Friction Layer Research Articles

Magnetic PDMS@SiO2/Fe3O4 Composite Friction Layer Material for Enhanced Friction Nanogenerator Output Performance

Triboelectric nanogenerators (TENG) have exhibited remarkable potential in harnessing stochastic low-frequency mechanical energy from oceanic surfaces, attributed to their versatile architectures and capability for extensive deployment. Nonetheless, the relatively modest power output per unit area remains a critical limitation impeding the advancement of TENG technology. Consequently, the innovation of novel material systems and devices to augment the output performance and efficiency of TENG is paramount in achieving effective ocean energy exploitation. In our study, a vertical contact PC-TENG was utilized as an energy harvester, with the incorporation of magnetic nano-oxide particles to bolster the output efficiency of TENG. This investigation represents the inaugural application of SiO2 and Fe3O4 nanoparticles within PDMS negative friction layers. This strategy augments the specific surface area, thereby improving the contact between the friction materials and enhancing charge transfer efficiency. Moreover, the magnetic properties of Fe3O4 facilitate charge separation on the material's surface, culminating in an elevated voltage output. Comprehensive characterizations were conducted using SEM, FTIR, electrometer, and contact angle meter, while simulations were corroborated with COMSOL Multiphysics field simulation software. The output performance witnessed optimization through the incorporation of Fe3O4, culminating in a peak open-circuit voltage (VOC) of 85.1212 V, a maximum short-circuits current (ISC) of 8.4037 μA, and a maximum transferred charge (QSC) of 0.5638 nC, reflecting enhancements of 28%, 32%, and 27%, respectively, compared to conventional PDMS materials. The peak output power, achieved with an impedance match of 55 MΩ, was recorded at 19.03 mW, marking a 70.8% improvement in output performance. The findings revealed that the contact angle of PDMS@SiO2/Fe3O4 composites reached 100.092°, enhancing hydrophobicity by 8% relative to traditional PDMS materials, thereby rendering it more suitable for humid environments. COMSOL Multiphysics field simulation results further substantiated the viability of the PDMS@SiO2/Fe3O4 composite friction layer material for applications in oceanic wave environments. Ultimately, a rectifier bridge was introduced to convert the alternating current generated by the PC-TENG into direct current. This research offers a novel paradigm for the utilization of TENG in the realm of marine energy.

Development of Turbocharging-Ability Hybrid Nanogenerators Comprising Bipolar PVDF-HFP/MXene Electrospun Composites.

Coupling piezo-active and triboelectric materials has recently emerged as an effective technique for developing high-performance hybrid nanogenerators (HNGs). This is the first paper to report the fabrication of piezo-active poly(vinylidene fluoride-hexafluoropropylene)(PVDF-HFP)/MXene-based hybrid composite fibers through conventional electrospinning. Here, the effect of MXene content (1-5%) on the surface potential and electrical performance of the as-synthesized composites is investigated and optimized. PVDF-HFP/3% MXene (PHM3)/Nylon 12+A-rGo (NY2)-HNG, which contains the best-performing composite (PMH3; containing 3% of MXene), exhibits turbocharging properties (charging a 10 µF capacitor with 16V within 100 s) and can continuously operate low-power electronics. Interestingly, PHM3 (with a negative surface potential) is transformed into PPHM3 (with a positive surface potential of +2190V) via corona poling. This study proposes a new class of HNGs containing frictional layers comprising bipolar PVDF-HFP/3% MXene composites (PHM3/PPHM3-HNG) with an excellent output performance of 297V and 5.1µA that exhibit broad application prospects in energy harvesting.

High-Performance Triboelectric Nanogenerator Based on Silk Fibroin-MXene Composite Film for Diagnosing Insomnia Symptoms.

In this study, we developed a flexible, biocompatible, and high-output electrical performance triboelectric nanogenerator (TENG) employing a silk fibroin (SF)-MXene composite film (SF-MXene-F) and a PDMS film as the friction layer. The inclusion of MXene in the SF film increased its surface charge density, presenting a practical approach to designing high-performance SF composite film-based TENGs. At a MXene content of 40%, our SF-MXene composite film-based TENG (SF-MXene-FTENG) achieved optimal output electrical performance, featuring a maximum open-circuit voltage (Voc) of 418 V, a maximum short-circuit current (Isc) of 11.6 μA, and a maximum output power density of 9.92 W/m2. The Voc and power densities of the SF-MXene-FTENG surpassed previously reported optimal values for SF-based TENGs by 1.6 and 3.8 times, respectively. Furthermore, leveraging the exceptional biocompatibility and light shading performance of TENGs, we designed a wearable smart TENG eye mask capable of diagnosing insomnia symptoms and monitoring sleep quality in real time. The SF-MXene-FTENG holds promising application potential as a wearable electronic device for diagnosing sleep-related diseases.

On Thermoelastic Impact Modelling of Frozen Composite Target During Pre – Heated Projectile Penetration Starts of Motion

This study investigates a composite double-layer structure for improved thermal shock resistance. A modified Hugoniot elastic limit model is presented for the composite, followed by a 2D thermo-elastic impact simulation using commercial software. The simulation focuses on a composite material under initial extreme low temperature conditions with alternating metallic (Steel, Aluminum) and non-metallic layers (Kevlar 49, Graphite). The frozen target is subjected to pre- heated projectile. The objective is to optimize the composite's durability by strategically placing reinforcement particles within specific layers. The analysis explores the effect of different particle types (oil, water, Aluminum, Steel) and sizes (0.3mm, 0.5mm, 1mm) on the composite's stress response. It was found that aluminum and steel particles significantly reduce stress compared to fluid/gas particles, confirmed qualitatively by literature. Kevlar particles within the SiCp layer enhance its resistance, while Aluminum particles within the Kevlar layer offer weight reduction benefits. Moreover, for Kevlar, larger particles improve resistance, and vice versa for the SiCp case. Considering weight, a particle size of 0.5mm is chosen for both layers. Moreover, a finite element analysis of the optimized composite model subjected to thermoelastic impact loading demonstrates its superior performance compared to the non-reinforced composite. Specific layer combinations (SiCp with Kevlar particles, Graphite or Kevlar with Aluminum particles) show the most significant stress reduction. Finally, separate 3D ballistic analysis was performed for Tungsten having 600m/sec projectile into 5 layered target with thickness of 2.8mm each layer and appropriate interaction friction (SiCp - Steel 304 - Al 7075-T651 - Kevlar 49 - Graphite Crystalline) during penetration time of 0.006sec at 300K. The dynamic explicit transient analysis was confirmed with the predecessors' analytic calculations.

Charge Capturing Effects of Boron Nitride Nanosheets on Enhanced Triboelectric Properties of Polyimide Nanocomposite Films in a Conductor-to-Dielectric Mode

Dielectric composite materials play a crucial role in the performance of triboelectric nanogenerators (TENGs) by influencing charge storage and transfer capabilities. In this study, we investigate the influence of boron nitride nanosheets (BNNS) on the triboelectric properties of polyimide (PI)-based dielectric nanocomposite films within a TENG setup employing a conductor-to-dielectric configuration and a contact-separation mode. To achieve this, we manufactured PI/BNNS nanocomposite films containing 1-10wt% BNNS with a thickness of ~14.67nm via a solution casting method, followed by thermal imidization. Thermogravimetric characterization revealed that the thermal stability of the nanocomposites improved with increasing BNNS content. Additionally, the triboelectric performance of the PI/BNNS films, used as the negative friction layer, was enhanced due to the electron-trapping capabilities at the BNNS-PI interface. Among the samples, the nanocomposite film containing 5wt% BNNS exhibited the most significant triboelectric output, generating a voltage of ~4.0V and a current of ~426.4nA. Moreover, the triboelectric AC output generated by the TENG using PI/BNNS nanocomposite films was successfully rectified into DC signals and subsequently stored in microcapacitors. This capability highlights the significant potential of PI/BNNS nanocomposite films for energy harvesting and storage applications, further supporting their suitability for integration into advanced flexible energy devices.

Fabrication of Self-powered Silicon Microneedles for Transdermal Drug Delivery

Abstract Transdermal drug delivery has been widely studied in recent years. Compared with other methods of drug delivery, this method has many advantages, such as convenient, improving patient compliance and avoiding first-pass effect. However, the low efficiency of this method needs to be overcome. In this paper, a micro-invasive transdermal drug delivery mechanism with synergic coupling of microneedle force field and triboelectric field is proposed, which can enhance the efficiency of transdermal drug delivery and is easy to operate and use. First, a silicon solid microneedle array was fabricated by micromachining technology, and its size parameters could be flexibly adjusted. Second, a metal layer with microstructure was fabricated on the back of the microneedle by sputtering technology as the positive friction layer of the triboelectric structure. Last, the microneedle and the triboelectric structure were combined into a single composite structure by using FPC wires. The experimental results showed that the transdermal amount increased with the increase of external excitation force, frequency and the number of microneedle arrays. Under the same conditions, the skin penetration of the two mechanisms combined was 3-8 times higher than that of the single use.

High-Performance Rotating Structure Triboelectric-Electromagnetic Hybrid Nanogenerator for Environmental Wind Energy Harvesting.

As environmental energy harvesting gains increasing importance in self-powered systems and large-scale energy demands, wind energy, as a clean, pollution-free, and renewable source, has garnered widespread attention. However, achieving efficient wind energy collection remains challenging. This study proposes a high-performance rotating structure triboelectric-electromagnetic hybrid nanogenerator designed for environmental wind energy harvesting. By optimizing the magnetic circuit design of the electromagnetic generator, the dispersed radial magnetic field is converted into a unified axial magnetic field, enabling efficient power generation with only a single annular coil, thereby simplifying the generator design and reducing manufacturing and maintenance costs. Additionally, a triboelectric nanogenerator design with soft contact friction between polycarbonate (PC) fur and fluorinated ethylene propylene (FEP) film was implemented, optimizing the spacing between the electrode and friction layers, thus enhancing output performance and device durability. Furthermore, we simulated and experimentally tested the output waveform of the designed hybrid generator structure, with the results showing a high degree of similarity, further validating the rationality of the device design and providing guidance for structural optimization. Subsequently, we achieved efficient energy storage using an energy management circuit (EMC). With the integration of the EMC, the generator successfully powered a Bluetooth temperature and humidity sensor at a wind speed of 10 m/s, achieving wireless transmission, and demonstrating its potential application in traffic signal systems and other natural environmental systems. This research provides an important reference for further exploration of novel wind energy harvesting technologies.

Micro water energy harvesting system based on tubular triboelectric nanogenerator

Abstract Constructing a micro-water energy-harvesting system for the power supply of micro-nano sensors in pipeline liquid transmission networks is of great significance. In this study, a micro water energy harvesting system based on a tubular triboelectric nanogenerator was designed, which achieves efficient energy harvesting and conversion by directly collecting the charge of the friction layer without the electrostatic induction effect. First, the working principle of the liquid-solid triboelectric nanogenerator is analyzed based on multi-physic coupling, and the potential distribution in the charge transfer process is analyzed. Second, the effects of liquid flow, pipe length, inner diameter, and material on the output characteristics of the triboelectric nanogenerator were investigated. Finally, the load power supply characteristics of the triboelectric nanogenerator were presented. The output characteristics of the liquid-solid triboelectric nanogenerator were proportional to the flow rate and inversely proportional to the inner diameter of the pipe. The output power of the liquid-solid triboelectric nanogenerator can be charged and stored by the capacitor through the rectifier bridge, and at least 30 LED lamp beads can be driven at a flow rate of 650 ml·min-1. This research has the potential to be applied to the construction of self-powered liquid-state monitoring intelligent sensors in pipeline networks.

High-Performance Triboelectric Nanogenerator with Double-Side Patterned Surfaces Prepared by CO2 Laser for Human Motion Energy Harvesting

The triboelectric nanogenerator (TENG) has demonstrated exceptional efficiency in harvesting diverse forms of mechanical energy and converting it into electrical energy. This technology is particularly valuable for powering low-energy electronic devices and self-powered sensors. Most traditional TENGs use single-sided patterned friction pairs, which restrict their effective contact area and overall performance. Here, we propose a novel TENG that incorporates microwave patterned aluminum (MC-Al) foil and microcone structured polydimethylsiloxane (MC-PDMS). This innovative design utilizes two PMMA molds featuring identical micro-hole arrays ablated by a CO2 laser, making it both cost-effective and easy to fabricate. A novel room imprinting technique has been employed to create the micromorphology of aluminum (Al) foil using the PMMA mold with shallower micro-hole arrays. Compared to TENGs with flat friction layers and single-side-patterned friction layers, the double-side-patterned MW-MC-TENG demonstrates superior output performance due to increased cone deformation and contact area. The open-circuit voltage of the MW-MC-TENG can reach 141 V, while the short-circuit current can attain 71.5 μA, corresponding to a current density of 2.86 µA/cm2. The power density reaches 1.4 mW/cm2 when the resistance is 15 MΩ, and it can charge a 0.1 μF capacitor to 2.01 V in 2.28 s. In addition, the MW-MC-TENG can function as an insole device to harvest walking energy, power 11 LED bulbs, monitor step speed, and power a timer device. Therefore, the MW-MC-TENG has significant application potential in micro-wearable devices.

Self-Powered, Flexible, Wireless and Intelligent Human Health Management System Based on Natural Recyclable Materials.

Combining wearable sensors with modern technologies such as internet of things and big data to monitor or intervene in obesity-induced chronic diseases, such as obstructive sleep apnea, type II diabetes, cardiovascular diseases, and Alzheimer's disease, is of great significance to the self-health management of human beings. This study designed a loofah-conducting graphite four friction layer enhanced triboelectric nanogenerator (LG-TENG) and developed a health management system for human motion recognition and early warning of sleep breathing abnormalities. By uniformly spraying and depositing conductive graphite on the surface of the loofah and the elastic film cross-interlocking bending structure design, the signal strength of the LG-TENG has been improved by 390%. The stable output signal is still maintained after 1500 s of continuous operation at a frequency of 2 Hz. LG-TENG can realize accurate motion analysis by muscle contraction state. Combining different deep learning models resulted in 98.1% accuracy in recognizing seven categories of displacement speeds for an individual and 96.46% accuracy in recognizing seven categories of displacement speeds for three individuals. In addition, the sleep breathing monitoring early warning system was developed by integrating Bluetooth wireless transmission and upper computer analysis technology. This system aims to analyze and provide real-time warnings for sleep-breathing abnormalities. This research promotes an innovation of TENG technology based on the advantages of natural materials, recyclability and low cost. It offers new ideas for self-health management and scientific exercise for obese people, showing a broad application prospect.

Effect of friction layer thickness on energy conversion efficiency of traveling wave rotary ultrasonic motor

Abstract Due to its compact size and resistance to electromagnetic interference. Applications for traveling wave rotary ultrasonic motors (TRUM) include robotic joint drives and aerospace.The motor’s energy conversion efficiency is impacted by the characteristics of the friction layer, yet the underlying mechanism influencing the efficiency remains unreported. Using the previously created finite element model, the mechanism via which the amount of thickness within the friction layer influences the motor output characteristics is examined.Analysis is done on the variations in motor loss, energy conversion efficiency, and input-output characteristics. The computation results show that when the friction layer is less than 0.4 mm, the machine’s output speed increases as the friction layer’s thickness decreases.The results of the calculation indicate that when the friction layer thickness is between 0.05 and 0.4 mm, the motor’s output torque and speed would drop. The findings indicate that the output torque and motor torque decrease as the friction layer thickness increases when it is between 0.05 and 0.4 mm. Both the viscoelastic losses and the motor’s energy conversion efficiency rise.Research shows that the friction layer thickness has a huge impact on the motor and cannot be ignored, providing a reference for the application of motors in industries such as robot joints.

Mechanical and tribological properties of high entropy carbide-based micro-nano ceramic composites

(NbTaTiWZr)C-based micro-nano composites were fabricated by spark plasma sintering employing multi-layer graphene (MLG), Ni, and Al2O3 as reinforcements. It is demonstrated that excellent mechanical properties were achieved for MLG, Ni, and Al2O3 hybrid addition with a hardness of 21.73 GPa, a flexural strength of 572.4 MPa, and a fracture toughness of 7.65 MPa m1/2. Enhanced densification together with inhibited grain growth contributed to the simultaneously improved hardness and flexural strength. The major toughening mechanisms were determined as microcracks, crack deflection, crack bridging, crack stopping, MLG wall, MLG pull-out, MLG bending, and MLG wrapping grains. Furthermore, outstanding tribological performance occurred to the (High entropy ceramic) HEC-Ni-Al2O3-MLG with a friction coefficient of 0.23 and wear rate of 4.32 × 10−7mm3N−1m−1, as a function of graphene acting as a lubricating friction layer and the enhanced mechanical responses.

CFD investigation of supersonic two parallel expansions nozzles

This paper aims to validate the design contours and result parameters of the newly developed Dual Expansion Nozzle (DEN) using the Fastran software when it enters the non-adaptation regime with the increase in altitude and variation of the Nozzle Pressure Ratio (NPR). DEN design and Computational Fluid Dynamic (CFD) application utilize the High Temperature (HT) model defined by a calorically imperfect and thermally perfect gas, providing good accuracy compared to PG model. The computational domain is decomposed into subdivisions of structured grids using the algebraic grid generator software CFD-GEOM. The mesh convergence was analyzed using three mesh resolutions: coarse, medium, and fine. A comparison was made between the two conventional nozzles, MLN and the newly developed BPN, as both are currently used in aerospace propulsion to enhance aerodynamic performance. If a rocket engine operates under strongly over-expanded conditions with ambient pressure considerably higher than the nozzle exit pressure, and by increasing NPR value, the flow separates from the wall and can lead to high side loads. These loads are reduced in DEN. The flow separation point is observed close to the exit section for the DEN in comparison with Minimum Length Nozzle (MLN) and Best Performance Nozzle (BPN) for the same NPR, resulting in low flow separation and low side load effects for DEN. This result demonstrates a small loss in the exit Mach number, leading to less loss in the thrust coefficient and a small effect of boundary layer friction for DEN. Enhanced over-expanded aerodynamics is observed in DEN compared to MLN and BPN. The application is made for air with an exit Mach number equal to 3.00.

Flexible Fiber Shaped Self-Powered System Based on Conductive PANI for Signal Sensing and Energy Harvesting.

As science and technology advance, people are increasingly inclined to use sustainable and portable wearable electronic devices. The traditional supporting power source, batteries, suffers from issues of flexibility and lifespan, severely constraining the development of wearable devices. Alternatively, the self-powered system, serving as a power source, can effectively collect energy from the surrounding environment, achieving maintenance-free operation and high adaptability, which has attracted widespread research. The coaxial fiber-structured self-powering system proposed in this study is based on a supercapacitor (SC) and a triboelectric nanogenerator (TENG). The carbon fiber (CF) has polyaniline (PANI) and rGO connected to it, and a friction layer of silicone rubber is wrapped around the outside. The conductivity of the fiber was increased by multiple PANI graftings, and a coaxial fiber-type TENG with a 2 mm diameter was created. Following weaving, the TENG displays a high power density of 576 mW m-2 and an open-circuit voltage of 160 V and a short-circuit current of 9 μA. In addition, the flexible fiber-shaped supercapacitor uses NiAl-LDHs@CF as the negative electrode and AC@CF as the positive electrode, showing a specific capacitance of up to 281.4 mF cm-2. Furthermore, the SC and TENG are assembled into a coaxial self-power supply system, which has excellent performance and shows extensive potential applications in the field of wearable device power supply.

Computational influences of convection micropolar fluid influx and permeability on characteristics of heating rate and skin friction over vertical plate

This manuscript merits at examining of an embedded orthogonal plate inside porous domain exposed to uniform heat influx to elaborate on how micro polar fluid factors and permeability characteristic affect the local skin friction, heating rate, and angular velocity inside boundary layer. The plate is subjected to forced convective micro polar fluid influx under steady, incompressible, and viscous circumstances. To facilitate dependable numerical solution, similarity approach is implemented to mutate set of coupled governing equations relevant to the adopted study into a constrained dimensionless differential equations. Computational analysis has been executed hiring Runge-Kutta scheme by Matlab function bvp4c to settle the governing equations. Study's results are highlighted graphically the impact of micro polar fluid factors on the local skin friction, heating rate, and angular velocity curves. High degree of acceptability of present findings compare with prior research results. It is found that the rising of Darcy parameter drives to decrease linearly both heating rate and local skin friction. Among the examined factors, the benchmark parameter of decreasing skin friction is the porosity. Additionally, it is found that an increasing of Prandtl number and micro rotation element lead to enhance Nusselt number. Once curves of micro rotation are interfered at certain distance from the plate due to increase in porosity, Darcy, Forchheimer's, and microelement rotation, the micro rotation curves are inverted.

Self-powered wearable remote control system based on self-adhesive, self-healing, and tough hydrogels

The advent of the fifth-generation mobile communication network era induces a great potential for the design and development of self-powered wearable electronic devices. Hydrogels, as a typical material for flexible electrodes, have been widely employed in self-powered wearable electronic devices. However, the hydrogel-based triboelectric nanogenerator (H-TENG) is usually compromised by the challenges in data collection, operational stability, and manufacturability due to the unstable combination between the friction layer and the electrode layer, the occurrence of hydrogel damage during prolonged operation, and also the difficulty of machining sticky hydrogel electrodes. In the present study, a composite hydrogel composed of acrylamide, crotonyl alcohol, and 4-carboxyphenylboronic acid was synthesized via ultraviolet crosslinking, which was specially developed for H-TENG and wearable wireless remote control interface, featuring with excellent stretchability and mechanical strength as well as self-healing and self-adhesive properties. The open-circuit voltage of the H-TENG prepared with the hydrogel reached up to 165 V, and the output voltage remained almost unchanged following 10,000 cycles of compression test. Additionally, a wearable wireless remote control system was designed that could accurately control the multiple appliances and adjust different working modes using the H-TENG. Consequently, the development of the H-TENG and wearable wireless remote control system has the potential to provide a new methodology for the application of next-generation wearable devices in various areas, such as smart homes, as a representative example.

Структурные особенности и трибологические свойства многослойных высокотемпературных плазменных покрытий

Introduction. Multilayer high-temperature coatings obtained using plasma spraying, are studied. The combination of layers of different chemical and phase compositions made it possible to increase wear resistance by 1.5–2.0 times. The purpose of this work is to study the influence of the chemical composition of sprayed coatings on the phase composition, structure, micromechanical and tribological characteristics under conditions of dry sliding friction of surface layers. Materials and methods of research. Coatings A and B consist of sequentially sprayed layers. The first and second layers were sprayed in a reducing atmosphere: the first layer was a heat-resistant self-fluxing powder of two systems: 1 – Fe-Cr-Si-Mn-B-C for coating A and 2 – Fe-Ni-Si-Mn-B-C for coating B; the second layer was a mixture of self-fluxing powder with iron powder in a 1:1 ratio. The third layer was obtained by spraying iron powder in an oxidizing atmosphere to form a metal oxide coating. To create a layer of scale on the surface, coated specimens were subjected to high-temperature annealing at a temperature of 1,000 ℃. The chemical composition and nature of the distribution of elements over the thickness of the coatings were determined by micro-X-ray spectral analysis using a TWSCAN scanning electron microscope with an Oxford energy-dispersive attachment. Microhardness and micromechanical properties were studied using an instrumental microhardness tester of the Fischerscope HM2000 XYm system at a load of 0.980 N. Determination of tribological properties was carried out on a laboratory installation using the “finger-disc” scheme at loads of 30, 75, 100 and 130 N. To measure roughness parameters and obtain 3-D profilometry of surfaces after testing, a non-contact profilometer-profiler Optical profiling system Veeco WYKO NT 1100 was used. Results and discussion. Metallographic studies have shown that the formed multilayer coatings consist of an internal metal layer and an external oxide layer with a total thickness of the entire coating up to 800–850 μm. It is established that the first sprayed layer has the highest level of microhardness, which is due to the high-volume fraction of the strengthening phases contained in it (~ 95 %). It is shown that the coating A has increased wear resistance, which is expressed by minimal weight loss (~ 1.5 times less than that of the coating of the coatimg B), the friction coefficient was f = 0.3 for coating A and f = 0.4 for coating B. The study of wear surfaces has shown that for all selected test loads under sliding friction conditions, the coating of both compositions was preserved, even at a maximum load of 130 N.

Surface mechanical rolling treatment-introduced gradient nanostructured Inconel 625 alloy with enhanced high-temperature wear resistance

Heterogeneous gradient nanostructures induced through surface treatment of nickel-based superalloys hold significant promise for enhancing wear resistance. In this study, a 700 µm ultra-thick gradient nanostructured (GNS) strengthening layer was fabricated on the surface of an Inconel 625 alloy plate via surface mechanical rolling treatment (SMRT). Subsequently, the tribological behaviors and wear resistance mechanisms of coarse-grained (CG) and GNS samples at temperatures ranging from 25 ℃ to 800 ℃ were comparatively investigated. The results indicated that the gradient nanostructures significantly enhanced the high-temperature wear resistance of the samples, which wear characterized by low coefficient of friction (COF), wear rate and thin friction layer. This enhancement was attributable to the stability and excellent hot hardness of the gradient nanostructures during friction.

Thermal-driven self-healing and recyclable thermosetting polyurethane resins for energy harvesting

Improving the mechanical properties, self-healing capabilities, and recyclability of friction layer materials is crucial for the advancement of high-performance triboelectric nanogenerators (TENG). In this study, self-healing cross-linked polyurethanes were synthesized through the prepolymer technique, employing the Diels-Alder (D-A) reaction between the furan ring and Bismaleimide (BMI). The tensile strength of PU film with 10 wt% MBI is 54 MPa, and the shape recovery rate is 96.99 %. Moreover, it exhibits excellent self-healing and recyclable characteristics. Surface cracks can be healing within 10 min under heat, reshaped through hot pressing, while retaining 93.3 % of its mechanical properties. Additionally, the 2 cm × 2 cm area PU-based TENG can generate a short-circuit current, open-circuit voltage, transferred charge, and power density of 3.6 μA, 89 V, 29 nC, and 2.5 W/m2, respectively, at a frequency of 1 Hz. Futhermore, the self-healing efficiency of mechanical properties and the triboelectric output performances were found to reach 93.3 % and 98 %, respectively, after reprocessing. This study introduces a promising method for enhancing self-healing, shape memory characteristics, and the design of wearable TENG devices.

Highly Porous, Ultralight, Biocompatible Silk Fibroin Aerogel-Based Triboelectric Nanogenerator.

This study presents the fabrication of an ultralight, porous, and high-performance triboelectric nanogenerator (TENG) utilizing silk fibroin (SF) aerogels and PDMS sponges as the friction layer. The transition from two-dimensional film friction layers to three-dimensional porous aerogels significantly increased the specific surface area, offering an effective strategy for designing high-performance SF aerogel-based TENGs. The TENG incorporating the porous SF aerogel exhibited optimal output performance at a 3% SF concentration, achieving a maximum open circuit voltage of 365 V, a maximum short-circuit current of 11.8 μA, and a maximum power density of 7.52 W/m2. In comparison to SF-film-based TENGs, the SF-aerogel based TENG demonstrated a remarkable 6.5-fold increase in voltage and a 4.5-fold increase in current. Furthermore, the power density of our SF-based TENG surpassed the previously reported optimal values for SF-based TENGs by 2.4 times. Leveraging the excellent mechanical stability and biocompatibility of TENGs, we developed an SF-based TENG self-powered sensor for the real-time monitoring of subtle biological movements. The SF-based TENG exhibits promising potential as a wearable bioelectronic device for health monitoring.