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Triboelectric separation has recently been investigated as a novel process for dry enrichment and separation of protein of various crops like wheat flour. The triboelectric effect allows for the separation of starch and protein particles in an electric field based on their different charging behavior despite having a similar density and size distribution. Particles are triboelectrically charged in a charging section before being separated in an electric field based on their polarity. While the charging section is crucial, the influence of process parameters remains largely unexplored. Thus, the influence of the charging sections' dimensions and the particle concentration as process key parameters was investigated experimentally. Varying the length (0, 105, and 210 mm) showed that the protein shift increases with the length (max. 0.53%) during separation. Varying the diameter (6, 8, and 10 mm) influenced the charging behavior, resulting in an increase in protein accumulation on the negative electrode as the diameter decreased. Varying the mass flow of flour (40, 80, 160, and 320 g·h−1) also affected the separability, leading to a maximum protein shift of 0.61%. Based on the observed results, it is hypothesized that the electrostatic agglomeration behavior of oppositely charged particles is directly affected by alterations in machine parameters. These agglomerates have a charge-to-mass ratio that is too low for separation in the electric field. [ABSTRACT FROM AUTHOR]

Materials that can emit light under optical/mechanical stimulation are usually called photoluminescent/mechanoluminescent (PL/ML) materials. PL materials are used in diverse fields for half a century. While, ML materials have burst out in the last two decades, and now are showing great application potential in the fields of anti‐counterfeiting, information storage, and stress imaging. It is of great significance to explore new luminescent materials with PL and ML dual response. In this study, Tb3+‐doped Ca3Ga4O9 phosphors with color‐tunable PL and non‐pre‐irradiation ML properties are reported. Ca3Ga4O9 exhibits a broadband blue emission centering at 425 nm, which originates from the 4T2‐4A2 transition of electrons in d orbits of Ga3+. Due to the energy transfer from host to Tb3+, color‐tunable emission from blue to cyan, and ultimately to green can be realized by increasing the concentration of Tb3+. Particularly, ML is seen from Ca3Ga4O9:Tb3+ under grinding and from the Ca3Ga4O9:Tb3+/PDMS film under bending or stretching originated from the triboelectric mechanism. The non‐pre‐irradiation ML behavior is evidenced by the contrast thermoluminescence (TL) experiments. This study not only provides a new candidate toward multi‐purpose luminescent applications, but also demonstrates a good case in which the triboelectric effect can efficiently trigger the non‐pre‐irradiation ML behavior. [ABSTRACT FROM AUTHOR]

Nanogenerators have garnered significant interest as environmentally friendly and potential energy-harvesting systems. Nanogenerators can be broadly classified into piezo-, tribo-, and hybrid nanogenerators. The hybrid nanogenerator used in this experiment is a nanogenerator that uses both piezo and tribo effects. These hybrid nanogenerators have the potential to be used in wearable electronics, health monitoring, IoT devices, and more. In addition, the versatility of the material application in electrospinning makes it an ideal complement to hybrid nanogenerators. However, despite their potential, several experimental variables, biocompatibility, and harvesting efficiency require improvement in the research field. In particular, maximizing the output voltage of the fibers is a significant challenge. Based on this premise, this study aims to characterize hybrid nanogenerators (HNGs) with varied structures and material combinations, with a focus on identifying HNGs that exhibit superior piezoelectric- and triboelectric-induced voltage. In this study, several HNGs based on coaxial structures were fabricated via electrospinning. PVDF-HFP and PAN, known for their remarkable electrospinning properties, were used as the primary materials. Six combinations of these two materials were fabricated and categorized into homo and hetero groups based on their composition. The output voltage of the hetero group surpassed that of the homo group, primarily because of the triboelectric-induced voltage. Specifically, the overall output voltage of the hetero group was higher. In addition, the combination group with the most favorable voltage characteristics combined PVDF-HFP@PAN(BTO) and PAN hollow, boasting an output voltage of approximately 3.5 V. [ABSTRACT FROM AUTHOR]

The application study of triboelectric and electrostatic effects, with roots tracing back hundreds of years, has continued to evolve and develop in industrial production, science, technology, and other fields. Numerous methods have been proposed for the preparation and processing of triboelectric materials, resulting in significant advancements in their charge density and application range. This paper aims to provide a comprehensive understanding of the application progress of the triboelectric effect. It begins by summarizing the fundamental theoretical mechanism of triboelectrification. Subsequently, a detailed review of various applications related to triboelectric effect and electrostatic induction is conducted, encompassing electrostatic adsorption, electret formation, electrostatic self-assembly, triboelectric generator, self-powered sensor, and mechanical force catalysis. Furthermore, different triboelectric materials and their preparation and modification methods are also explored in accordance with different application scenarios. Finally, this paper discusses the future development prospects and challenges associated with the triboelectric effect. It also emphasizes the necessity for further research and development in specific fields, offering valuable insights for future scientific research and practical implementation.

Artificial biomaterials with dynamic mechano-responsive behaviors similar to those of biological tissues have been drawing great attention. In this study, we report a TiO2-based nanowire (TiO2NWs) scaffolds, which exhibit dynamic mechano-responsive behaviors varying with the number and amplitude of nano-deformation cycles. It is found that the elastic and adhesive forces in the TiO2NWs scaffolds can increase significantly after multiple cycles of nano-deformation. Further nanofriction experiments show the triboelectric effect of increasing elastic and adhesive forces during the nano-deformation cycles of TiO2NWs scaffolds. These properties allow the TiO2NW scaffolds to be designed and applied as intelligent artificial biomaterials to simulate biological tissues in the future. [ABSTRACT FROM AUTHOR]

Flexible and wearable devices are attracting more and more attention. Herein, we propose a self-powered triboelectric nanogenerator based on the triboelectric effect of fish scales. As the pressure on the nanogenerator increases, the output voltage of the triboelectric nanogenerator increases. The nanogenerator can output a voltage of 7.4 V and a short-circuit current of 0.18 μA under a pressure of 50 N. The triboelectric effect of fish scales was argued to be related to the lamellar structure composed of collagen fiber bundles. The nanogenerator prepared by fish scales can sensitively perceive human activities such as walking, finger tapping, and elbow bending. Moreover, fish scales are a biomass material with good biocompatibility with the body. The fish-scale nanogenerator is a kind of flexible, wearable, and self-powered triboelectric nanogenerator showing great prospects in healthcare and body information monitoring. [ABSTRACT FROM AUTHOR]

Abstract Artificial biomaterials with dynamic mechano-responsive behaviors similar to those of biological tissues have been drawing great attention. In this study, we report a TiO2-based nanowire (TiO2NWs) scaffolds, which exhibit dynamic mechano-responsive behaviors varying with the number and amplitude of nano-deformation cycles. It is found that the elastic and adhesive forces in the TiO2NWs scaffolds can increase significantly after multiple cycles of nano-deformation. Further nanofriction experiments show the triboelectric effect of increasing elastic and adhesive forces during the nano-deformation cycles of TiO2NWs scaffolds. These properties allow the TiO2NW scaffolds to be designed and applied as intelligent artificial biomaterials to simulate biological tissues in the future.

Nanogenerators have garnered significant interest as environmentally friendly and potential energy-harvesting systems. Nanogenerators can be broadly classified into piezo-, tribo-, and hybrid nanogenerators. The hybrid nanogenerator used in this experiment is a nanogenerator that uses both piezo and tribo effects. These hybrid nanogenerators have the potential to be used in wearable electronics, health monitoring, IoT devices, and more. In addition, the versatility of the material application in electrospinning makes it an ideal complement to hybrid nanogenerators. However, despite their potential, several experimental variables, biocompatibility, and harvesting efficiency require improvement in the research field. In particular, maximizing the output voltage of the fibers is a significant challenge. Based on this premise, this study aims to characterize hybrid nanogenerators (HNGs) with varied structures and material combinations, with a focus on identifying HNGs that exhibit superior piezoelectric- and triboelectric-induced voltage. In this study, several HNGs based on coaxial structures were fabricated via electrospinning. PVDF-HFP and PAN, known for their remarkable electrospinning properties, were used as the primary materials. Six combinations of these two materials were fabricated and categorized into homo and hetero groups based on their composition. The output voltage of the hetero group surpassed that of the homo group, primarily because of the triboelectric-induced voltage. Specifically, the overall output voltage of the hetero group was higher. In addition, the combination group with the most favorable voltage characteristics combined PVDF-HFP@PAN(BTO) and PAN hollow, boasting an output voltage of approximately 3.5 V.

The detection and feedback of displacement and velocity significantly impact the control accuracy of the linear feed system. In this study, we propose a flexible and self-powered displacement sensor based on the triboelectric effect, designed for seamless integration into linear feed systems. The displacement sensor comprises two parts, the mover and stator, operating in a sliding mode. This sensor can precisely detect the displacement of the linear feed system with a large detection range. Additionally, the sensor is capable of real-time velocity detection of linear feed systems, with an error rate below 0.5%. It also offers advantages, such as excellent flexibility, compact size, stability, easy fabrication, and seamless integration, with linear feed systems. These results highlight the potential of the self-powered displacement sensor for various applications in linear feed systems. [ABSTRACT FROM AUTHOR]

Haptic feedback, also known as tactile sensing, plays a vital role in human interactions with the external environment. The artificial replication of tactile sensations using triboelectric sensors has sparked the attention of the scientific community by developing advanced electronic skins with haptic perception. In this work, we design and fabricate different flexible tactile sensors based on the triboelectric effect. The triboelectric sensors were evaluated in respect of their ability to identify different materials that were in contact with the sensor. Our results show that the triboelectric signal depends on the nature of the substrate, and a clear distinction among different substrates could be obtained. [ABSTRACT FROM AUTHOR]

Triboelectric energy harvester may be used to power small electronic devices for many applications such as temperature and humidity sensors, accelerometers, and GPS tracking devices. This paper has developed the theoretical model of sliding mode triboelectric energy harvester to predict the harvested energy due to mechanical vibration/motion. The model has been solved using the 4th order Runge–Kutta Method. An experimental setup has been fabricated to validate the numerical results. Numerical results reveal that harvested energy depends upon various input factors like the type of motion, external resistance, contact area, width, and dielectric thickness. A parametric study has been presented to maximize the harvested energy with an average acceleration of 35 m/s2 between the triboelectric films (PTFE and Nylon with contact area 10 cm × 10 cm), maximum current, and a voltage obtained is 0.6 µA & 3 V, respectively, and 10 LEDs are lightened. Further, a comparison study has been carried out between contact mode TEH and sliding mode TEH to predict the better mode of energy harvesting. [ABSTRACT FROM AUTHOR]

In this paper we report the study of mechanical energy harvesting of ambient energy based on triboelectric effect. We choose the bulk form of poly-tetrafluoroethylene (PTFE) as electronegative (E-) material and human hand and plywood as the electropositive (E+) materials, respectively making a single electrode based triboelectric generator (TEG). The E+ and E-material were rubbed together to produce a voltage output, which was measured by using a sensitive electrometer. This investigation was carried out for different surface morphology, surface areas of contact, thickness and types of electrode contacts and rubbing frequency. It was observed that sufficient voltage and charge generation was achieved to power low energy devices like LED bulbs, with the highest voltage generation of ~6.2 V for rectangular PTFE sheet, having one surface coated with a thin film of copper for making electrode and other one is made rough using sandpaper, as the E-material and plywood as the E+ material. We observed that the voltage output is influenced by the surface morphology, type of E+ material for the same E-material, frequency of rubbing strokes and frictional area of contact. [ABSTRACT FROM AUTHOR]

The complex process of wound healing depends on the coordinated interaction between various immunological and biological systems, which can be aided by technology. This present review provides a broad overview of the medical applications of piezoelectric and triboelectric nanogenerators, focusing on their role in the development of wound healing technology. Based on the finding that the damaged epithelial layer of the wound generates an endogenous bioelectric field to regulate the wound healing process, development of technological device for providing an exogenous electric field has therefore been paid attention. Authors of this review focus on the design and application of piezoelectric and triboelectric materials to manufacture self-powered nanogenerators, and conclude with an outlook on the current challenges and future potential in meeting medical needs and commercialization.

Abstract Charge transfer mechanisms of contact electrification (CE) are essential for widening applications of the triboelectric nanogenerator, and thus are widely studied by scientists around the world. However, the quantitative modeling of CE, especially that between polymers, is still lacking. Herein, a model was proposed to describe the contributions from different mechanisms, including electron transfer and mass transfer in polymer/polymer CE through the field‐assisted thermionic emission, where three groups of charge transfer mechanisms were distinguished by the polarity of the charge transfer and the corresponding electric field. The results indicated that the total generated charge in CE is actually much larger than the measured net surface charge, confirming the bidirectional material‐dependent charge transfer mechanisms between two surfaces, which is meaningful for understanding the millennium puzzle in triboelectrification and provides a new perspective for promoting the applications to tailor surface charge generation.

In this study, a concept and design of a self-powered sensor that utilizes a triboelectric effect to evaluate the condition of tensile bolted joints was proposed. Based on the fact that the triboelectric charge yields electrostatic voltage induced by the separation of the contacting rough surfaces, the proposed sensor is a film-shaped triboelectric sensor made of inexpensive materials being installed between the objects to be fastened. The principle of the sensor is that it detects microscale relative motions between the contacting surfaces against an external vibratory load when the integrity of the fastened joint is compromised due to a decrease in the bolt's fastening force. In this study, we designed and fabricated triboelectric sensor and tested it on a tensile bolted joint specimen subjected to inertial vibratory loading, and it was experimentally shown that the output voltage amplitude of the sensor increased as the bolt's fastening force decreased. In addition, a modeling study was performed to explain the unexpected decrease in voltage amplitude observed at medium preloads, by combining the triboelectric and mechanical models with the experimental results of two different external circuit configurations. Estimation of the triboelectric charge density at the contacting surfaces was performed, which was found to be consistent with the contact mechanics model assumed. Finally, the calculation of the sensor output voltage based on the presented mechanical/triboelectric model was provided, confirming the validity of the modeling study. [ABSTRACT FROM AUTHOR]

A simple and affordable triboelectric device is fabricated to harvest mechanical energy and convert it to electrical energy. Based on a double‐dielectric‐layered (Nylon and PTFE) structure, a lateral sliding mode triboelectric energy harvester (SM‐TEH) has been fabricated. The fabricated SM‐TEH device is linked to the slider‐crank mechanism for smooth operation. The dimension of the fabricated device has been used as 10.1 cm × 10.1 cm. An experimental study has been conducted for various rotational speeds at different external resistance. Additionally, an electrical model has been developed to validate the experimental results. After that, it has been carefully examined to see how the material, structure, and experimental parameters may affect the output performance of the SM‐TEH. Later, a thorough investigation of the effects of the dual factors, including the effective triboelectric layer thickness, contact area, external resistance, and rotational speed (in rpm), was conducted. The relationship between conversion efficiency and external resistance is investigated to obtain the maximum efficiency at optimum external resistance. Further, the cost analysis of the SM‐TEH device is presented to study the commercialization of the device for practical application. The feasibility of the designed SM‐TEH is demonstrated by lighting on 40 red light‐emitting diodes (LEDs). The AC signals generated are then converted into DC signals using a bridge rectifier. Capacitors of various sizes (1, 2.2, 3.3, 10, 47 μF) store the output voltage without external load resistance. [ABSTRACT FROM AUTHOR]

Triboelectric nanogenerators (TENGs) is a term used to describe harvested electricity made by the use of electrostatic charge between two triboelectric materials. It works in 4 different methods; vertical contact-separation mode, linear sliding mode, single-electrode mode, and free-standing mode. This project focuses on vertical contact-separation mode whereby two materials of different electron affinities are vertically placed in contact with each other, and as they are separated from each other, an electric potential is induced in the interfacial region and the electrodes, causing a flow of electrons within the circuit to maintain equilibrium in the electrostatic field. The two materials are then brought in contact again, and the triboelectric charges disappear, causing the induced electrons to return. The project examines the triboelectric effect of the vertical contact-separation mode as it is tested against four different combinations of different materials: Aluminum and Copper as fixed electrodes, and Polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), Kapton, and skin as the triboelectric layers. The results of this experiment showed that PTFE as a triboelectric layer generated the highest peak voltage of 0.888 V among the 4 different materials, with an estimated surface charge density of 8.58525 x 10-12 C.m-2. This shows that the developed DC-TENG can generate satisfactory results and can be further improved to be used in various applications.

Optical emission from gas molecules is considered an excellent solution to gas detection because of its fairly high sensitivity and selectivity. However, its further development is constrained by its large size, high energy consumption, and security risks. Herein, a self‐powered gas sensing solution is proposed by taking advantage of the optical emission of triboelectric discharge (TD). Based on the triboelectric effect, the high output voltage of ≈kV can lead to producing optical emissions through gas discharges, including emission spectra and discharge images, which are affected by gas species and pressure. By means of machine learning, the optical emission signals process the ability to recognize 60 gas atmospheres simultaneously, with an accuracy of 97.67%. With the assistance of the mobile phone or closed‐circuit television, a self‐powered gas sensing system based on TD may serve as a portable detecting device and a vital component of the Internet of Things system. [ABSTRACT FROM AUTHOR]

The triboelectric energy harvester (TEH) could power small electronic devices, including temperature sensors, GPS trackers, accelerometers, and humidity sensors. An experimental and simulation investigation on the harvesting of sinusoidal mechanical vibration utilizing a triboelectric mechanism is presented in this article. According to numerical results, the amount of energy harvested depends on many input elements such as movement of the upper electrode, external resistance, phase angle, contact area, and thickness of the dielectric layer. The influences of the dual parameters, including the dielectric thickness, contact area, external resistance, phase angle, and vibration frequency on electrical output, were investigated systematically. The stability and durability test are performed for fabricated TEH. Simultaneously, a bridge rectifier has been used to convert produced A.C. signals into D.C. signals. The output voltage is stored in capacitors of various sizes (0.47, 3.3, 10, 22, 47 µF) with no load resistances. The feasibility of the developed TEH is proved by lighting up 35 red Light-Emitting Diodes (LEDs). [ABSTRACT FROM AUTHOR]

Triboelectric nanogenerators (TENGs) is a term used to describe harvested electricity made by the use of electrostatic charge between two triboelectric materials. It works in 4 different methods; vertical contact-separation mode, linear sliding mode, singleelectrode mode, and free-standing mode. This project focuses on vertical contactseparation mode whereby two materials of different electron affinities are vertically placed in contact with each other, and as they are separated from each other, an electric potential is induced in the interfacial region and the electrodes, causing a flow of electrons within the circuit to maintain equilibrium in the electrostatic field. The two materials are then brought in contact again, and the triboelectric charges disappear, causing the induced electrons to return. The project examines the triboelectric effect of the vertical contact-separation mode as it is tested against four different combinations of different materials: Aluminum and Copper as fixed electrodes, and Polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), Kapton, and skin as the triboelectric layers. The results of this experiment showed that PTFE as a triboelectric layer generated the highest peak voltage of 0.888 V among the 4 different materials, with an estimated surface charge density of 8.58525 x 10- 12 C.m-2. This shows that the developed DC-TENG can generate satisfactory results and can be further improved to be used in various applications. [ABSTRACT FROM AUTHOR]

Charge transfer mechanisms of contact electrification (CE) are essential for widening applications of the triboelectric nanogenerator, and thus are widely studied by scientists around the world. However, the quantitative modeling of CE, especially that between polymers, is still lacking. Herein, a model was proposed to describe the contributions from different mechanisms, including electron transfer and mass transfer in polymer/polymer CE through the field‐assisted thermionic emission, where three groups of charge transfer mechanisms were distinguished by the polarity of the charge transfer and the corresponding electric field. The results indicated that the total generated charge in CE is actually much larger than the measured net surface charge, confirming the bidirectional material‐dependent charge transfer mechanisms between two surfaces, which is meaningful for understanding the millennium puzzle in triboelectrification and provides a new perspective for promoting the applications to tailor surface charge generation. [ABSTRACT FROM AUTHOR]

The present study is aimed at the revelation of subtle effects of steam flow through a conical coil heat exchanger on an enzyme, incubated near the heat exchanger, at the nanoscale. For this purpose, atomic force microscopy (AFM) has been employed. In our experiments, horseradish peroxidase (HRP) was used as a model enzyme. HRP is extensively employed as a model in food science in order to determine the influence of electromagnetic fields on enzymes. Adsorption properties of HRP on mica have been studied by AFM at the level of individual enzyme macromolecules, while the enzymatic activity of HRP has been studied by spectrophotometry. The solution of HRP was incubated either near the top or at the side of the conically wound aluminium pipe, through which steam flow passed. Our AFM data indicated an increase in the enzyme aggregation on mica after its incubation at either of the two points near the heat exchanger. At the same time, in the spectrophotometry experiments, a slight change in the shape of the curves, reflecting the HRP-catalyzed kinetics of ABTS oxidation by hydrogen peroxide, has also been observed after the incubation of the enzyme solution near the heat exchanger. These effects on the enzyme adsorption and kinetics can be explained by alterations in the enzyme hydration caused by the influence of the electromagnetic field, induced triboelectrically by the flow of steam through the heat exchanger. Our findings should thus be considered in the development of equipment involving conical heat exchangers, intended for either research or industrial use (including miniaturized bioreactors and biosensors). The increased aggregation of the HRP enzyme, observed after its incubation near the heat exchanger, should also be taken into account in analysis of possible adverse effects from steam-heated industrial equipment on the human body. [ABSTRACT FROM AUTHOR]

Summary: The new field of applications for triboelectric materials is based on the combination of high physical durability and charge properties of ZnO semi‐conductor thin films, which have been explored in this work. ZnO films are successfully deposited by the RF magnetron sputtering method in the wurtzite phase. A post‐heat‐treatment process of the as‐deposited films is carried out in an oxygen atmosphere at 973 K. According to the X‐ray diffraction patterns, scanning electron microscope (SEM), and atomic force microscopy (AFM) images, the average particle size of the ZnO films increases gradually with the heat‐treatment process. The semilogarithmic current‐voltage and frequency‐dependent capacitance measurements of thin films under various bias voltages are done to understand the charge transfer resistance, conductivity and capacitance properties which directly affect the figure of merit (FOMm) of the triboelectric layer material performance. The charge density and triboelectric charge density values in present study for heat‐treated thin films are 11 and 121 mC/m2, respectively. These findings might be used as a good candidate for further triboelectric device energy research areas in the near future. [ABSTRACT FROM AUTHOR]

Multifunctional motion sensors have broad applications in the field of the internet of things (IoT). An octopus-shaped self-powered motion sensor is proposed to monitor the acceleration, motion direction, rotation speed and angle of objects. The charge transfer analysis of the sensor is carried out based on the positive piezoelectric effect, contact electrification effect and electrostatic induction. The influence of the surface microstructure and doping ZnO on the sensor sensitivity is investigated, and the improved film increases the sensor sensitivity by 13.58%. It is found that the output voltage decreases as the frequency increases. At the same frequency, the sensor output voltage amplitude is proportional to the acceleration amplitude. The test results show that the sensor can identify the motor rotation speed and angle, and the linear running direction and the motion state of the sweeping robot. Furthermore, the proposed sensor is cheap and beneficial for large-scale use. [ABSTRACT FROM AUTHOR]

As a state of matter, liquids exist in an extremely wide range, including water such as that in oceans and rivers, as well as various solutions, oils, liquid metals, etc. Due to the fluidity of liquids, the triboelectric effect based on them often shows unexpected results and can be used in complex environments. Herein, the latest research on working principles of the triboelectric effect at liquid–solid, liquid–liquid, and liquid–gas interfaces are reviewed. The factors affecting triboelectric charge generation and the output performance of liquid‐interfaces‐based TENGs (LI‐TENG) in terms of material, environment, and structure are systematically discussed. Besides, to harvest the ubiquitously existing energy in various forms, studies about the hybridization of LI‐TENG with other energy harvesters for syngeneic single‐source and multisource energy harvesting are also reviewed. Moreover, the performances of LI‐TENGs as energy harvesters and as novel sensors with various applications are reviewed. Finally, opportunities and challenges in the future development of LI‐TENG are discussed.

In this study, a concept and design of a self-powered sensor that utilizes a triboelectric effect to evaluate the condition of tensile bolted joints was proposed. Based on the fact that the triboelectric charge yields electrostatic voltage induced by the separation of the contacting rough surfaces, the proposed sensor is a film-shaped triboelectric sensor made of inexpensive materials being installed between the objects to be fastened. The principle of the sensor is that it detects microscale relative motions between the contacting surfaces against an external vibratory load when the integrity of the fastened joint is compromised due to a decrease in the bolt’s fastening force. In this study, we designed and fabricated triboelectric sensor and tested it on a tensile bolted joint specimen subjected to inertial vibratory loading, and it was experimentally shown that the output voltage amplitude of the sensor increased as the bolt’s fastening force decreased. In addition, a modeling study was performed to explain the unexpected decrease in voltage amplitude observed at medium preloads, by combining the triboelectric and mechanical models with the experimental results of two different external circuit configurations. Estimation of the triboelectric charge density at the contacting surfaces was performed, which was found to be consistent with the contact mechanics model assumed. Finally, the calculation of the sensor output voltage based on the presented mechanical/triboelectric model was provided, confirming the validity of the modeling study.

Among various energy harvesting technologies, triboelectricity is an epoch-making discovery that can convert energy loss caused by the mechanical vibration or friction of parts into energy gain. As human convenience has emerged as an important future value, wireless devices have attracted widespread attention; thus, it is essential to extend the duration and lifespan of batteries through energy harvesting or the application of self-powered equipment. Here, we report a transistor, in which the gate rotates and rubs against the dielectric and utilizes the triboelectricity generated rather than the switching voltage of the transistor. The device is a triboelectric transistor with a simple structure and is manufactured using a simple process. Compared to that at the stationary state, the output current of the triboelectric transistor increased by 207.66 times at the maximum rotation velocity. The approach reported in this paper could be an innovative method to enable a transistor to harness its own power while converting energy loss in any rotating object into harvested energy. [ABSTRACT FROM AUTHOR]

This paper reports a substantiated method and a designed device for controlling the concentrations of air ions in premises in accordance with the European standards SBM 2015. The use of an ultrasonic humidifier with a capacity of 25 W for two hours increases the concentration of negative ions around the device from 240 to 560 cm-3, positive ones ‒ from 260 to 410 cm-3. The intensity of the electrostatic field of a polymeric coating decreases from 5.1 to 0.2 kV/m. The disadvantage of the humidifier is a small radius of influence (1.0–1.5 m) and the inability to control the polarity of ions. It has been experimentally established that air cooling systems (split systems) deionize the air of the premises. Degrees of deionization and dominating polarity are unpredictable and different for devices of different manufacturers and brands. To control the ion composition of the air simultaneously with the maintenance of normative relative humidity and stresses of static fields, the structure was proposed and the effectiveness of a bipolar ultrasonic air ionizer with adjusted performance and dominating polarity has been tested. The maximum productivity of the ionizer is 4,000–5,000 cm-3. The radius of exposure is 5 m (reducing the concentration of ions with a distance to 500 cm-3). To pass the ionized air through an air capacitor, the number and predominant polarity of air ions are regulated by the polarity and voltage on the covers of the capacitor. It was established that in order to service a room with an area of 50 m2, an ultrasonic emitter with a capacity of 25 W would suffice. The adjustability of the device performance makes it possible to reduce or increase the service area. The ability to purify air from suspended particles is shown. During the two hours of operation of the ionizer, the dust content decreased from 4.3–4.4 mg/m3 to 1.4–1.6 mg/m3 [ABSTRACT FROM AUTHOR]

Vibration energy is abundant in the atmosphere and has the potential to be harvested by various mechanisms. A triboelectric energy harvester (TEH), based on the triboelectric mechanism, has substantial potential to harvest vibration energy due to its high performance, extensive availability, and low-cost electrical energy production. This article examines the mechanical and electrical behaviors of vertical contact mode TEHs. TEHs have been designed and built to harvest low-frequency mechanical vibration produced by human footsteps on floor tiles and vehicle movement. Here, an experimental study is presented using various mechanical vibration modes including sinusoidal, square, triangular, and ramp modes. Experimental results showed that the device produced a power output between 17.91 μW and 25.83 μW at a root mean square (RMS) voltage level between 33.49 V and 129 V under loading resistance of 5 MΩ at 10 Hz resonant frequency and 1 g acceleration. The energy density of the TEH (243.7 µJ/cm3) was higher for ramp vibration. In addition, the stability and the durability of the fabricated TEH are analyzed. The developed TEH can convert mechanical energy into electric energy and light 65 red light-emitting diodes (LEDs). The device can extract energy from a broad range of low-frequency (<10 Hz) vibrations and has vast application potential in self-powered electronic devices and systems. [ABSTRACT FROM AUTHOR]

Haptic feedback plays a crucial role, continuously offering individuals vital information about their external surroundings through physical contact. Therefore, rapid advances in human-friendly biomimetic electronics and flexible devices, have allowed the development of advance electronic skins for artificial haptic sensation. In particular, triboelectric nanogenerator-based tactile sensors have garnered significant interest, pursuing enhanced performance in material and texture recognition, coupled with simplicity in fabrication, cost-effectiveness, high resolution and sensitivity. Thus, in this work, we propose a flexible triboelectric tactile sensor, utilizing the freestanding single-electrode triboelectric nanogenerator principle, realizing concurrent material and texture detection in a single device. We leverage a novel hybrid operational regime for tactile sensing, combining the advantages of both contact-separation and surface sliding modes in a single contact-sliding-separation motion. This enables a realistic representation of the surface employing an artificial finger, by gathering material information from the contact-separation events and texture details from the sliding motion. Common materials such as wood, paper, copper and glass were used for the identification study along with textured surfaces made of the same materials with microscopic surface features. Simultaneous classification and recognition of materials and textures was performed by a single, 1D convolutional artificial neural network, achieving an average recognition accuracy of 98.4% across all different surfaces. [Display omitted] • Flexible triboelectric tactile sensor based on freestanding, single-electrode TENG for material and texture recognition. • Recognition of materials and texture under diverse applied forces on the surface • 1D Convolutional neural networks for simultaneous classification of material and texture. [ABSTRACT FROM AUTHOR]

Hydrogel-based stretchable ionic skins have attracted extensive attention as on-skin epidermal electronics owing to their inherent biocompatibility and ionic conductivity. However, the problem that water in traditional hydrogels eventually evaporates as exposed to air largely hinders their long-term sensing applications. Herein, we report an atmospheric moisture-digesting, biocompatible, and breathable zwitterionic skin with high environmental tolerance by introducing a super hygroscopic zwitterion-glycerylphosphorylcholine (GPC) into hydrogen-bonded polyacrylic acid network. The incorporation of GPC endows the zwitterionic skin with very high water-retaining ability (∼18.3 wt% water content at RH 20 %) and thus superior ambient stability more than one month and freezing resistance (freezing point ≈ −74 °C). Moreover, the multiple and reversible physical bonds in the matrix bring excellent stretchability and elastic recovery, good adhesion to various substrates, rapid self-healing, as well as moisture regeneration. The water-processable zwitterionic skin can also be used as conductive inks, utilizing its universal adhesion and adjustable rheology, to customize zwitterionic tattoos by painting or stencil printing, resulting in ultraconformal and seamless contact with irregular substrates. The zwitterionic skin with all these comprehensive advantages is demonstrated to function as a durable non-drying and self-adhesive sensing platform for multifunctional human-machine interfacing and artificial multimodal tactile sensors. [Display omitted] • Zwitterionic skin is prepared by combining polyacrylic acid with glycerylphosphorylcholine. • Zwitterionic skin has strong moisturizing, anti-freezing, and fast self-healing abilities. • Zwitterionic tattoos can be customized through painting or stencil printing. • Excellent epidermal sensors and artificial multimodal tactile sensors are demonstrated. [ABSTRACT FROM AUTHOR]

Our study reported herein aims to determine whether an electromagnetic field, induced triboelectrically by a metallic cone, rotating at a frequency of 167 Hz, has an effect on the properties of the horseradish peroxidase (HRP) enzyme. Atomic force microscopy (AFM) was employed to detect even the most subtle effects on single enzyme molecules. In parallel, a macroscopic method (spectrophotometry) was used to reveal whether the enzymatic activity of HRP in solution was affected. An aqueous solution of the enzyme was incubated at a distance of 2 cm from the rotating cone. The experiments were performed at various incubation times. The control experiments were performed with a non-rotating cone. The incubation of the HRP solution was found to cause the disaggregation of the enzyme. At longer incubation times, this disaggregation was found to be accompanied by the formation of higher-order aggregates; however, no change in the HRP enzymatic activity was observed. The results of our experiments could be of interest in the development of enzyme-based biosensors with rotating elements such as stirrers. Additionally, the results obtained herein are important for the correct interpretation of data obtained with such biosensors.

The present study is aimed at the revelation of subtle effects of steam flow through a conical coil heat exchanger on an enzyme, incubated near the heat exchanger, at the nanoscale. For this purpose, atomic force microscopy (AFM) has been employed. In our experiments, horseradish peroxidase (HRP) was used as a model enzyme. HRP is extensively employed as a model in food science in order to determine the influence of electromagnetic fields on enzymes. Adsorption properties of HRP on mica have been studied by AFM at the level of individual enzyme macromolecules, while the enzymatic activity of HRP has been studied by spectrophotometry. The solution of HRP was incubated either near the top or at the side of the conically wound aluminium pipe, through which steam flow passed. Our AFM data indicated an increase in the enzyme aggregation on mica after its incubation at either of the two points near the heat exchanger. At the same time, in the spectrophotometry experiments, a slight change in the shape of the curves, reflecting the HRP-catalyzed kinetics of ABTS oxidation by hydrogen peroxide, has also been observed after the incubation of the enzyme solution near the heat exchanger. These effects on the enzyme adsorption and kinetics can be explained by alterations in the enzyme hydration caused by the influence of the electromagnetic field, induced triboelectrically by the flow of steam through the heat exchanger. Our findings should thus be considered in the development of equipment involving conical heat exchangers, intended for either research or industrial use (including miniaturized bioreactors and biosensors). The increased aggregation of the HRP enzyme, observed after its incubation near the heat exchanger, should also be taken into account in analysis of possible adverse effects from steam-heated industrial equipment on the human body.

Diverse touch experiences offer a path toward greater human–machine interaction, which is essential for the development of haptic technology. Recent advances in triboelectricity‐based touch sensors provide great advantages in terms of cost, simplicity of design, and use of a broader range of materials. Since performance solely relies on the level of contact electrification between materials, triboelectricity‐based touch sensors cannot effectively be used to measure the extent of deformation of materials under a given mechanical force. Here, an ion‐doped gelatin hydrogel (IGH)‐based touch sensor is reported to identify not only contact with an object but also deformation under a certain level of force. Switchable ionic polarization of the gelatin hydrogel is found to be instrumental in allowing for different sensing mechanisms when it is contacted and deformed. The results show that ionic polarization relies on conductivity of the hydrogels. Quantitative studies using voltage sweeps demonstrate that higher ion mobility and shorter Debye length serve to improve the performance of the mechanical stimuli‐perceptible sensor. It is successfully demonstrated that this sensor offers dynamic deformation‐responsive signals that can be used to control the motion of a miniature car. This study broadens the potential applications for ionic hydrogel‐based sensors in a human–machine communication system. [ABSTRACT FROM AUTHOR]

• The mechanical energy of friction can be converted to degrading organic pollutants. • The tribocatalyic effect derived from the friction of the PFTE-sealed bar/Bi 2 WO 6 catalyst. • Bi 2 WO 6 exhibited efficient tribocatalytic activity and excellent durability. • Tribocatalysis can be improved by optimizing the friction area and the beaker material. Mechanical energy as the green and sustainable energy source widely distributes in natural environment. In this paper, we successfully realize the conversion of mechanical energy through a friction route on the tribocatalyst of Bi 2 WO 6. Under magnetic stirring, the friction between the PTFE-sealed magnetic bar and the catalyst particles resulted in the electron transfer crossing the contact interface, in which PTFE accepted the electrons and simultaneously the holes were left on the catalyst. The positively charged catalyst was demonstrated through electrostatic attraction and repulsion tests. Like photocatalytic process, the holes on the valence band of Bi 2 WO 6 have strong oxidative ability that can efficiently oxidize organic pollutants. The tribocatalytic tests showed that the Bi 2 WO 6 could eliminate organic dyes under magnetic stirring in dark, and we could further optimize the tribocatalytic performance via regulating the size of magnetic bar and reactor material. Finally, a high stability of tribocatalysis was revealed by the multiple tests. This work not only develops a green tribocatalysis strategy to oxidative purification of organic pollutants, but also provides a possible pathway to convert mechanical energy in environment to chemical energy, such as potential applications in environmental remediation and sustainable energy. [ABSTRACT FROM AUTHOR]

Developing nanogenerators (NGs) is achieved by exploiting the piezoelectric, triboelectric, and pyroelectric effects of both organic and inorganic materials. Many exhibit beneficial electrical properties (dielectric, conductive, or insulating) or have surfaces that are polarizable upon friction or physical contact. Recently, biomass‐derived materials and recycled materials, whose electrical activity can be induced, are explored for application in the design of more sustainable, cost‐effective, biodegradable, disposable NGs, and have demonstrated a wide range of output (microenergy) power densities. Among them, cellulose, the most abundant biopolymer, is found to offer excellent opportunities for designing and manufacturing NGs with multifunctional capacities. Cellulose can be derived into varied forms with multifunctionalities and physical morphologies. This account provides an overview of how cellulose is utilized in creating NGs based on piezoelectric, triboelectric, and pyroelectric effects. Because the mechanical properties of cellulose are tunable, current research trends on NGs originate with the triboelectric effect. The discussion here focuses on design, fabrication methods, achievable electrical power output, and combinations with other materials and devices. Challenges in efficient fabrication and consistent power densities, and opportunities for integrating different technologies and developing more sustainable (in terms of economic, environmental, and ecological) nature–human–machine interfacial devices are also discussed. [ABSTRACT FROM AUTHOR]

Cardiovascular disease (CVD) remains the leading cause of death worldwide. Patients often fail to recognize the early signs of CVDs, which display irregularities in cardiac contractility and may ultimately lead to heart failure. Therefore, continuously monitoring the abnormal changes in cardiac contractility may represent a novel approach to long-term CVD surveillance. Here, a zero-power consumption and implantable bias-free cardiac monitoring capsule (BCMC) is introduced based on the triboelectric effect for cardiac contractility monitoring in situ. The output performance of BCMC is improved over 10 times with nanoparticle self-adsorption method. This device can be implanted into the right ventricle of swine using catheter intervention to detect the change of cardiac contractility and the corresponding CVDs. The physiological signals can be wirelessly transmitted to a mobile terminal for analysis through the acquisition and transmission module. This work contributes to a new option for precise monitoring and early diagnosis of CVDs., (© 2024 Wiley‐VCH GmbH.)

Abstract In terms of advances in technology, especially electronic devices for human use, there are needs for miniaturization, low power, and flexibility. However, there are problems that can be caused by these changes in terms of battery life and size. In order to compensate for these problems, research on energy harvesting using environmental energy (mechanical energy, thermal energy, solar energy etc.) has attracted attention. Ferroelectric materials which have switchable dipole moment are promising for energy harvesting fields because of its special properties such as strong dipole moment, piezoelectricity, pyroelectricity. The strong dipole moment in ferroelectric materials can increase internal potential and output power of energy harvesters. In this review, we will provide an overview of the recent research on various energy harvesting fields using ferroelectrics. A brief introduction to energy harvesting and the properties of the ferroelectric material are described, and applications to energy harvesters to improve output power are described as well.

Abstract Long-term observation of the triboelectric effect has not only proved the feasibility of many novel and useful tribo-devices (e.g., triboelectric nanogenerators), but also constantly motivated the exploration of its mysterious nature. In the pursuit of a comprehensive understanding of how the triboelectric process works, a more accurate description of the triboelectric effect and its related parameters and factors is urgently required. This review critically goes through the fundamental theories and basic principles governing the triboelectric process. By investigating the difference between each charging media, the electron, ion, and material transfer is discussed and the theoretical deduction in the past decades is provided. With the information from the triboelectric series, interesting phenomena including cyclic triboelectric sequence and asymmetric triboelectrification are precisely analyzed. Then, the interaction between the tribo-system and its operational environment is analyzed, and a fundamental description of its effects on the triboelectric process and results is summarized. In brief, this review is expected to provide a strong understanding of the triboelectric effect in a more rigorous mathematical and physical sense.

Featured Application: The effect of an electromagnetic field, induced upon the motion of glycerol through polymeric pipes, on the aggregation state and functional activity of enzymes should be taken into account in the development of novel highly sensitive biosensor systems intended for studying structural and functional features of enzymes. The effect observed herein should also be considered in studying hemodynamics in human body. Flow-based coiled systems, through which a heat transfer fluid (such as glycerol) is pumped, are widely used for thermal stabilization of bioreactors and biosensor cuvettes and cells. Previously, using horseradish peroxidase (HRP) as a model protein, we have demonstrated that the incubation of a protein solution in a flow-based system over coiled pipe with flowing glycerol leads to a change in the adsorption properties of the protein macromolecules. Herein, we have studied the effect of the glycerol flow on the properties of HRP, the solution of which was placed differently: i.e., near either the inflow or the outflow linear sections of the pipe, while the coiled section of the pipe was shielded with a grounded metallic cover. Atomic force microscopy (AFM) has been employed in order to visualize the HRP protein macromolecules adsorbed from its solution onto the mica substrate surface. The quantity of adsorbed protein was estimated based on the AFM data. The enzymatic activity of HRP was estimated by spectrophotometry. We demonstrate that a change in the properties of HRP enzyme was observed after the incubation of its solution near the inflow/outflow linear sections of the pipe with flowing glycerol. Namely, after the incubation of HRP solution near the inflow section, a decrease in the protein adsorption onto mica was observed, but its enzymatic activity remained unchanged in comparison to the control sample. In another case, when the HRP solution was incubated near the outflow section, an increased protein adsorption was observed, while the enzyme exhibited considerably lower activity. [ABSTRACT FROM AUTHOR]

Friction energy is well-known common clean energy and can be harvested via triboelectricity. In this study, hydrothermally synthesized zinc oxide nanorods exhibit excellent tribo-catalytic dye decomposition performance via harvesting friction energy, which is obtained by stirring. After 60 h of stirring, tribo-catalytic dye decomposition ratio is as high as ~ 99.8%. Strong tribo-catalytic performance can be ascribed to the triboelectric effect, which originates from the friction between zinc oxide nanorods and stirring rods. Intermediate active species hydroxyl radicals are further observed via fluorescence method, in which the number of hydroxyl radicals continuously increases with increasing stirring time. Besides, zinc oxide nanorods also exhibit good recycling utilization property after three consecutive catalytic experiments. Strong tribo-catalytic performance and good recycling utilization property of zinc oxide nanorods make it potential in utilizing friction energy in our environment to achieve dye wastewater purification in near future. Image 1 [ABSTRACT FROM AUTHOR]

The aim of the study was to assess the effectiveness of the electrostatic separation on fractionation and deconstruction of the grape stalks lignocellulosic biomass. After the measurements of their physical properties, the eight fractions obtained were extracted with hot water and then with hot 2% sulphuric acid. In aqueous extracts, the concentrations of glucose and fructose of samples collected in the jars under the positive electrode were as high as 13.5 and 11.6 g/100 g d.w., respectively. As for acid hydrolysis, the concentration of furfural and HMF were 1996-2600 and 144-291 mg/kg d.w., respectively. The results showed the opportunity of using grape stalks as a source of fermentable sugars, as well as a potential source of furanic compounds. This technique can represent a new and affordable method of lignocellulosic biomass pre-treatment which can easily be integrated into a biorefinery to favour partial fractionation and better exposure of the fractions to a subsequent enzymatic or chemical attack. © 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved. [ABSTRACT FROM AUTHOR]

Van de Graaff generator is a simple but very useful, electrostatic generator which is able to accumulate electric charge on a hollow metal sphere. It’s only made of moving belt, rollers, motor, and copper brushes. The goal is to show that the experiment could be performed by talented elementary student with help from his teacher and meant for the physics classroom in any high school around the world. [ABSTRACT FROM AUTHOR]

Flexible materials with high electromechanical coupling performance are highly demanded for wide applications for electromechanical sensors and transducers, including mechanical energy harvesters. Here, outstanding electromechanical performance is obtained in electrospun‐aligned polyvinylidene fluoride (PVDF) fiber film. A theoretical model is developed from systematic theoretical analyses to clarify the underlying constructive piezoelectric‐triboelectric mechanism in the polarized PVDF fiber films that explains the experimental observations well. The electrospinning process induces polarization alignment and thus tunes the electron affinity for PVDF fibers with different polarization terminals, which results in the constructive piezoelectric and triboelectric responses in the obtained PVDF fiber films. Extremely large effective piezoelectric performance properties are achieved in the direct piezoelectric measurements, reaching the maximum effective piezoelectric strain and voltage coefficients of −1065 pm V−1 and −9178 V mm N−1, respectively, at 100 Hz. In the converse piezoelectric measurements without a significant contribution from reversible triboelectric effect, the maximum effective piezoelectric strain and voltage coefficients are −166 pm V−1 and −1499 V mm N−1, respectively. The theoretical analyses and experimental results show the great potential of the electrospun aligned polar PVDF fiber material for various electromechanical device applications, particularly for mechanical energy harvesting. [ABSTRACT FROM AUTHOR]

Electronic noses, inspired by the mammalian olfactory system, have revolutionized various industries including food, environment, medicine, and rescue. They detect gases by using sensor arrays and provide real-time information. However, current electronic noses demand batteries as the power source, limiting their applications and requiring frequent maintenance. Wireless transmitter modules can also increase battery dependence and introduce high energy consumption. Moreover, gas sensors used in electronic noses lack multidimensional information identification ability. Here, we have developed a self-powered, wireless electronic nose system based on triboelectric discharge. By converting mechanical energy into high-voltage power, this system can initiate gas discharge and produce wireless signals that contain valuable gas information. With deep learning, it can recognize up to 60 different types of gas atmospheres with 93.8% accuracy, including 5 gas components with 12 different gas pressures. The system with a visualization program is designed for wireless, real-time gas monitoring toward applications in health monitoring, precise manufacturing, and high-tech fire rescue operations. [Display omitted] • The self-powered electronic nose, enabled by triboelectric discharge, demonstrates the ability to detect 60 different gas conditions. • Analyze the relationship between the triboelectric discharge current and wireless signal. • The electronic nose could act as an automated, visualized, real-time gas sensing platform, by integrating deep learning and visualization programs. [ABSTRACT FROM AUTHOR]

In this review, the concept of a hybrid solar cell system, called all-weather solar cells, a new view on energy harvesting device design, is introduced and described in detail. Additionally, some critical economical, technological, and ecological aspects are discussed. Due to drastic global climate changes, traditional energy harvesting devices relying only on solar energy are becoming less adaptive, hence the need for redesigning photovoltaic systems. In this work, alternative energy harvesting technologies, such as piezoelectric and triboelectric devices, and photoelectron storage, that can be used widely as supporting systems to traditional photovoltaic systems are analysed in detail, based on the available literature. Finally, some examples of all-weather solar cells composed of dye-sensitized solar cells (DSSC) and silicon solar cells, often modified with graphene oxide or phosphors materials, as new perspective trends in nanotechnology are presented. Two types of solar cell triggers are analysed: (i) solar cells working during day and night (DSSC with phosphors materials), and (ii) solar cells working under sun and rain conditions (piezoelectric and triboelectric silicon or DSSC solar cells).

Triboelectric nanogenerators (TENGs) have emerged as a promising technology for harvesting mechanical energy from the ambient environment. However, developing tribopositive materials with strong piezoelectric effects and high electron-donating ability still remains a challenge. Herein, poly(ethylene glycol) monomethyl ether (mPEG) to soft poly(lactic acid) (PLA) is adopted, then PLA/mPEG nanofibers are fabricated under electrospinning and used as the tribopositive material for fabricating robust power density TENGs. The crystallinity and dynamic mechanical properties of PLA/mPEG nanofibers are investigated. The results revealed that the incorporation of mPEG provided an effective approach to elevate the electron-donating ability and charge transfer efficiency in PLA. The PLA/mPEG-based TENGs achieved a high open-circuit voltage of 342.8 V, a short-circuit current of 38.5 µA, and a maximum power density of 116.21 W m -2 over a 2 cm 2 contact area at an external load of 10 6  Ω, respectively. Strikingly, excellent stability and durability are demonstrated after continuous cycles up to 10 4 cycles. Noteworthy, the TENGs are explored for self-powered sensing applications, with seven TENG units integrated to act as self-powered sensors playing music through buzzers when pressed by fingers. Eventually, this work provides new insights into tuning the structures and properties of electrospun polymers to reinforce the TENG output and self-powered systems., (© 2023 Wiley‐VCH GmbH.)