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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.

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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.

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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 Cr3+ -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.

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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 cm2 contact area at an external load of 106 Ω, respectively. Strikingly, excellent stability and durability are demonstrated after continuous cycles up to 104 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.

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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.

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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.

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Triboelectric nanogenerators are remarkable devices that show great potential in harvesting energy from mechanical work and are generally used for sensing purposes. Here we report a novel method for the fabrication of ZnO microspheres and the formation of TENG based on ZnO/PDMS composite. The zinc oxide microspheres with needle decorated structure via thermal oxidation of metallic zinc was grown at 500 °C. The TENG was then fabricated using ZnO/PDMS composite with Au sputtered electrode. While PDMS is a good triboelectric material, its output power density is low. Embedding ZnO micro/nanostructures in PDMS increases the output power of PDMS-based TENG manifolds. ZnO with a high dielectric constant exhibits semiconductor properties as well as piezoelectric properties. This combines with the triboelectric properties of PDMS and gives a significant boost to the TENG performance. This composite structure is used for the fabrication of high output power density TENG using contact separation mode, where the power density of 27Wm-2was achieved. Consequently, a novel device application to detect surface charge density through the fabricated TENG is reported and the subsequent reconstruction of surface charge topology based on the detected surface charge density on large surfaces is presented. This technique may be used for the study of surface charge morphology, electrostatics, triboelectric constants, and various other material properties for characterization and application purposes.

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The underwater ultrasound power measurement has become necessary due to the rapid development of sonochemistry and sonocatalysis. This article presents construction of novel triboelectric nanogenerator (TENG) and its application for a detection of ultrasonic waves in water. The device was 3D printed using widely available and cost-effective materials. TENG consisted of the device housing and movable polymer pellets confined between flat electrodes. The device housing and pellets were 3D printed via stereolithography (SLA) and fused deposition modelling (FDM) methods, respectively. The pellets moved periodically driven by the ultrasonic waves leading to generation of an alternating voltage signal. The electric response of TENG was calibrated using a commercially available ultrasonic power sensor. The open-circuit voltage output of TENG was registered in different sections of the ultrasonic bath in order to determine the distribution of the acoustic power. TENG electric responses were analyzed by applying the fast Fourier transform (FFT) and fitting the theoretical dependence to experimental data. The main peaks in the frequency spectra of the voltage waveforms corresponded to the fundamental excitation frequency of the ultrasonic bath. TENG device, presented in this paper, can be successfully applied as a self-powered sensor for detection of ultrasonic waves. It enables precise control of the sonochemical process and reduction of power losses of the ultrasonic reactor. 3D printing technology has been confirmed to be fast, easy, and scalable method of fabrication of the ultrasonic sensors.

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This paper suggests a straightforward and rapid fabrication method applying the integration of 3D printing and triboelectric nanogenerator (TENG) technologies to realize milli/microfluidic multipurpose devices. The proposed liquid-solid TENG device is served as an energy harvester and sensor at the same time with flexibility in operation modes. Accordingly, an innovative ethylene vinyl acetate (EVA)-made millifluidic pH sensor is fabricated based on zinc oxide nanosheets as a showcase of the functional adaptability of the ubiquitous device, and its performance is analyzed and compared with contemporary electrochemical pH sensors. High crystallinity of the nanosheets with an incline to (103) orientation in parallel with high levels of oxygen vacancies provides capacity for surface charge accumulation at the nanosheet-aqueous solution interface and the ensuing ultrahigh sensitivity of the triboelectric sensor. The millichannel is optimized in terms of sensing surface area, flow rate, and hydrophobicity properties by opting for appropriate geometry, TENG operation modes, and materials. Despite the finding that quasi-single-electrode mode TENG experiences a higher response (8.12 × Nernst limit) in comparison with quasi-contact-separation configuration (4.14 × Nernst limit), the latter enjoys superior linearity, stability, repeatability, reproducibility, and reliability characteristics corresponding to R2 of 98.93%, drift rate of 13 mV/h, relative standard deviation (RSD) of 1.23% in third hysteresis loop, 2.24%, and maximum standard error of ±0.2 pH units across multiple trials, respectively, in a wide pH range of 2-13. Time- and cost-effectiveness, user-friendliness, self-powering, portability, and biocompatibility of the device could be asserted as considerable advantages to open the door for feasibly realizing the new generation of real-life and point-of-care devices.

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The triboelectric series is a generally accepted method for describing the triboelectric effect. It provides a way to control the double face of the ubiquitous triboelectric effect: causes of unpredictable accidents and the resultant surface charge as energy sources. However, previous studies have been biased in solids despite being observed in liquids (liquid-solid contact electrification). Therefore, a liquid triboelectric series is necessary to be established to manipulate the liquid triboelectric effect according to the appropriate goal. In this study, a liquid triboelectric series is first established to describe the triboelectric properties of each liquid when contact electrification occurs with a solid surface. The liquid triboelectric series covers electrolytes, organic solvents, oxidants, and higher sugar alcohols. Common chemical groups can be derived from the liquid triboelectric series that hydroxyl groups enhance, and benzene groups suppress the liquid triboelectric effect. The results are demonstrated by the amplified efficiency of an energy harvester and particle contamination after surface washing. This study will play a pivotal role in understanding the liquid-solid contact electrification phenomenon and providing new perspectives on the applications of the liquid triboelectric effect.

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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.

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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.

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The massive production of polymer-based respiratory masks during the COVID-19 pandemic has rekindled the issue of environmental pollution from nonrecyclable plastic waste. To mitigate this problem, conventional filters should be redesigned with improved filtration performance over the entire operational life while also being naturally degradable at the end. Herein, we developed a functional and biodegradable polymeric filter membrane consisting of a polybutylene adipate terephthalate (PBAT) matrix blended with cetyltrimethylammonium bromide (CTAB) and montmorillonite (MMT) clay, whose surface properties have been modified through cation exchange reactions for good miscibility with PBAT in an organic solvent. Particularly, the spontaneous evolution of a partial core-shell structure (i.e., PBAT core encased by CTAB-MMT shell) during the electrospinning process amplified the triboelectric effect as well as the antibacterial/antiviral activity that was not observed in naive PBAT. Unlike the conventional face mask filter that relies on the electrostatic adsorption mechanism, which deteriorates over time and/or due to external environmental factors, the PBAT@CTAB-MMT nanofiber membrane (NFM)-based filter continuously retains electrostatic charges on the surface due to the triboelectric effect of CTAB-MMT. As a result, the PBAT@CTAB-MMT NFM-based filter showed high filtration efficiencies (98.3%, PM0.3) even at a low differential pressure of 40 Pa or less over its lifetime. Altogether, we not only propose an effective and practical solution to improve the performance of filter membranes while minimizing their environmental footprint but also provide valuable insight into the synergetic functionalities of organic-inorganic hybrid materials for applications beyond filter membranes.

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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.

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Control of work function (WF) in graphene is crucial for graphene application in electrode material replacement and electrode surface protection in optoelectronic devices. Although efforts have been made to manipulate the effective WF of graphene to optimize its application, most studies have focused on graphene employed in static electrical contact interfaces. In this work, we investigated WF variations of supported single-layer graphene (SLG) in sliding electrical contact under ambient conditions, which was achieved by sliding an electrically biased conductive atomic force microscopy (cAFM) probe on the SLG surface. The effective WF, structural properties, and chemical compositions of rubbed SLG were subsequently measured by Kelvin probe force microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy, respectively. We found that the effective WF of the rubbed SLG was governed by both the tunneling triboelectric effect (TTE) and tribochemical-induced surface functionalization. The TTE charges generated by the sliding cAFM probe tunneled through the structural defects of the SLG and were trapped underneath the SLG. The SLG will be either p-doped or n-doped depending on the type of TTE charges and the polarity of electric bias applied to the cAFM probe during the rubbing process. However, the applied electric bias also led to the electrolysis of a water meniscus formed at the cAFM probe-SLG contact, resulting in surface oxidation and the increase of SLG WF. Further absorption of ambient water molecules on the oxygenated functional groups gradually reduced the SLG WF. The influence of TTE and surface functionalization on the SLG WF depends on the magnitude and polarity of applied electric biases, relative humidity, and physical properties of the supporting substrates. Our results demonstrate that the effective WF of SLG in a sliding electrical contact interface will vary with time and might need to be considered for related applications.

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Differential diagnosis of pathogenic diseases, presently coronavirus disease 2019 (COVID-19) and influenza, is crucial with due attention to their superspreading events, presumably long incubation period, particular complications, and treatments. In this paper, a label-free, self-powered, and ultrafast immunosensor device working based on triboelectric effect is proposed. Equilibrium constants of specific antibody-antigen reactions are accompanied by IEP-relevant electric charges of antigens to recognize SARS-CoV-2 and H1N1. Simulation attributes including fluid flow and geometrical parameters are optimized so that the maximum capture efficiency of 85.63% is achieved. Accordingly, antibody-antigen complexes form electric double layers (EDLs) across the channel interfaces. The resultant built-in electric field affects the following external electric field derived from triboelectricity, leading to the variation of open-circuit voltage as a sensing metric. The device is flexible to operate in conductor-to-dielectric single-electrode and contact-separation modes simultaneously. While the detection limit is reduced utilizing the single-electrode mode compared to the latter one, surface treatment of the triboelectric pair contributes to the sensitivity enhancement. A threshold value equal to -4.113 V is featured to discriminate these two viruses in a vast detectable region; however, further surface engineering can allow the on-site detection of any electrically-charged pathogen applying the emerging triboelectric immunosensor enjoying a lower detection limit.

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Utilizing the triboelectric effect of the fibrous structure, a very low cost and straightforward sensor or an energy harvester can be obtained. A device of this kind can be flexible and, moreover, it can exhibit a better output performance than a device based on the piezoelectric effect. This study is concerned with comparing the properties of triboelectric devices prepared from polyvinylidene fluoride (PVDF) fibers, polyamide 6 (PA) fibers, and fibrous structures consisting of a combination of these two materials. Four types of fibrous structures were prepared, and then their potential for use in triboelectric devices was tested. Namely, individual fibrous mats of (i) PVDF and (ii) PA fibers, and their combination-(iii) PVDF and PA fibers intertwined together. Finally, the fourth kind was (iv), a stratified three-layer structure, where the middle layer from PVDF and PA intertwined fibers was covered by PVDF fibrous layer on one side and by PA fibrous layer on the opposite side. Dielectric properties were examined and the triboelectric response was investigated in a simple triboelectric nanogenerator (TENG) of individual or combined (i-iv) fibrous structures. The highest triboelectric output voltage was observed for the stratified three-layer structure (the structure of iv type) consisting of PVDF and PA individual and intertwined fibrous layers. This TENG generated 3.5 V at peak of amplitude at 6 Hz of excitation frequency and was most sensitive at the excitation signal. The second highest triboelectric response was observed for the individual PVDF fibrous mat, generating 2.8 V at peak at the same excitation frequency. The uniqueness of this work lies in the dielectric and triboelectric evaluation of the fibrous structures, where the materials PA and PVDF were electrospun simultaneously with two needles and thus created a fibrous composite. The structures showed a more effective triboelectric response compared to the fibrous structure electrospun by one needle.

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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.

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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 BaTiO3 particles as cores and porous PVDF-TrFE as shells, the acoustic harvest devices with ingenious core-shell structures exhibit outstanding piezo-triboelectric properties (Voc = 15.24 V, DAsc = 9.22 mA/m2). The acoustic harvest principle reveals that BaTiO3 nanocores 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.

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Coating of steel is a frequently applied approach to increase the resistance of moving machine parts towards abrasion, surface oxidation, and corrosion. Here, we show that plating circular saw blades with certain metals can help to reduce the electrical charging of wood dust during cutting, which has significant implications for occupational safety, healthcare, and lifetime of filter systems. With the example of beech wood planks, machine net energy consumption EV (J cm-3) and cumulated field strength E→V (kV m-4) as caused by electrically charged particles were compared for cutting of 10- and 20-mm deep grooves (800 mm length) using saw blades of different toothing (24, 60 teeth) and surface coating (Cu, Ag, and Cr). To ensure uniform feed per tooth (fz = 0.063 mm), saw blades were operated at different rotation speeds (4000 vs. 1600 rpm). The results demonstrate that the extent of electrostatic sawdust charging can be manipulated to a certain extent by the type of saw blade plating. Coating with chromium turned out to be most effective in shifting the electrostatic charge of the wood particles towards neutralization. Lowering of rotation speed using circular saw blades of higher toothing was an additional measure significantly reducing electrostatic charging of wood dust. Hence, cutting with a chrome-coated blade with 60 teeth can be specifically recommended as the reduction of electrical saw dust charging is not associated with higher machine power consumption.