Publications

The Triboelectric Nanogenerator has demonstrated broad applications in energy, environmental, and electronic fields, as well as huge potential in the mechanism study of contact electrification, since 2012. Herein, we employed a Triboelectric Nanogenerator working in vertical contact-separation mode to study the electrification performance of the polymer under redox atmosphere. The results show that the electron-withdrawing ability of the polymer is weakened with increasing O3 concentration. Considering that O3 is typically one of the strongest oxidants, we further studied the electrification performance under H2, CO, and O2 atmosphere. It is found that the electron-withdrawing ability was predictably weakened under O2 atmosphere similar to the case of O3. On the contrary, the electron-withdrawing ability was enhanced under H2 and CO atmosphere. Accordingly, a theoretical mechanism involving the highest occupied surface state level is proposed to explain the effect of redox atmosphere on contact electrification. These results clarify that contact electrification can be varied by redox agents. Conversely, it also suggests the possibility to manipulate the redox reactions through the modification of contact electrification.

Abstract Tribovoltaic nanogenerators (TVNG) represent a fantastic opportunity for developing low‐frequency energy harvesting and self‐powered sensing, by exploiting their real‐time direct‐current (DC) output. Here, a thorough study of the effect of relative humidity (RH) on a TVNG consisting of 4H‐SiC (n‐type) and metallic copper foil (SM‐TVNG) is presented. The SM‐TVNG shows a remarkable sensitivity to RH and an abnormal RH dependence. When RH increases from ambient humidity up to 80%, an increasing electrical output is observed. However, when RH rises from 80% to 98%, the signal output not only decreases, but its direction reverses as it crosses 90% RH. This behavior differs greatly from that of a Si‐based TVNG, whose output constantly increases with RH. The behavior of the SM‐TVNG might result from the competition between the built‐in electric field induced by metal‐semiconductor contact and a strong triboelectric electric field induced by solid‐liquid triboelectrification under high RH. The authors also demonstrated that both SM‐TVNG and Si‐based TVNG can work effectively as‐is even fully submerged in deionized water. This mechanism can affect other devices and be applied to design self‐powered sensors working under high RH or underwater.

Nanogenerators (NG) have been developed to harvest mechanical energy from environmental sources such as vibration, human motion, or movement of automobiles. We demonstrate a robust and large-area NG based on a cost-effective Al substrate with the capability to be easily integrated in series and parallel for high-output performance. The output voltage and current density of the three-dimensionally integrated NG device reaches up to 3 V and 195 nA under human walking conditions.

As previously demonstrated, contact-electrification (CE) is strongly dependent on temperature, however the highest temperature in which a triboelectric nanogenerator (TENG) can still function is unknown. Here, by designing and preparing a rotating free-standing mode Ti/SiO2 TENG, the relationship between CE and temperature is revealed. It is found that the dominant deterring factor of CE at high temperatures is the electron thermionic emission. Although it is normally difficult for CE to occur at temperatures higher than 583 K, the working temperature of the rotating TENG can be raised to 673 K when thermionic emission is prevented by direct physical contact of the two materials via preannealing. The surface states model is proposed for explaining the experimental phenomenon. Moreover, the developed electron cloud-potential well model accounts for the CE mechanism with temperature effects for all types of materials. The model indicates that besides thermionic emission of electrons, the atomic thermal vibration also influences CE. This study is fundamentally important for understanding triboelectrification, which will impact the design and improve the TENG for practical applications in a high temperature environment.

Although MnO2 is a promising material for supercapacitors (SCs) due to its excellent electrochemical performance and natural abundance, its wide application is limited by poor electrical conductivity. Inspired by our results that the electrochemical activity and electrical conductivity of ZnO nanowires were greatly improved after hydrogenation, we designed and fabricated hydrogenated single-crystal ZnO@amorphous ZnO-doped MnO2 core-shell nanocables (HZM) on carbon cloth as SC electrodes, showing excellent performance such as areal capacitance of 138.7 mF/cm(2) and specific capacitance of 1260.9 F/g. Highly flexible all-solid-state SCs were subsequently assembled with these novel HZM electrodes using polyvinyl alcohol/LiCl electrolyte. The working devices achieved very high total areal capacitance of 26 mF/cm(2) and retained 87.5% of the original capacitance even after 10 000 charge/discharge cycles. An integrated power pack incorporating series-wound SCs and dye-sensitized solar cells was demonstrated for stand-alone self-powered systems.

The single domain insulator-to-metal transition in VO2 nanobeam triggered by coupling Joule heating and external strain is utilized to fabricate the high performance electromechanical switch, which can be controlled by stretching or compressing the substrate, and the device has the potential application in high sensitivity strain monitor and micro/nano-systems action control such as dynamic logic gate. Detailed facts of importance to specialist readers are published as "Supporting Information". Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Abstract Advances in implantable bioelectronics for the nervous system are reinventing the stimulation, inhibition, and sensing of neuronal activity. These efforts promise not just breakthrough treatments of several neurological and psychiatric conditions but also signal the beginning of a new era of computer‐controlled human therapeutics. Batteries remain the major power source for all implanted electrical neuromodulation devices, which impairs miniaturization and necessitates replacement surgery when the battery is drained. Triboelectric nanogenerators (TENGs) have recently emerged as an innovative power solution for self‐powered, closed loop electrical neurostimulation devices. TENGs can leverage the biomechanical activities of different body organs to sustainably generate electricity for electrical neurostimulation. This review features advances in TENGs as they pave the way for self‐sustainable closed loop neurostimulation. A comprehensive review of TENG research for the neurostimulation of brain, autonomic, and somatic nervous systems is provided. The direction of growth of this field, publication trends, and modes of TENG in implantable bioelectronics are also discussed. Finally, an insightful outlook into challenges facing self‐sustainable neuromodulators to reach clinical practice is provided, and solutions for neurological maladies are proposed.

Triboelectric Nanogenerators In article number 2101356, Tinghai Cheng, Zhong Lin Wang, and co-workers enhance the output performance of triboelectric nanogenerators via charge clamping (CC-TENG). The fabricated device consists of a mechanical-switch direct-current TENG, charge clamping module (CCM), and main-TENG. The accumulated charges flow in the loop circuit formed by the main-TENG and CCM, achieving an enhancement in the output performance.

Herein, we report a facile and robust route to nanoscale tunable triboelectric energy harvesters realized by the formation of highly functional and controllable nanostructures via block copolymer (BCP) self-assembly. Our strategy is based on the incorporation of various silica nanostructures derived from the self-assembly of BCPs to enhance the characteristics of triboelectric nanogenerators (TENGs) by modulating the contact-surface area and the frictional force. Our simulation data also confirm that the nanoarchitectured morphologies are effective for triboelectric generation.