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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]

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.)

Self-powered wireless sensor systems have emerged as an important topic for condition monitoring in nuclear power plants. However, commercial wireless sensor systems still cannot be fully self-sustainable due to the high power consumption caused by excessive signal processing in a mini-electronic computing system. In this sense, it is essential not only to integrate the sensor system with energy-harvesting devices but also to develop simple data processing methods for low power schemes. In this paper, we report a patch-type vibration visualization (PVV) sensor system based on the triboelectric effect and a visualization technique for self-sustainable operation. The PVV sensor system composed of a polyethylene terephthalate (PET)/Al/LCD screen directly converts the triboelectric signal into an informative black pattern on the LCD screen without excessive signal processing, enabling extremely low power operation. In addition, a proposed image processing method reconverts the black patterns to frequency and acceleration values through a remote-control camera. With these simple signal-to-pattern conversion and pattern-to-data reconversion techniques, a vibration visualization sensor network has successfully been demonstrated.

The manuscript introduces the use of non-electrically polled spin-coated thin polyvinylidene fluoride (PVDF) films as the active layers in a contact electrification-based nanoenergy harvester. The four-layered device utilizes both piezo and triboelectric effect coupled with electrostatic induction. The elucidation of potential generation during contact between crystalline phases (α and β) of PVDF layer material is investigated in the manuscript. Fourier transform infrared–attenuated total reflectance spectroscopy is carried out to illustrate the α - and β -phases in PVDF pellet, prepared film as well as the film after contact. Dynamic contact mode electrostatic force microscopy (DC-EFM) along with atomic force microscopy is used for the evaluation of reverse piezoelectric, local ferroelectric, triboelectric voltage and adhesive energy of the PVDF films before–after contact process. Quantum chemical calculation is performed using density functional theory to explain possible electron transitions in the active layers between the cylindrically symmetric α -phase and electrical double layer charges in the β -phase of PVDF. The interface study of the film is also carried out both experimentally using DC-EFM and through quantum chemical calculations. The fabricated device with the hybrid piezo-tribo layer promises to be a simple and low-cost energy source for the next-generation self-powered electronic devices. The device can also be used as knock sensor in engines as well as a capacitor. [ABSTRACT FROM AUTHOR]

This paper describes the effect of oscillatory frequencies caused by ocean wave impact on the output performance of dielectric-metal contact separation mode triboelectric nanogenerators (DMCS-TENG). The triboelectric effect is generated as a result of regular, non-uniform contact between a dielectric layer which gains electrons (negative triboelectric material) and a conductive layer that loses electrons (positive triboelectric material). Impact testing was used to characterize arc-shaped dielectric-metal single electrode triboelectric nanogenerators (DMSE-TENG) with different triboelectric material combinations based on their output power generation, using a 40-mm ball bearing to apply a 12-N force impulse. It was found that the best dielectric-conductor combination for the DMCS-TENG performance was polyimide and PDMS in contact with the conductor layers of aluminum and silver conductive cloth tape. Therefore, in the range of operation from 30 to 300 Hz with an amplitude acceleration of 319.62 to 559.29 mm/ $\text{s}^{{2}}$ , the maximum generated output power, power density, and total energy conversion efficiency of the device, made with polyimide and honeycomb patterned aluminum foil, can reach up to $778.43~\mu \text{W}$ , $12.16~\mu \text{W}$ /cm $^{{2}}$ , and 15.85 % respectively, for a load resistance of 10 $\text{M}\Omega $. The output power performance of the DMCS-TENG shows an enhancement by a factor of 2.3 with a honeycomb-patterned aluminum foil, by increasing the surface charge density between the layers in contact, relative to flat aluminum foil. Additionally, through the integration of the energy harvester prototype into a water wave generator tank, an output power density of 169.218 mW/ $\text{m}^{{2}}$ was reached, where it is expected to generate output power energy around 3.05 W, over an area of 18 $\text{m}^{{2}}$ with wave sizes among 0.3 to 4 m. This paper demonstrates that the device can function as an energy harvesting mechanism for ocean wave sensing applications that require self-powering. [ABSTRACT FROM AUTHOR]

For mechanical equipment or facilities, abnormal vibration and external impact can sometimes cause fatigue or even failure, which might lead to severe accidents. It's necessary to monitor the movement of important devices during their service and identify these abnormal conditions. In recent years, triboelectric nanogenerators (TENGs) have been widely used for collecting energy in many applications, and many experiments show that it is an effective method for self-powered sensing. In this paper, a mathematical model of a novel self-powered eccentric triboelectric nanosensor (Ec-TENS) has been built which can detect linear acceleration and velocity. Governing equations between output voltage and linear acceleration/velocity have been derived. Based on the theoretical model, a sliding-mode prototype has been designed and fabricated to verify the theoretical models through a series of tests. Experimental results have shown that Ec-TENS could generate output voltage once external acceleration exceeds a threshold, and amplitude of voltage could vary with velocity. The output voltage and linear velocity satisfy a specific function, and have a good repeatability and stability. Because of its self-powered feature, the novel Ec-TENS has potentially wide applications in the fields of structural health monitoring (SHM), wearable devices, security systems and aeronautic fields, especially in extreme environmental or unattended conditions. Image 1 • Proposed a novel design of a self-powered eccentric triboelectric nanosensor. • Proposed a theoretical model, governing equations and verified them by tests. • It can detect linear velocity and acceleration change without a power supply. [ABSTRACT FROM AUTHOR]

We present a new concept for impact-based triboelectric nanogenerators (TENG) inspired from the electrostatic machines of the 18th century. With this system, the electrical energy converted from the mechanical domain is automatically accumulated in a large capacitance without the need of diodes. Our TENG has three electrodes and self-synchronized/self-actuated mechanical switches, which automatically and repeatedly connect the capacitances of the system according to their series and parallel configurations in order to reproduce a behaviour similar to the Bennet's charge doubler. The movable and freestanding electrode is covered with triboelectric patches that drastically decreases the start-up time. The output voltage, and so the harvested energy, increases exponentially until either the output voltage reaches the air dielectric breakdown or a saturation occurs because the electrostatic forces become comparable to the mechanical ones. We have developed a complete numerical model that takes into account both electrical and mechanical forces and is able to show the saturation phenomena due to the high electromechanical coupling occurring at high voltage. This model has been validated with practical experiments where the prototype were excited with a sinusoidal acceleration of 0.2 g rms at 5 Hz. This new and diode-free concept can be applied to any TENG having at least one variable capacitor to boost the mechanical-to-electrical energy conversion. We report a new type of triboelectric nanogenerator (TENG) having alternating and self-actuated series-to-parallel interfaces based on self-synchronized mechanical switches. It has been inspired from the Bennet doubler electrical machine. The TENG is composed of a freestanding electrode, two anti-phase variable capacitors excited by the external vibrations, and a reservoir capacitor. The absence of diodes and their unavoidable voltage threshold for signal rectification, combined with the boost introduced by the Bennet-like doubler structure, can largely improve the energy conversion efficiency of TENGs, especially during the start-up. Image 1 • We report a new TENG having a self-actuated series-to-parallel electrical interface based on mechanical switches. • The absence of diodes combined with the Bennet-like doubler can largely improve the energy conversion efficiency of TENGs. • A numerical model that takes into account both electrical and mechanical forces has been validated with the experiments. [ABSTRACT FROM AUTHOR]

Sensors based on triboelectric nanogenerators have been widely used for energy harvesting and sensing applications, however, the applications of multidimensional information perception and interactive control are insufficient. In this paper, we present an ultra-stretchable triboelectric strip sensor (TSS) using triboelectric mechanism for controlling the objects in three-dimensional space. This facile and low-cost TSS is mainly composed of a parallel structure including three symmetric sensor strips fixed on the base and a mobile stage connected with them. Based on the coupling effect of triboelectrification and electrostatic induction, the length changes of each strip with the same finger contacting point generate different signal output ratios from two terminal electrodes, functioning as the interactive interface for multi-dimensional sensing and controlling. Hence, the parallel sensor strips structure can realize the sensing and controlling in three degrees of freedom of linear motion and two degrees of freedom of rotational motion, and resultant sensing ranges are X, Y, Z, α and β (20 mm, 20 mm, 30 mm, 36°, and 36°). In terms of manipulation, this is simpler than the conventional controller with rigid structure and includes additional space dimensions. Furthermore, demonstration of the TSS as human-nanomachine terminal to control the nanomanipulator in scanning electron microscope (SEM) is successfully realized with the accuracy of 10 nm. The proposed TSS shows great potential for the applications in automated control, robotics control, and Internet of Things (IoT). Image 1 • A control terminal based on triboelectric mechanism is designed to control the attitudes of the object. • The parallel sensor strips structure can realize the sensing and controlling in five degrees of freedom. • The control terminal TSS realizes the operating of carbon nanotubes in SEM. [ABSTRACT FROM AUTHOR]

Sprays are widely distributed in nature and industry, but how to convert the energy inherent in sprays into electricity in an efficient and low-cost way is challenging. Herein, we demonstrated a new type of triboelectric nanogenerator for spray energy harvesting (S-TENG). By exploiting the triboelectric effect between the spray droplets and the polytetrafluoroethylene (PTFE) tube surface, the S-TENG can produce an open-circuit voltage of up to 240 V and a short-circuit current of up to 15 μA. The dependence of output performance on the tube length, wall thickness, tube diameter, spray pressure, tube material, and liquid type was systematically investigated. In addition, the S-TENG can successfully harvest spray energy to light up 21 commercial LEDs or power a calculator. The results provide an innovative approach for spray energy harvesting and new research directions for liquid-solid triboelectric nanogenerators (LS-TENG). [Display omitted] • A novel triboelectric nanogenerator was developed for spray power generation. • The S-TENG can produce a voltage of 240 V by exploiting the triboelectric effect. • Extensive investigation of parameters on generator's output performance. • The S-TENG can harvest energy from sprays and light up 21 commercial LEDs. [ABSTRACT FROM AUTHOR]

Titanium-based (Ti-based) nanowire scaffolds are advantageous for promoting cell growth and facilitating tissue regeneration. In addition to the presence of open pores and channels within these scaffolds, it is essential to investigate potential profound underlying mechanisms that contribute to the favorable effects of nanowire scaffolds cell growth. In this study, we found that Ti-based nanowire scaffolds exhibit dynamic tribo-mechanical responsive behavior varying with the number and amplitude of nano-deformation cycles can promote the growth of osteoblasts in culture in vitro. We also found that the scaffolds with strong tribo-mechanical responsive behavior exhibited superior osteoblasts growth compared to the scaffold with weak tribo-mechanical responsive behavior. This work involves the establishment of well-defined interactions between tissues and implants, particularly in relation to tribo-mechanical response conditions. [ABSTRACT FROM AUTHOR]

Theoretical models have been proposed to bring an in-depth understanding of the working mechanisms of triboelectric nanogenerators (TENGs), aiming to enhance their output performance. This work proposes an enhanced distance-dependent electric field (EDDEF) model to predict triboelectric characteristics of TENGs more accurately. The model bridges the gap between the distance-dependent and distance-independent electric field models in terms of open-circuit (OC) voltage (V OC), short-circuit (SC) voltage (V gap , SC), and SC surface charge density (σ SC) at small separation distances by developing more accurate mathematical formulations of the electric potential. The EDDEF model was validated by finite element modeling (FEM) simulation. It introduced an accurate theoretical analysis of the air-breakdown boundary under the OC condition for the first time. The maximum surface charge density that can be obtained without air breakdown was predicted to be lateral size-dependent. It shows a monotonical decrease from 51.94 to 33.59 µC/m2 with a lateral size increase from 0.5 to 10 cm. Meanwhile, the corresponding separation distance increased from 0.915 to 12.48 mm, suggesting that improving CS-TENG's performance by boosting the surface charge density is more effective at smaller lateral sizes and shorter separation distances. These findings serve as a guide towards the miniaturization of highly efficient CS-TENG technology. In addition, under SC condition, the EDDEF model showed great consistency with the distance-independent model in predicting the air-breakdown limit, supporting the distance-independent model applicability for predicting the air-breakdown under the CS condition. [Display omitted] • This work bridges the gap between distance-dependent and distance-independent electric field models at a small separation. • This model proposed an accurate theoretical analysis of the air-breakdown limit under OC condition for the first time. • Under OC condition, the maximum surface charge density decreases with increasing the lateral size of the CS-TENG. • This model is consistent with distance-indpendent electric field model under short-circuit condition. [ABSTRACT FROM AUTHOR]

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.

Atomic force microscopy (AFM)-based fishing is a promising method for the detection of low-abundant proteins. This method is based on the capturing of the target proteins from the analyzed solution onto a solid substrate, with subsequent counting of the captured protein molecules on the substrate surface by AFM. Protein adsorption onto the substrate surface represents one of the key factors determining the capturing efficiency. Accordingly, studying the factors influencing the protein adsorbability onto the substrate surface represents an actual direction in biomedical research. Herein, the influence of water motion in a flow-based system on the protein adsorbability and on its enzymatic activity has been studied with an example of horseradish peroxidase (HRP) enzyme by AFM, attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) and conventional spectrophotometry. In the experiments, HRP solution was incubated in a setup modeling the flow section of a biosensor communication. The measuring cell with the protein solution was placed near a coiled silicone pipe, through which water was pumped. The adsorbability of the protein onto the surface of the mica substrate has been studied by AFM. It has been demonstrated that incubation of the HRP solution near the coiled silicone pipe with flowing water leads to an increase in its adsorbability onto mica. This is accompanied by a change in the enzyme’s secondary structure, as has been revealed by ATR-FTIR. At the same time, its enzymatic activity remains unchanged. The results reported herein can be useful in the development of models describing the influence of liquid flow on the properties of enzymes and other proteins. The latter is particularly important for the development of biosensors for biomedical applications—particularly for serological analysis, which is intended for the early diagnosis of various types of cancer and infectious diseases. Our results should also be taken into account in studies of the effects of protein aggregation on hemodynamics, which plays a key role in human body functioning.

Highly efficient air filtration with low pressure drop is the key to air purification. In this work, a self-powered electrospun nanofiber membrane with an electrostatic adsorption effect was prepared to improve the filtration efficiency of micro/nano particles. The composite membrane was comprised of polyvinyl chloride (PVC) nanofibers and polyamide-6 (PA6) nanofibers. The triboelectric effect between the two adjacent nanofiber membranes generated electrostatic charges under the action of air vibration, by which the electrostatic adsorption with the same pressure drop was enhanced. The electrostatic voltage on the self-powered nanofiber membrane was 257.1 mV when the flow velocity was 0.1 m/s. For sodium chloride (NaCl) aerosol particles with a diameter of 0.3 μm, the removal efficiency of the self-powered composite nanofiber membrane was 98.75% and the pressure drop was 67.5 Pa, which showed a higher quality factor than the membrane without electrostatic charges. This work provides an effective way to improve the filtration performance of air filter membranes.

Nowadays, energy-related issues are of paramount importance. Every energy transformation process results in the production of waste heat that can be harvested and reused, representing an ecological and economic opportunity. Waste heat to power (WHP) is the process of converting the waste heat into electricity. A novel approach is proposed based on the employment of liquid nano colloids. In this work, the triboelectric characterization of TiO2 nanoparticles dispersed in pure water and flowing in a fluorinated ethylene propylene (FEP) pipe was conducted. The idea is to exploit the waste heat to generate the motion of colloidal TiO2 through a FEP pipe. By placing an Al ring electrode in contact with the pipe, it was possible to accumulate electrostatic charges due to the triboelectric effect between the fluid and the inner pipe walls. A peristaltic pump was used to drive and control the flow in order to evaluate the performances in a broad fluid dynamic spectrum. The system generated as output relatively high voltages and low currents, resulting in extracted power ranging between 0.4 and 0.6 nW. By comparing the power of pressure loss due to friction with the extracted power, the electro-kinetic efficiency was estimated to be 20%.

Pain sensation is a crucial aspect of perception in the body. Force-activated nociceptors encode electrochemical signals and yield multilevel information of pain, thus enabling smart feedback. Inspired by the natural template, multi-dimensional mechano-sensing materials provide promising approaches for biomimetic nociceptors in intelligent terminals. However, the reliance on non-centrosymmetric crystals has narrowed the range of these materials. Here centrosymmetric crystal Cr 3+ -doped zinc gallogermanate (ZGGO:Cr) with multi-dimensional mechano-sensing is reported, eliminating the limitation of crystal structure. Under forces, ZGGO:Cr generates electrical signals imitating those of neuronal systems, and produces luminescence for spatial mapping of mechanical stimuli, suggesting a path toward bionic pain perception. On that basis, a wireless biomimetic nociceptor system is developed and a smart pain reflex in a robotic hand and robot-assisted biopsy surgery of rat and dog is achieved., (© 2023 Wiley-VCH GmbH.)

As an advanced sensing technology, dual-mode flexible sensing, integrating both tactile and touchless perception, propels numerous intelligent devices toward a more practical and efficient direction. The ability to incorporate multiple sensing modes and accurately distinguish them in real time has become crucial for technological advancements. Here, we proposed a dual-mode sensing system (B-MIGS) consisting of a dual-layer sensing device with a magnetically induced grid structure and a testing device. The system was capable of utilizing mechanical pressure to perceive tactile stimulation and magnetic sensing to simultaneously transduce touchless stimulation simultaneously. By leveraging the triboelectric effect, the decoupling of tactile and touchless signals in the presence of unknown signal sources was achieved. Additionally, the sensing characteristics of the B-MIGS were optimized by varying the curing magnetic induction intensity and magnetic particle concentration. The influence of the temperature and humidity on the sensing signals was also discussed. Finally, the practical value of the B-MIGS as a dual-mode monitoring system was demonstrated on soft petals and sensor arrays, along with exploration of its potential application in underwater environments.

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. [ABSTRACT FROM AUTHOR]

Wearable electronics are believed to be the future of the next-generation electric devices. However, the comfort of current wearable devices is greatly limited due to the use of airtight materials, which may even lead to inflammation of the skin. Therefore, breathable, skin-friendly materials, are highly desired for wearable devices. Here, the recent progress of the breathable materials used to fabricate skin-friendly electronics is reviewed by taking triboelectric effect-based wearable electronics as a typical example. Fibers, yarns, textiles, and nanofiber membranes are the most popular dielectric materials that serve as frictional materials. Metal mesh, silver yarn, and conductive networks made up of nanomaterial are preferred as air-permissive electrodes. The breathable materials for skin-friendly wearable electronics summarized in this review provide valuable references for future fabrication of humanized wearable devices and hold great significance for the practical application of wearable devices. [ABSTRACT FROM AUTHOR]

Triboelectric nanogenerators and sensors have been widely adopted for diversified energy harvesting and sensing applications, but the demonstrations of 3D information sensing and controlling are very limited. In this paper, we present a novel self-powered virtual reality 3D-control sensor (VR-3D-CS) based on triboelectric mechanism for controlling the attitude (both the position and rotation) of object in 3D virtual space. This innovative, cost-effective, simple-designed sensor has a symmetric 3D structure with eight separated sensing electrodes and two touching spheres as the interactive interface with human fingers for 3D force information sensing and VR controlling. Based on the coupling effect of triboelectrification and electrostatic induction, the VR-3D-CS generates different electric output signals in response to different operation manner that can be used to control the attitude of objects in 3D virtual space. The symmetrical 3D configuration design of the sensor enables the detection of 3D force from both the normal direction and shear direction. By employing vector properties of force and signal analysis from the eight sensing electrodes, detection of six-axis directions in 3D space is achieved by triboelectric mechanism for the first time. The VR-3D-CS has been demonstrated to be able to detect normal force in the range of 0–18 N. It can resolve the shear force direction with step resolution of at least 15°. Besides, due to the positive output voltage and low internal impedance, the VR-3D-CS is readily compatible with commercial portable signal processing system for signal analysis and controlling. Demonstration of the VR-3D-CS as interactive interface for Augmented Reality (AR) control is successfully realized. The robust structure, stable output performance and self-powered sensing property enable the device as an ideal human machine interface towards AR interface, batteryless and energy saving applications. [ABSTRACT FROM AUTHOR]

Harvesting mechanical energy and effectively converting it into electrical power by triboelectric nanogenerators (TENGs) have been demonstrated as a burgeoning field of research, that can be essential for the energy of the new era, which is the era of internet of things, big data, and artificial intelligence. Here the structural figure-of-merits (FOM S ) for quantitatively evaluating and comparing the output performance of TENGs under different load resistances are studied. Firstly, we introduce the triboelectric process and transient process to analyze the charges transfer in each half cycle. Because each process corresponds to a first-order differential equation, four basic governing equations in a whole cycle are built up. After solving these equations, the real-time output characteristics of TENG are demonstrated, which comprehensively reveal the output behavior of TENG devices. Then, same method is utilized to investigate the maximum harvested energy and structural FOM RS with different load resistances at various maximum displacements. These theoretical results especially about the derived FOM RS provide an improved capability of comparing different configurations of TENGs. This work can not only completely explain the working principles of TENGs, but also enhance the applicability of structural FOM RS , enabling more efficient design and optimization of various TENG structures in practical applications. [ABSTRACT FROM AUTHOR]

The impact of design and external parameters on the intrinsic output properties and load characteristics of hybrid energy harvesting generator is significant in both designing the generator and power management circuit and achieving high energy conversion efficiency. In this work, the intrinsic output characteristics of a hybrid triboelectric and piezoelectric generator is investigated, where the impacts of design parameters on the output properties and load characteristics under resistive and capacitive load conditions are demonstrated using a wide-ranging setting of the design parameters and compared with the theoretical calculations using a parallel hybrid model. The regularities concluded from the experimental results reflect the actual output behavior of a typical hybrid generator and provide evidence that the parameters have significant impacts on the intrinsic output properties, resistive load behavior and charging behavior. The outcomes of this study can be used as guidance toward designing effective structures and power management as well as in future simulation of a wide range of hybrid generators. [ABSTRACT FROM AUTHOR]

Triboelectric nanogenerator (TENG) as a powerful mechanical energy harvesting technology has major applications as micro/nano-power source, for self-powered sensors and even large-scale blue energy, which would impact the world likely development for the future. In this work, a theoretical model for the sliding-mode TENG with considering the external force applied onto the TENG was presented. Through approximate analytical equations derivation, the output characteristics of TENG with arbitrary load resistance were calculated, including the output power and energy. Based on the relationships between the output characteristics and load resistance or sliding velocity, the force applied on the sliding component of TENG and the friction force were investigated for two cases, i.e. , without load resistor and with load resistor. Also, the influences of the resistance and sliding velocity on the forces were investigated. Furthermore, the corresponding experiments were carried out to measure the force applied on the TENG as well as the output performance of the fabricated sliding-mode TENG. The experimental results are in good agreement with the theoretical predictions, which can effectively reveal the principle of applied force on the TENG and facilitate the understanding of the relationship between the power, energy and applied force. [ABSTRACT FROM AUTHOR]

Here, we present a fully biodegradable triboelectric nanogenerator (BD-TENG) based on gelatin film and electrospun polylactic acid nanofiber membrane. By optimizing the material properties of the gelatin and PLA polymer films, an output voltage up to 500 V, a short circuit current density of 10.6 mA/m 2 and a maximum power density over 5 W/m 2 are achieved with a device dimension of 4 × 4 cm 2 . Performance of the BD-TENGs using different material combinations under various test conditions are investigated and analyzed. The BD-TENGs show excellent mechanical stability and reliability upon cyclical contact for up to 15,000 times. Biodegradation experiments show that all the materials of the TENG could be degraded completely into water in about 40 days. The BD-TENGs provide a promising green micro-power source for environment monitoring, biomedical implants through harvesting energy from wind, heart motion et al., yet they can dissolve with no adverse effect to environment or human body. [ABSTRACT FROM AUTHOR]