, and K) composites made them promising candidates for developing novel flame retardancy nanofiller dopants.

The lymphatic system is critical for maintaining the homeostasis of lipids and interstitial fluid and regulating the immune cell development and functions. Developmental anomaly-induced lymphatic dysfunction is associated with various pathological conditions, including lymphedema, inflammation, and cancer. Most lymphatic endothelial cells (LECs) are derived from a subset of endothelial cells in the cardinal vein. However, recent studies have reported that the developmental origin of LECs is heterogeneous. Multiple regulatory mechanisms, including those mediated by signaling pathways, transcription factors, and epigenetic pathways, are involved in lymphatic development and functions. Recent studies have demonstrated that the epigenetic regulation of transcription is critical for embryonic LEC development and functions. In addition to the chromatin structures, epigenetic modifications may modulate transcriptional signatures during the development or differentiation of LECs. Therefore, the understanding of the epigenetic mechanisms involved in the development and function of the lymphatic system can aid in the management of various congenital or acquired lymphatic disorders. Future studies must determine the role of other epigenetic factors and changes in mammalian lymphatic development and function. Here, the recent findings on key factors involved in the development of the lymphatic system and their epigenetic regulation, LEC origins from different organs, and lymphatic diseases are reviewed.

Polypropylene (PP) nanocomposite films reinforced with surface-modified nanoclay, maleic anhydride-grafted PP (PP-g-MA), and surfactants, such as cetyl-trimethyl-ammonium bromide (CTAB) and octadecyl-trimethyl-ammonium bromide (ODAB), were fabricated by extrusion, and the effect of surfactant type used for the nanoclay and the take-up speed of extrusion on the mechanical properties and crystallinity of the nanocomposite films were investigated. Multi-scale hybrid composites (MHCs) consisting of plasma-treated plain woven carbon fiber (WCF) and nanocomposite films were manufactured by hot pressing. Flexural and impact tests were performed to measure the mechanical properties at various plasma treatment times. Scanning electron microscopy and X-ray photoelectron spectroscopy (XPS) were used to observe the surface morphology and detect polar functional groups, respectively. Results of XPS analysis showed a considerable increase in the oxygen atomic percentage after plasma treatment. The mechanical properties of the MHCs were greatly affected by the presence of nanoclay in the composite and the plasma treatment. The flexural modulus and strength, impact force, and absorbed impact energy of the MHC specimens treated with plasma (15 s) and reinforced with nanoclay/ODAB(5:1, 1.5 wt%) and PP-g-MA(3 wt%), increased by 69, 87, 49 and 54%, respectively, compared to the neat non-plasma-treated WCF/PP composites.

The development of a flexible electronic skin (e-skin) highly sensitive to multimodal vibrations and a specialized sensing ability is of great interest for a plethora of applications, such as tactile sensors for robots, seismology, healthcare, and wearable electronics. Here, we present an e-skin design characterized by a bioinspired, microhexagonal structure coated with single-walled carbon nanotubes (SWCNTs) using an ultrasonic spray method. We have demonstrated the outstanding performances of the device in terms of the capability to detect both static and dynamic mechanical stimuli including pressure, shear displacement, and bending using the principles of piezoresistivity. Because of the hexagonal microcolumnar array, whose contact area changes according to the mechanical stimuli applied, the interlock-optimized geometry shows an enhanced sensitivity. This produces an improved ability to discriminate the different mechanical stimuli that might be applied. Moreover, we show that our e-skins can detect, discriminate, and monitor various intensities of different external and internal vibrations, which is a useful asset for various applications, such as seismology, smart phones, wearable human skins (voice monitoring), etc.

In this study, we investigated the gauge factor and compressive modulus of hybrid nanocomposites of exfoliated graphite nanoplatelets (xGnP) and multiwalled carbon nanotubes (MWCNTs) in a polydimethylsiloxane matrix under compressive strain. Mechanical and electrical tests were conducted to investigate the effects of nanofiller wt %, the xGnP size, and xGnP:MWCNT ratio on the compressive modulus and sensitivity of the sensors. It was found that nanofiller wt %, the xGnP size, and xGnP:MWCNT ratio significantly affect the electromechanical properties of the sensor. The compressive modulus increased with an increase in the nanofiller wt % and a decrease in the xGnP size and xGnP:MWCNT ratio. However, the gauge factor decreases with a decrease in the nanofiller wt % and xGnP size and an increase in the xGnP:MWCNT ratio. Therefore, by investigating the piezoresistive effects of various factors for sensing performance, such as wt %, xGnP size, and xGnP:MWCNT ratio, the concept of one- and two-dimensional hybrid fillers provides an effective way to tune both mechanical properties and sensitivity of nanocomposites by tailoring the network structure of fillers.

Numerous techniques have been developed for the non-destructive evaluation (NDE) of impact damage in fiber reinforced plastics (FRPs), following the increasing demands for their safety and maintenance. Considering the large-scale detection and the vast amount of data involved, machine learning (ML) can be utilized in NDE for damage type analysis and impact damage localization. Furthermore, self-sensing using carbon fiber in FRPs is an emerging technique for NDE that can be combined with ML. In this study, ML was used to design smart FRPs by selecting the fiber type and electrode distance considering the cost and electromechanical sensitivity. Furthermore, a novel algorithm for structural health self-sensing was suggested using an artificial neural network. The developed ML algorithms are advantageous since they do not require a theoretical model when all the factors and the variables of FRPs, such as the maximum absorbed impact energy, maximum impact force, initial electrical resistance, number of electrodes, fiber types, and electrode distance, are to be considered. The algorithm was trained using given input data and the target, and the output could be successfully obtained when new input data were provided. Therefore, the proposed ML algorithms hold great potential and applicability to FRP design and for NDE methods.

Highly sensitive and flexible composite sensors with pressure and temperature sensing abilities are of great importance in human motion monitoring, robotic skins, and automobile seats when checking the boarding status. Several studies have been conducted to improve the temperature-pressure sensitivity; however, they require a complex fabrication process for micro-nanostructures, which are material-dependent. Therefore, there is a need to develop the structural designs to improve the sensing abilities. Herein, we demonstrate a flexible composite with an enhanced pressure and temperature sensing performance. Its structural design consists of a multilayered composite construction with an elastic modulus gradient. Controlled stress concentration and distribution induced by a micropatterned structure between the layers improves its pressure and temperature sensing performance. The proposed composite sensor can monitor a wide range of pressure and temperature stimuli and also has potential applications as an automotive seat sensor for simultaneous human temperature detection and occupant weight sensing.

The laser-induced synthesis of nanostructures provides an innovative and unique way to shorten the overall processing time in comparison to traditional methods, while allowing precise control of the growth. This is the novel research to report continuous laser beam-assisted uniform growth of aligned nanowires, nanorods and nanotubes on woven carbon fibers (WCF) within a short period of time. The morphologies of the nanostructures were finely controlled by tuning the laser power, beam speed and exposure time. We compared the nanowire/nanorod growth patterns to those obtained with pulsed laser processed growth. The nanostructured-WCF was then used as an electrode and a woven Kevlar fiber (WKF) sheet as a separator for the fabrication of supercapacitor-type sensors. The supercapacitor displays excellent electrochemical and mechanical performance with outstanding multifunctionality. The self-energized supercapacitor exhibits high sensitivity with good cyclic stability. The device functions very well, with few errors, under various environmental conditions. We believe that our supercapacitor-type sensor will be extremely beneficial for the detection of structural problems in bridges, buildings, aerospace vehicles and automobiles, and facilitate the precise motion control of different types of instruments.

Progresses in sensor and energy technologies have been an important driving force for the rapid development of these industries and have drawn the attention of researchers on environmental concerns. In particular, carbon nanomaterial (carbon nanotubes, graphene, graphite, etc.)-based composites are widely used for sensor and energy harvesting applications owing to their excellent electrical, thermal, and mechanical properties. In this review, we have discussed various aspects of the use of carbon nanocomposites for the development of sensor and energy harvesting devices. These devices have shown outstanding sensing and energy harvesting performances. Various carbon nanomaterial-based composites with sophisticated structural and material designs have been developed to improve their sensing performance for various applications. We have also reviewed recent technological developments in carbon nanocomposite-based energy generators that adopt thermoelectric and triboelectric working mechanisms. Further research on the development of carbon nanocomposites with enhanced sensing and energy harvesting properties will expand the range of their applications to automotive, aerospace, artificial skin, healthcare, and environmental/infrastructure industries.

In this study, we propose analytical and experimental methods to predict and detect deformation and interlaminar crack propagation in carbon fiber-reinforced plastics (CFRPs) based on electrical resistance measurement. The electromechanical behavior of CFRP was investigated from the elastic region to crack propagation. The CFRPs were subjected to tensile, three-point bending, and Mode I dual cantilever beam loads, and the signature electromechanical response was correlated to subsequent deformations and crack propagation. The self-sensing investigation was extended to different fiber combinations and electrode placement schemes to obtain customized sensitivity. The experimental results were verified through finite element analysis . In parallel, equivalent electrical circuit modelling was conducted to obtain the “resistor components” that exist in a CFRP and predict the electromechanical behavior under various mechanical loads.

Fiber laser cutting of CFRP sheets was investigated using a 2 kW multi-mode fiber laser, focusing on how the cut quality factors, such as kerf width, kerf depth, matrix evaporation width, matrix recession width, kerf taper angle, matrix damage zone, and cut surface morphology, change as laser power, laser scanning speed, and the number of laser passes are varied. By designing a systematic experiment on a large process window, several important parameters for kerf width, kerf depth, matrix evaporation width, and matrix recession width were identified, and using them, it was verified that the beam scanning speed is a dominant factor for minimizing thermal damages. Also, circular rings were observed in each carbon fiber at the cut surfaces, and it looked as if they were generated when each fiber was thermally fused in the radial direction. A larger number of laser passes was found to contribute to a smooth surface morphology, because of the formation of highly-fused surfaces, which prevents fiber delamination and pull-outs. Optimum process conditions were also identified by comparing various cut quality factors.

Structural supercapacitors provide a variety of opportunities for woven carbon fibers in portable electronics, hybrid automobiles and aerospace applications. We describe herein the synthesis of bimetallic Cu-Co selenide nanowires based on woven carbon fibers, and their use as electrodes in supercapacitors. Woven Kevlar fiber is used as separator for the electrodes and a polyester resin with an ionic liquid and lithium salt is used as solid polymer electrolyte. The supercapacitors exhibit efficient energy storage and significant enhancements in mechanical strength (89.38%) and modulus (70.41%) over those of bare woven carbon fiber base supercapacitors. The specific capacitance of these supercapacitors increases from 0.197 F g−1 to 28.63 F g−1 after the growth of nanowires, with accordingly high energy density (191.64 mW h kg−1) and power density (36.65 W kg−1). In situ mechano-electrochemical tests of these supercapacitors yield excellent capacitance retention (77.3%) at the mechanical failure point (481.29 MPa).

Zinc oxide nanorod (ZnO NR)-grown woven carbon fiber/polyamide 6 composites were fabricated using hydrothermal synthesis and thermoplastic resin transfer molding. The in-situ polymerization of e-caprolactam, which exhibits extremely low viscosity and high reaction speed, enabled excellent penetration of the resin into the densely grown ZnO forest on the carbon fibers. This further increased the mechanical interlocking and chemical interaction between the fiber and resin, leading to enhanced interfacial bonding. By increasing the number of oxygen functional groups and the surface roughness of the fiber surfaces through an atmospheric plasma treatment, the ZnO NRs were observed to grow even with very low growth-solution concentrations (20 mM), fewer seed cycles (4), and a short hydrothermal treatment time (4 h). By using the plasma-treated carbon fibers for ZnO NR growth, the impact resistance and in-plane shear strength were enhanced by up to 72 and 50%, respectively, as compared to carbon fiber composites without ZnO NRs, while the use of ZnO precursors and growth time was minimized.

Nylon 6,6 nanocomposites containing well-dispersed graphene oxide (GO) and carbon nanotubes (CNTs) were successfully fabricated via in situ interfacial polymerization between two immiscible phases: organic phase assisted by poly(vinylpyrrolidone, PVP) surfactant containing adipoyl chloride with dispersion of GO and CNTs; aqueous phase containing hexamethylenediamine. Prior to polymerization, GO was functionalized with thionyl chloride, resulting in acyl-chloride-functionalized GO (AGO). The effect of incorporation of AGO and PVP on the state of dispersion was investigated. It was observed that the addition of AGO and PVP reduced particle flocculation, leading to a well-dispersed suspension as verified using dispersion stability measurement and UV–Vis spectroscopy. The interfacial interaction between the carbon nano-fillers and nylon 6,6 chain can be induced via hydrogen and covalent bonding between them. Thermal analyses revealed nuclei crystallization in nylon 6,6 nanocomposites was promoted by the strong nucleating behavior of AGO, and the thermal stability was improved. Tensile tests of the composite films (nylon 6,6/AGO, CNT) showed increases of 122 and 152%, respectively, in the tensile strength and modulus as compared to the neat polymer. This suggests that the interfacial interaction between nylon 6,6 and AGO/CNT contributes to enhanced load transfer in nanocomposites, thus enhancing the mechanical properties of the nanocomposites.

Carbon fiber (CF) holds structural self-sensing capability using its electrical resistance so that electromechanical behavior of carbon fiber reinforced plastic (CFRP) was investigated for using CF and carbon-glass hybrid fiber (CGHF). CGHF contains CF in either warp or weft, whereas glass fiber is perpendicularly woven in the other. Electrical resistance of CF monofilament whose diameter is 8 μm was increased when tensile strain was applied in fiber direction, which is called piezoresistive effect. When CF is gathered into a bundle, similar piezoresistive effect was observed. Moreover, distance change between the adjacent CF also led to the resistance change, because the number of electrical contacts can be differed with respect to the tow gap. We call this phenomenon “inter-tow interaction.” Another discriminative electromechanical contact is “inter-ply interaction” which has electromechanical contact between adjacent plies. Likewise, several electromechanical factors hold structural self-sensing capability. Therefore, real-time non-destructive evaluation (NDE) and structural health monitoring (SHM) can be realized with carbon fiber. The CF for the self-sensing can be constituted in various forms in a polymer matrix such as a plain-woven fabric, a uni-directional fabric and a grid. The self-sensing CF grid can be a compromised arrangement between the sensing performance and the material cost. In addition, the self-sensing algorithms of CFs can be comprehended by electrically equivalent circuit models. Reversely, the sensor design can be aided by the equivalent model which contains the aforementioned interactions.

Health state monitoring and prognostics and management of composite were investigated with piezoresistivity data based on the electromechanical behavior of carbon fibers during dual cantilvever bending testing. Crack length in real-time and remaining crack length were calculated with measured electrical resistance. Prediction of crack length was estimated based on prediction result of electromechanical behavior. This research indicated optimized in situ diagnosis and prognosis of carbon fiber reinforced composites with self-sensing data. Self-sensing capability of self-sensing data using electrical resistance was investigated which is applicable to both SHM and PHM.

Functionalized graphene–polymer nanocomposites have gained significant attention for their enhanced mechanical, thermal, and antibacterial properties, but the requirement of multi-step processes or hazardous reducing agents to functionalize graphene limits their current applications. Here, we present a single-step synthesis of thermally reduced graphene oxide (TrGO) based on shellac, which is a low-cost biopolymer that can be employed to produce poly(vinyl alcohol) (PVA)/TrGO nanocomposites (PVA–TrGO). The concentration of TrGO varied from 0.1 to 2.0 wt.%, and the critical concentration of homogeneous TrGO dispersion was observed to be 1.5 wt.%, below which strong interfacial molecular interactions between the TrGO and the PVA matrix resulted in improved thermal and mechanical properties. At 1.5 wt.% filler loading, the tensile strength and modulus of the PVA–TrGO nanocomposite were increased by 98.7% and 97.4%, respectively, while the storage modulus was increased by 69%. Furthermore, the nanocomposite was 96% more effective in preventing bacterial colonization relative to the neat PVA matrix. The present findings indicate that TrGO can be considered a promising material for potential applications in biomedical devices.