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The ability to detect multidimensional forces is highly desired for electronic skin (E-skin) sensors. Here, based on single-electrode-mode triboelectric nanogenerators (S-TENGs), fully elastic E-skin that can simultaneously sense normal pressure and shear force has been proposed. With the hemispherical curve-structure design and further structural optimization, the pressure sensor exhibits a high linearity and sensitivity of 144.8 mV/kPa in the low-pressure region. By partitioning the lower tribolayer into two symmetric parts, a multidimensional force sensor has been fabricated in which the output voltage sum and ratio of the two S-TENGs can be used for normal pressure and shear force sensing, respectively. When the multidimensional force sensors are mounted at a two-fingered robotic manipulator, the change of the grabbing state can be recognized, indicating that the sensor may have great application potential in tactile sensing for robotic manipulation, human-robot interactions, environmental awareness, and object recognition.

Exploring a rapid, reliable, and practical means to detect blockages and leakages in liquid pipelines and accurately locate their positions is of great importance in practical engineering applications. Here, we report a bubble motion-based triboelectric sensor (BM-TES) for detecting and locating the blockages and leaks inside a plastic tube. This simple-designed, environment-friendly, non-damaging sensor is composed of several ring-shaped Cu electrodes distributed on a polytetrafluoroethylene tube. The self-powered movement of the bubble under the action of buoyancy makes the inner wall of the tube change from the original solid-liquid phase to the gas-solid-liquid phase, which results in a short-term contact and separation between the liquid and the wall. Based on the fractional triboelectric effect of the liquid-solid contact, an obvious real-time stable voltage peak will be generated where the detection bubble passes. The obvious peaks of the open-circuit voltage with respect to time correspond with the electrode distribution. Then, the peaks can be utilized as a robust and sensitive indicator for detecting blockage and leakage, as the number of obvious peaks of the open-circuit voltage is directly related to the blockage and leakage location. The blockage and leakage in a fluid tube were successfully detected using the BM-TES with an accuracy of 10 cm. In addition, the BE-TES was able to detect the water flow velocity in the pipe. The experimental results showed that BM-TES can provide a new strategy and method for liquid tube monitoring and has great potential application value in related fields.

The rapid development of flexible triboelectric nanogenerators (TENGs) has become an alternative to batteries for wearable devices. Stretchable, multifunctional, and low-cost are the primary development directions for these wearable devices based on TENG. Herein, a stretchable triboelectric generator with coplanar integration was designed for energy harvesting and force sensing. The industrial conductive silicone and silicone were used to fabricate the TENG with a thickness of less than 0.9 mm. When the elongation was less than 150%, TENG exhibited excellent linear characteristics in the resistance-tensile strain correspondence, and the coefficient of determination was 0.99. This stretchable TENG with a sufficient contact area of 9 cm2 could generate a short-circuit current of 2 µA when it was in contact with the skin. Lastly, an intelligent tension monitoring wearable device that can effectively measure the tensile force was developed. Such a stretchable, coplanar integration-based, and low-cost wearable device has excellent applicability in wearable electronics.

Water-solid triboelectric nanogenerators (TENGs), as new energy collection devices, have attracted increasing attention in ocean energy harvesting and self-powered sensing. Polyacrylic acid (PAA) coating, usually used on the surface of marine equipment, has the property of anti-aging and anti-wear but limits triboelectrical output when used with TENGs. In this paper, polyacrylic acid coating was modified with fluorinated polyacrylate resin (F-PAA) to increase its triboelectrical output, by 6 times, and also to increase its anti-corrosion property. In addition, the corrosion resistance property can be further enhanced by cathodic protection using the electrical output generated by the water-flow triboelectrical energy transfer process. Given their easy fabrication, water-flow energy harvesting, and corrosion resistance, PAA/F-PAA coating-based TENGs have promising applications in river and ocean energy collection and corrosion protection.

Recycling of random mechanical energy in the environment has attracted great research interest in recent years. Herein, we report a rotating triboelectric nanogenerator (rTENG) based on GO@PVDF composite film. Benefit from the effective accumulation of electrostatic charges on the PVDF layers, the as-prepared rTENG shows high output performance. Its peak open-circuit voltage ( V o c ) and short-circuit current ( I s c ) are 35 V and 7.5 μ A, respectively, which are 3 and 3.5 times than pure PVDF based rTENG at 600 rpm, and the maximum power density calculated is 15.2 mW/m−2. Based on the as-prepared GO@PVDF-based rTENG, some practical applications are established, for example, lighting 12 led light bulbs to full brightness and sensing wind speed, which demonstrates the high feasibility and efficiency of the rTENG and manifests that the rTENG could be used in reusing random energy.

Sunflower seed is a popular food, but plenty of bio-waste sunflower husks are discharged into the world. If this bio-waste trash can be recycled, it will be reduced not only environmental pollution but also the waste of resources. In this paper, a triboelectric nanogenerator (SFP-TENG) based on a bio-waste sunflower husk powder is proposed and its open-circuit voltage, short circuit current, and instantaneous power are archived as 488 V, 28. 5 μ A , and 1200 μ W , respectively, under the frequency of 10 Hz with the excitation force of 58 N. The proposed SFP-TENG can harvest the biomechanical energy from the human body’s daily motions. The fabricated SFP-TENG device is capable of lighting up 153 commercial LEDs. Furthermore, the SFP-TENG device is also tested under various humid environments such as 38, 49, 60, 79, and 89% relative humidity. Additionally, it can power up microelectronic devices such as calculator and stopwatch. Hence, we are sure that the proposed device can promote cost-effective and eco-friendly green energy harvesting through recycling bio-wastes as sunflower husk.

Unsuccessful prediction of particle tribocharging in tribocharger is partly due to the complexity of tribocharging process. In this work, computational fluid dynamics-discrete element method (CFD-DEM) modeling approach has been used to investigate particle charge in a cyclone tribocharger. Then particle image velocimetry (PIV) method is used to calculate the particle charge-to-mass ratio. The CaCO3 particle charge in a cyclone tribocharger is simulated and predicted under different gas velocities, particle sizes and moving distances. The simulation results carry out the quantitative and qualitative relationship between different parameters. At the same time, the charge-to-mass ratio between the particle simulation and the experimental results under different gas velocities is compared, and the results are all in the magnitude of 10−4. Experimental results in terms of particle charge-to-mass ratio are thus obtained. The CFD-DEM model is verified by comparison with the experimental results

Scalable preparation of flexible, porous, and microstructure membrane for triboelectric nanogenerators (TENGs) with controllable thickness and high contact surface area using cost-effective methods is still a great challenge. Herein, we developed a novel, cost-effective, and scalable fabrication procedure for the preparation of a lightweight, flexible, thin, and porous polyurethane (PU) membrane for a TENG device. Importantly, the thickness and pore size of the PU membrane can be tuned easily. The PU-based TENG device fabricated with a porous PU membrane of 5 μm thickness and 15 μm pore size (PU-5-15) generated a maximum peak to peak output voltage was 58.5 V with a corresponding peak to peak current was 1.37 μA at 4 N and power density of 9.7 mW/m2. The device was systematically used to energize 24 green commercial lightemitting diodes (LEDs) in brighter condition connected in series and to turn on the LCD of a portable timer clock within 51 s and glow for 1 s after 187 taps. The developed TENG device also exhibited stable cyclic charging and discharging property that is very important for real applications. Furthermore, the energy-harvesting performance of the device was also tested with human body movements. The developed industrially compatible method is very easy and convenient, and mass production is possible. Compared to other studies, in this novel study, we achieved a higher electrical performance at the desired lower thickness for the porous PU membrane-based TENG device. The developed fabrication method will pave the way for the facile and scalable industrial processing of PU membranes for energy-harvesting applications.

A patterned transparent electrode is a crucial component of state-of-the-art wearable devices and optoelectronic devices. However, most of the patterning methods using silver nanowires (AgNWs), which is one of the outstanding candidate materials for the transparent electrode, wasted a large amount of unused AgNWs during the patterning process. Here, we report a highly efficient patterning of AgNWs using electrospray deposition with grounded electrolyte solution (EDGE). During electrospray deposition, a patterned electrolyte solution collector attracted AgNWs by strong electrostatic attraction and selectively deposited them only on the patterned collector, minimizing AgNW deposited elsewhere. The enhanced patterning efficiency was verified through a comparison between the EDGE and conventional process by numerical simulation and experimental validation. As a result, despite the same electrospray deposition conditions for both cases except for the existence of the electrolyte solution collector, the coverage ratio of AgNWs fabricated by the EDGE process was at least six times higher than that of AgNWs produced by the conventional process. Furthermore, the EDGE process provided high design flexibility in terms of not only the material of the substrate, including a polymer and a ceramic but also the shape of the substrate, including a 2D flat and 3D curved surface. As an application of the EDGE process, a self-powered touch sensor exploiting the triboelectric effect was demonstrated. Thus, the EDGE process would be utilized in further application in wearable or implantable devices in the field of biomedicine, intelligent robots, and human–machine interface.

Due to their simple structure, low cost, and self-powered characteristics, triboelectric nanogenerators are widely used in mechanical sensing fields. However, the existing investigations on triboel...

Droplet motion state monitoring is important in microfluidic applications, such as biomedicine, drug delivery, and metal ion extraction. Here, a nonintrusion monitoring method of droplet motion state via liquid-solid contact electrification is proposed, and a triboelectric droplet motion state sensor (TDMSS) is fabricated. Droplet counting and droplet size monitoring can be realized by signal processing and information extracting of the voltage pulse. The experimental results show that the number of droplets increases linearly with the increase of liquid flow, and the linearity is 0.9854. Moreover, TDMSS can stably monitor the number of droplets in different motion states. In addition, the output pulse width is sensitive to droplet size, and the droplet length ranges from 3 to 13.5 mm. More importantly, TDMSS can realize the function of droplet counting and size monitoring of a conductive liquid and accurate droplet counting under different inclination angles and motion states. This work not only provides a nonintrusion method for droplet motion state monitoring but also makes a solid step for microfluidic sensing technology based on a triboelectric nanogenerator.

Triboelectric nanogenerators (TENGs) are useful for harvesting clean and widely distributed water droplet energy with high efficiency. However, the commonly used polymer films in TENGs for water droplet energy harvesting have the disadvantages of poor breathability, poor skin affinity, and irreparable hydrophobicity, which greatly hinder their wearable uses. Here, we report an all-fabric TENG (F-TENG), which not only has good air permeability and hydrophobic self-repairing properties but also shows effective energy conversion efficiency. The hydrophobic surface composed of SiO2 nanoparticles and poly(vinylidenefluoride-co-hexafluoropropylene)/perfluorodecyltrichlorosilane (PVDF-HFP/FDTS) exhibits a static contact angle of 157° and displays excellent acid and alkali resistance. Because of its low glass transition temperature, PVDF-HFP can facilitate the movement of FDTS molecules to the surface layer under heating conditions, realizing hydrophobic self-repairing performance. Furthermore, with the optimized compositions and structure, the water droplet F-TENG shows 7-fold enhancement of output voltage compared with the conventional single-electrode mode TENG, and a total energy conversion efficiency of 2.9% is achieved. Therefore, the proposed F-TENG can be used in multifunctional wearable devices for raindrop energy harvesting.

Biopolymers have attracted considerable attention in various biomedical applications. Among them, cellulose as sustainable and renewable biomass has shown potential efficacy. With the advancement in nanotechnology, a wide range of nanostructured materials have surfaced with the potential to offer substantial biomedical applications. . The progress of cellulose at the nanoscale regime (nanocelluloses) with diverse forms like cellulose nanocrystals, nanofibres and bacterial nanocellulose) has imparted remarkable properties like high aspect-ratio and high mechanical strength, and biocompatibility. The amalgamation of nanocellulose together with magnetic nanoparticles (MNC) could be explored for a synergistic effect. In this review, a brief introduction of nano cellulose , magnetic nanoparticles and the synergistic effect of MNC is described. Further, the review sheds light on the recent studies based on MNCs with their potential in the biomedical area. Finally, the review is concluded by citing the remarkable value of MNC with their futuristic applications in other fields like friction layers for triboelectric nanogenerator (TENG), energy production, hydrogen splitting, and wearable electronics.

There has been a significant increase in the number of total knee replacement (TKR) surgeries over the past few years, particularly among active young and elderly people suffering from knee pain. Continuous and optimal monitoring of the load on the knee is highly desirable for designing more reliable knee implants. This paper focuses on designing a smart knee implant consisting of a triboelectric energy harvester and a frontend electronic system to process the harvested signal for monitoring the knee load. The harvester produces an AC signal with peak voltages ranging from 10 V to 150 V at different values of knee cyclic loads. This paper demonstrates the measurement results of a PCB prototype of the frontend electronic system fabricated to verify the functionality and feasibility of the proposed approach for a small range of cycling load. The frontend electronic system consists of a voltage processing unit to attenuate high peak voltages, a rectifier and a regulator to convert the input AC signal into a stabilized DC signal. The DC voltage signal provides biasing for the delta-sigma analog-to-digital converter (ADC). Thus, the output of the triboelectric harvester acts as both the power signal that is rectified/regulated and data signal that is digitized. The power consumption of the proposed PCB design is approximately $5.35~\mu \text{W}$ . Next, the frontend sensor circuitry is improved to accommodate a wider range of cyclic load. These results demonstrate that triboelectric energy harvesting is a promising technique for self-monitoring the load inside knee implants.

Gesture recognition is one of the most important functions of human-computer interaction (HCI). In this regard, a self-powered finger ring hand motion sensor was proposed in the present study. To this end, a single sensing unit consisting of a Polydimethylsiloxane (PDMS) film, a polyethylene oxide (PEO) film and a spacer was constructed. Then the finger bending and stress were monitored through numerous sensing units. In order to increase the contact area, ordinary textile stripes were used on the PDMS film surface. Then finite element simulations were carried out to evaluate the performance of the proposed sensor under different conditions. The obtained results show that the sensor has promising charge transfer features. Moreover, it was found that the sensitivity of the sensing unit in the range of 0–7 N is 94.48 mV/N. Then the ring finger hand motion sensor was set on a single finger to simulate a mouse and distinguish click, double-click and click time. Accordingly, it was demonstrated that numbers, letters and phrases in the ASL sign language can be accurately identified even in similar cases with small differences.

In recent years, triboelectric nanogenerators (TENGs) have developed rapidly and attracted the attention of researchers all over the world. Here, a novel waved-shaped triboelectric nanogenerator using the MgSiO3 powder (W-TENG) was developed. In this work, polyethylene terephthalate film and MgSiO3 powder form the triboelectric pairs. W-TENG devices can convert mechanical energy into electric energy. From the results, the maximum output power of a W-TENG can reach 184 µW. Additionally, a W-TENG can generate an open-circuit voltage (Voc) of 224.26 V, a short-circuit current (Isc) of 2.74 µA, and a transferred charge of 37.8 nC. Moreover, a W-TENG can serve as a self-powered human motion counter. This design describes a portable TENG device that can promote the self-powered human motion sensor application.

The demand for flexible, efficient, and self-powered cochlear implants applied to remedy sensorineural hearing loss caused by dysfunctional hair cells remains urgent. Herein, we report an acoustic core-shell resonance harvester for the application of artificial cochleae based on the piezo-triboelectric effect. Integrating dispersed BaTiOsub3/subparticles as cores and porous PVDF-TrFE as shells, the acoustic harvest devices with ingenious core-shell structures exhibit outstanding piezo-triboelectric properties (iV/isubioc/i/sub= 15.24 V,iDA/isubisc/i/sub= 9.22 mA/msup2/sup). The acoustic harvest principle reveals that BaTiOsub3/subnanocores resonate with sound waves and bounce against porous PVDF-TrFE microshells, thereby generating piezo-triboelectric signals. By experimental measurement and numerical modeling, the vibration process and resonance regulation of acoustic harvest devices were intensively investigated to regulate the influential parameters. Furthermore, the acoustic harvesters exhibit admirable feasibility and sensitivity for sound recording and show potential application for artificial cochlea.

Highlights •Mechanical stimuli-triggered optical responses of cholesteric liquid crystal devices are realized.•Self-powered bistable smart window and E-paper are demonstrated.•Self-powered optical switch is developed for remote control.Intelligent responsive devices are crucial for a variety of applications ranging from smart electronics to robotics. Electro-responsive cholesteric liquid crystals (CLC) have been widely applied in display panels, smart windows, and so on. In this work, we realize the mechanical stimuli-triggered optical responses of the CLC by integrating it with a triboelectric nanogenerator (TENG), which converts the mechanical motion into alternating current electricity and then tunes the different optical responses of the CLC. When the voltage applied on the CLC is relatively low (15–40 V), the TENG drives the switching between the bistable planar state and focal conic state of the CLC, which shows potential applications in self-powered smart windows or E-paper displays. When the voltage supplied by the TENG is larger than 60 V, a self-powered optical switch is demonstrated by utilizing the transformation between focal conic state and instantons homeotropic state of the CLC. This triboelectric-optical responsive device consumes no extra electric power and suggests a great potential for future smart electronics.

Lack of low-cost, large area deposition methods and photo-patternability of high-performance piezoelectric materials restrict the rapid development of efficient functional devices like sensors and energy harvesters. In this paper, we report an optimized process flow for Zinc Oxide (ZnO)/SU-8 and Barium Titanate (BTO)/SU-8 based nanocomposite thin films for mechanical energy harvesting (MEH) applications. Parametric variation of process variables for these nanocomposites reveals that 15% ZnO/SU-8 and 20% BTO/SU-8 nanocomposites show optimum results with good piezoelectric response and UV transmittance, allowing reliable lithography of the nanocomposites. Furthermore, three different types of energy harvesting devices are fabricated using these nanocomposites as piezoelectric layer. Output powers of $223~\mu \text{W}$ (ZnO/SU-8) and $642~\mu \text{W}$ (BTO/SU-8) are produced at resonance for the conventional cantilever type MEH devices at an input acceleration of 0.5g. Using the nanocomposites as flexible nanogenerator, open circuit voltages of 570 mV (ZnO/SU-8) and 780mV (BTO/SU-8) are obtained using regular finger pressing. The hybrid energy harvesters, based on combined piezoelectric-triboelectric transduction mechanisms, generate output voltages of 0.4V, 0.95V, 1.4V (ZnO/SU-8) and 0.7V, 1.1V and 1.9V (BTO/SU-8) in piezoelectric, triboelectric and hybrid operations, respectively.

In this work, synergistic effects derived from surface engineering and dielectric property tuning were exploited to enhance the output performance of a triboelectric nanogenerator (TENG) based on an inorganic/porous PDMS composite in a contact-separation mode. BaTiO3 (BT)/porous PDMS films with different BT weight ratios were fabricated and evaluated for triboelectric nanogenerator (TENG) application. Maximum output signals of ca. 2500 V, 150 μA, and a power density of 1.2 W m-2 are achieved from the TENG containing 7 wt % BT, which is the best compromise in terms of surface roughness, dielectric constant, and surface contact area as evidenced by SEM and AFM studies. These electrical signals are 2 times higher than those observed for the TENG without BT. The 7BT/porous PDMS-based TENG also shows high stability without a significant loss of output voltage for at least 24 000 cycles. With this optimized TENG, more than 350 LEDs are lit up and a wireless transmitter is operated within 9 s. This work not only shows the promoting effects from porous surfaces and an optimized dielectric constant but also offers a rapid and template/waste-free fabrication process for porous PDMS composite films toward large-scale production.

Knitted textiles as one kind of outstanding flexible substrate that have been universally applied in smart wearables. Structural design and output performance analysis of knitted-based triboelectric nanogenerators (TENGs) is significant research points. It is essential to provide inspiration in the TENGs applications. In this study, we designed and fabricated a fish-scale-based triboelectric nanogenerator using a formed knitted textile composed of commercial threads as a pair of contact areas. The deformation of the scale-shaped fabric was from the three-dimensional structure, which provided an effective contact area. We investigated the elastic yarn specification and scale-shaped distribution and analyzed their output performance in the frequency domain using fast Fourier transform. The result illustrated that the amplitude, phase, and power spectrum had obvious differences and can reflect the working states during the motions. The power spectrum could reach the maximum value of 280, which showed the potential for applications in the low-frequency motion.

Using triboelectric nanogenerators (TENGs) to harvest blue energy in the ocean is advanced technology at present. In wave environments, the wave magnitude is constantly changing, so designing a TENG that can adjust the energy harvesting ability is necessary. Herein, a graded energy harvesting triboelectric nanogenerator (GEH-TENG) is fabricated, in which double generation units can operate in different transmission states to adapt to wave changes. Under small waves, the GEH-TENG is in the primary transmission state. Once waves are large enough, it enters the secondary transmission state, realizing graded energy harvesting to enhance power generation performance. Experiments show that when the input frequency is 1.0 Hz and the amplitude is 120 mm, the GEH-TENG can generate 0.7 mJ of energy in a single operation cycle, which is 2.3 times of it without grading. Moreover, it can be placed on the shore to monitor ocean wave conditions. An idea of graded energy harvesting is proposed in this study, and the proposal provides useful guidance for practical applications of TENGs in ocean wave condition monitoring.

Triboelectric nanogenerator (TENG) is the new technique that can convert low-frequency mechanical energy into effective electricity. As an energy collector, the pursuit of high output characteristics is understandable. Although high charge density has been achieved by working in high vacuum or charge pumping techniques, it remains challenging to obtain the high output performance directly in the atmosphere. Herein, surface-engineering of the triboelectric layer for enhancing output performance has been reviewed carefully. By constructing surface morphology or developing surface modification, high performance of TENGs is finally presented in the review.

Wearable or portable electronic devices are ubiquitous because those enrich our life considering comfortability, efficiency and healthcare. However, those devices are nothing but accessories without electric power. Exchanging or recharging batteries are not always reachable for the devices. Energy harvesting systems which harvest energy from human motions are a good alternative or assist for batteries to secure electric power. Among other energy harvesters, a triboelectric generator (TEG) has attracted much interest with respect to its simplicity and lightweight. Many works have been done to enhance performance of TEGs to apply them for practical uses. Among them, introduction of structures on surface is a rational approach because triboelectricity is a contact electrification. In this review, works of enhancement of TEG’s output performance are highlighted with respect to structural modification on the surface of triboelectric films. Molding or imprinting straightforwardly introduces micro-, nano-, or hierarchical structures on triboelectric surfaces and the TEG with a film of pyramidal structures exhibited up to 800% increase in the output compared with flat ones. Porous structures with pores on and inside polymeric films also showed up to 800% increase in the output. And TEGs based on nano-fibers with hierarchical structures on them showed up to around 2000% improvement in electrical outputs.

The marine internet of things (MIoT), an increasingly important foundation for ocean development and protection, consists of a variety of marine distributed sensors under water. These sensors of the MIoT have always been highly dependent on batteries. To realize in situ power supply, a flexible seaweed-like triboelectric nanogenerator (S-TENG) capable of harvesting wave energy is proposed in this study. The flexible structure, designed with inspiration from the seaweed structure, processes extensive marine application scenarios. The bending and recovering of the S-TENG structure under wave excitations are converted to electricity. As the output performance increases with the number of parallel connected S-TENG units, an S-TENG system with multiple units could serve for floating buoys, coastal power stations, and even submerged devices. Through the demonstration experiments performed in this study, the flexible, low-cost S-TENG could become an effective approach to achieve a battery independent MIoT.

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 (

The triboelectric nanogenerator (TENG) has the advantages of low cost, high efficiency, flexibility, lightness, and portability. Therefore, it has caused more and more attention as an electronic skin sensor. Generally, the research on intelligent components mainly focused on flexible pressure or temperature sensors. However, the surface roughness recognition of object material still remains a challenge. Meanwhile, most of the current surface roughness recognition methods need secondary processing of the sensor signal, and rarely use the signal generated by the sensor to directly identify the surface roughness. In this paper, the load-dependent electric field model is transplanted to the conductor-dielectric contact-separation TENG (CS-TENG), and the surface roughness of conductor can be differentiated theoretically based on the output of CS-TENG. To verify its effectiveness, the TENG devices were fabricated and the home-processed steels of different roughness act as the conductor layers. By contacting the conductor layer with the dielectric layer, the electric output signal based on contact induced electrification can be generated, which can be used to quantitatively estimate the surface roughness of steels. The test results demonstrate that the output of CS-TENG decreases with the increase of surface roughness, which coincides with the simulation prediction. This method is low cost and easy to implement, which provides a new design idea to extend the functions of TENGs as tactile electronic skins.

Triboelectric separation is an efficiency and promising method to recycle waste plastics. Fluidized bed has been proved an optimal tribocharger with excellent bipolar charging performance for binary granules. In this work, the tribo-charging characteristics of PE, PP, PET and PVC granules during fluidization were investigated using a bench-scale fluidized bed. The results showed that the triboelectric series obtained by fluidization charging was: (−)-PVC–PET–PP–PE-(+). The study of fluidization tribo-charge rate of plastics showed that the fluidization charge rate of five binary granule combinations was PE–PVC > PP–PVC > PE–PET > PP–PET > PET–PVC. And the saturated charge-to-mass ratio of five combinations shared the same trend with the tribo-charging rate. In addition, the tribo-charging and the separation characteristics of the ternary granules, namely PP, PET, and PVC were analyzed, and the results showed that PP plastics were mainly distributed near the negative plate, while PET and PVC were close to the positive one.

Recent advances have led to the development of intelligent drug-delivery systems such as microchips, micropumps, and soft devices with sensors; however, the facile preparation of transdermal and implantable systems modulable to various stimuli remains elusive. In addition, the use of a battery limits their wearable and implantable applications. Therefore, to overcome these disadvantages, we herein suggest a facile strategy to prepare electro-mechanochemically responsive soft gel composites with molecular gatekeeper-based nanocontainers. We found that a metal-phenolic coordination network can act as an efficient self-healable and adaptive gatekeeper in response to electrical and mechanical stimuli owing to the reversible dynamic bonds and adhesiveness to the silica surface. The porous channels of mesoporous silica nanoparticles are filled with guest molecules, and the exterior is wrapped with metal-tannic acid (TA) networks. Owing to the robustness of metal-phenolic network, the guest molecules are efficiently entrapped in the channels but released by electrical and ultrasound input. Voltage-dependent changes in the guest release rate provide control over the dosage on demand. The combination of hydrogel matrixes with the responsive nanocapsules enables the construction of a series of adaptive gel composites capable of successive guest release in response to electrical, ultrasound, electromechanical, and triboelectric stimuli. The Korsmeyer-Peppas model revealed that the release mechanism is non-Fickian, which indicates the presence of boundaries around the guest-loading channels (n = 0.739, R2 = 0.9574 when 2 V is applied). This study realized efficient platforms for active-type drug-delivery applications based on transdermal patches and implantable gels with remotely controllable release characteristics.

A flexible and stable power supply is essential to the rapid development of wearable electronic devices. In this work, a transparent, flexible, temperature-stable and ionogel electrode-based self-healing triboelectric nanogenerator (IS-TENG) was developed. The ionogel with excellent stretchability (1,012%), high ionic conductivity (0.3 S·m−1) and high-temperature stability (temperature range of −77 to 250 °C) was used as the electrode of the IS-TENG. The IS-TENG exhibited excellent transparency (92.1%) and stability. The output performance did not decrease when placed in a 60 °C oven for 48 h. In addition, the IS-TENG behaved like a stable output in the range of −20 to 60 °C. More importantly, the IS-TENG could also achieve self-healing of electrical performance at temperatures between −20 and 60 °C and its output can be restored to its original state after healing. When the single-electrode IS-TENG with an area of 3 cm × 3 cm was conducted under the working frequency of 1.5 Hz, the output values for open-circuit voltage, short-circuit current, short-circuit transferred charge, and maximum peak power density were 189 V, 6.2 µA, 57 nC, and 2.17 W·m−2, respectively. The IS-TENG enables to harvest biomechanical energy, and drive electronic devices. Furthermore, the application of IS-TENGs as self-driven sensors for detecting human behavior was also demonstrated, showing good application prospects in the field of wearable power technology and self-driven sensing.

Triboelectrification and its underlying mechanisms have been studied over several decades to provide us with deterministic tools which can predict the occurrence of such phenomenon. This has also produced many charge transfer models that have been validated by some experiments and contradicted by others. However, certain trends have emerged which provide insight for a general charge evolution model. Variations produced by impact conditions and solids surface properties have been discussed in greater detail in recent years and their effects need to be modeled as well. Of particular interest is the occurrence of bipolar charging in insulative particle systems. While models can predict such behavior with suitable work function differences, justifying this for particles of the same material is not obvious. Aside from discrete models, simulation setup and parameters used have also significant impact on outcomes. These factors and their implications are reviewed in this paper while highlighting shortcomings that need to be addressed.

Flexible triboelectric nanogenerators (TENGs) have attracted much attention because of its environmentally friendly, practical, and cost-producing advantages. In flexible TENGs, it is important to study the flexible electrodes in order to fabricate the fully flexible devices. Here, we compared electrical characteristics of the sponge porous polydimethylsiloxane (PDMS)-based flexible TENGs with two types of flexible electrodes, copper and carbon nanotube (CNT)-PDMS electrodes. The output voltage and maximum power density of sponge PDMS-based flexible TENGs with copper and CNTPDMS electrodes were compared. The voltage and power density of sponge PDMS-based flexible TENGs with CNT-PDMS electrodes were improved compare to those with copper electrodes. The output voltage and the maximum power density of sponge PDMS-based flexible TENGs with copper and CNT-PDMS electrodes increased 4 times and 7 times, respectively. It is attributed to higher electrical conductivity and stably flow electricity of CNT than those of copper.

A noise detection system (INDS) composed of an acoustic triboelectric nano-generator (TENG) and an electrical bilayer synaptic transistor (EDLT) is proposed. As a self-powered sound sensor, TENG converts the sound signal directly into a voltage signal output. EDLT is used as a neuromorphic device to simulate synaptic behavior in organisms and has the ability to store and process signals simultaneously. In this letter, a kind of intelligent, simple structure and humanized noise detection system is developed.

We report an intriguing triboelectrification behavior of thermally treated P(VDF-TrFE) polymers. Cooled (C-) and annealed (A-) P(VDF-TrFE) films were prepared by the rapid cooling of the melt solution and the subsequent annealing, respectively. The C–P(VDF-TrFE) had sparse grains and small elastic modulus and surface charge density, while, the A-P(VDF-TrFE) had dense grains and large elastic modulus and surface charge density. When the polymers contacted ITO electrodes, the triboelectric outputs of C-(PVDF-TrFE) were larger than those of A-P(VDF-TrFE). When the polymers contacted each other, the triboelectric outputs of different P(VDF-TrFE) films were significantly larger than those of similar P(VDF-TrFE) films. Based on detailed X-ray photoemission spectroscopy results, we suggested that roughness-induced frictional heat and elastic modulus differences may play an important role in minute material and/or ion transfer during the triboelectrification of identical P(VDF-TrFE) polymers.

Wood is a state-of-art, renewable, and sustainable building material with excellent mechanical properties but negligible triboelectric polarizability. Strategies to improve and rationally tune the triboelectric properties of wood are needed to further its application for mechanical energy harvesting in smart buildings. We found that wood becomes more triboelectrically positive when modified by in situ-grown zeolitic imidazolate framework-8 (ZIF-8), a metal-organic framework (MOF), and more triboelectrically negative when coated with poly(dimethylsiloxane) (PDMS). A triboelectric nanogenerator (TENG) made with two radial-cut wood samples (L x R x T: 35 x 20 x 1 mm(3)), respectively functionalized with ZIF-8 and PDMS, can generate an open-circuit voltage (Voc) of 24.3 V and a short-circuit current (Isc) of 0.32 mu A upon 50 N, 80 times higher compared with that of native wood. We demonstrate the applicability of our functionalized wood TENG (FW-TENG) in smart buildings by using it to power household lamps, calculators, and electrochromic windows. ISSN:2590-2385

In response to the testing requirements of downhole positive displacement motor (PDM), this research proposes a self-powered multifunctional sensor based on the triboelectric nanogenerator that can simultaneously measure the rotating speed, rotating angle and abrasion. Tests, including speed measurement tests, angle measurement tests, abrasion tests and reliability tests, were respectively tested after the sensor is manufactured. Speed tests results show that the measurement range is 0 to 900 r/min, the measurement error is less than 3%, and the maximum output voltage amplitude can reach 5.5 V. Angle tests results show that the minimum resolution is 60 degrees, and the measurement error is less than 5%. Abrasion tests results show that three abrasion thresholds of 0 mm, 0 to 20 mm and greater than 20 mm can be detected. Reliability tests results show that the sensor can work normally in an environment where the temperature is less than 250 degrees Celsius and the humidity is less than 90%. In addition, the power generation performance had also been tested, and the results show that the friction model and the sensing model of the sensor can output a maximum power of $28.3 \times 10.9\text{W}$ and $5.7 \times 10.9\text{W}$ respectively when connected in series with a 1000M $\Omega $ load. Compared with the traditional downhole sensors, this research can working normally in self-powered model at higher temperatures, and has more measurement parameters.

Triboelectric nanogenerators (TENGs) can convert human biomechanical activities into electricity. They have been used in many biomedical and healthcare applications due to their attractive features such as the wide range of biocompatible materials, simple fabrication process, portable size, high output power, and low cost. Recently, they have been combined with drug delivery systems as an emerging technology to achieve on-demand and controllable release of drugs. This review comprehensively highlights the current development of TENG-based self-powered drug delivery systems from three different mechanisms, including microfluidics, electrophoresis, and iontophoresis. Although there are still some challenges remaining to be addressed, TENG-based drug delivery systems are promising as a new option for drug administration and could play an important role in personalized healthcare.

Self-powered sensors based on triboelectric nanogenerators (TENGs) are increasingly used in real-life applications, especially for monitoring water pollution, rain pH, and the like. Here, we fabric...

Converting various types of ambient mechanical energy into electricity, triboelectric nanogenerator (TENG) has attracted worldwide attention. Despite its ability to reach high open-circuit voltage up to thousands of volts, the power output of TENG is usually meager due to the high output impedance and low charge transfer. Here, leveraging the opposite-charge-enhancement effect and the transistor-like device design, we circumvent these limitations and develop a TENG that is capable of delivering instantaneous power density over 10 MW/m2 at a low frequency of ~ 1 Hz, far beyond that of the previous reports. With such high-power output, 180 W commercial lamps can be lighted by a TENG device. A vehicle bulb containing LEDs rated 30 W is also wirelessly powered and able to illuminate objects further than 0.9 meters away. Our results not only set a record of the high-power output of TENG but also pave the avenues for using TENG to power the broad practical electrical appliances., TENG suffers from two fundamental limitations: high output impedance and low charge transfer. Herein, these limitations are circumvented by leveraging the opposite-charge-enhancement effect and transistor-like device design, thereby achieving the instantaneous power density over 10 MW/m2 at the low frequency of ~ 1 Hz.