Publications

Abstract Triboelectric nanogenerators (TENGs) represent an emerging technology in energy harvesting, medical treatment, and information technology. Flexible, portable, and self‐powered electronic devices based on TENGs are much desired, whereas the complex preparation processes and high cost of traditional flexible electrodes hinder their practical applications. Here, an MXene/polyvinyl alcohol (PVA) hydrogel TENG (MH‐TENG) is presented with simple fabrication, high output performance, and versatile applications. The doping of MXene nanosheets promotes the crosslinking of the PVA hydrogel and improves the stretchability of the composite hydrogel. The MXene nanosheets also form microchannels on surfaces, which not only enhances the conductivity of the hydrogel by improving the transport of ions but also generates an extra triboelectric output via a streaming vibration potential mechanism. The measured open‐circuit voltage of the MH‐TENG reaches up to 230 V even in a single‐electrode mode. The MH‐TENG can be stretched up to 200% of the original length and demonstrates a monotonical increasing relationship between the stretchable length and the short‐circuit voltage. By utilizing the MH‐TENG's outstanding stretchable property and ultrahigh sensitivity to mechanical stimuli, applications in wearable movement monitoring, high‐precision written stroke recognition, and low‐frequency mechanical energy harvesting are demonstrated.

As an emerging power technology, triboelectric nanogenerator (TENGs) promote the development of self-powered portable electronic systems because they can harvest ambient mechanical energy with a variety of working modes. Nevertheless, the practical application of TENGs is still limited by their low output and poor mechanical durability, and it is still a challenge to fabricate fully sustainable TENGs with high performance. Herein, a spring-supported TENG based on multilayer stacked triboelectric electrodes is proposed, which has good mechanical stability and output performance because of the introduction of the stacked sponge buffer layer and the particle vibration layer. The as-obtained TENG shows remarkable output performance enhancement, and a peak open-circuit voltage of 1.85 kV and a maximal short circuit current of 90 μA are realized. The peak power reaches up to 26 mW, which can light up 475 LEDs. Additionally, the electric signals can also be utilized to monitor environmental stimuli, such as vibration and human movement; thus, a sustainable self-powered monitoring system may be developed. Furthermore, the device could also be used to develop smart homes on the basis of human–machine interaction, thus showing great potential for applications in the Internet of Things.

Abstract Review: 30 refs.

Vanadium dioxide is a key material for thermochromic smart windows that can respond to environmental temperatures to modulate near infrared irradiation from a transparent state at low-temperature to an opaque state at high-temperature while maintaining the visible transmittance. This paper reports a novel VO2/FTO/glass multi-layered structure, which shows promising optical properties for application to energy-efficient smart windows. VO2 thin films are deposited on F-doped SnO2 (FTO) glasses by annealing a precursor film that is obtained via a solution-based process. The rutile-structured FTO substrate enhances the crystallinity of the VO2 films and lowers the synthesis temperature to ∼390 °C. The VO2/FTO/substrate double-layered films show both improved low-emissivity performance and distinct thermochromic properties. For a 65 nm thick VO2/FTO substrate double-layered film, low emissivities of 0.19 and 0.27 before and after the metal-insulator phase transition (MIPT) are obtained, while a solar transmittance modulation efficiency (η, in the wavelength range of 280–2600 nm) of 4.9% is achieved. A TiO2 anti-reflective coating (ARC) is incorporated to form a three-layered TiO2/VO2/FTO/substrate structure to boost the integrated visible transmittance (Tvis) while maintaining the low-emissivity performance. A 29.4% improvement for Tvis from 34.0% to 44.0% at room temperature is achieved for a 55 nm thick VO2 film coated with a TiO2 layer while emissivities of 0.13 and 0.24 before and after MIPT are maintained. Moreover, η is also increased significantly, from 4.3% for the VO2/FTO/substrate structure to 8.8% for the TiO2/VO2/FTO/substrate structure. Our results demonstrate a new approach of combining both thermochromism and low-emissivity performance for applications such as VO2-based energy-saving windows.

On the basis of a vertically aligned ultralong Pb(Zr0.52Ti0.48)O3 (PZT) nanowire array fabricated using electrospinning nanofibers, we developed a new type of integrated nanogenerator (NG) with ultrahigh output voltage of 209 V and current density of 23.5 μA/cm2, which are 3.6 times and 2.9 times of the previous record values, respectively. The output electricity can be directly used to stimulate the frog's sciatic nerve and to induce a contraction of a frog's gastrocnemius. The NG can instantaneously power a commercial light-emitting diode (LED) without the energy storage process.

Abstract Touch sensing is among the most important sensing capabilities of a human, and the same is true for smart robotics. Current research on tactile sensors is mainly concentrated on electronic skin (e‐skin), but e‐skin is prone to be easily dirtied, damaged, and disturbed after repeated usage, which greatly limits its practical applications in robotics. Here, by mimicking the way that animals explore the environment using hair‐based sensors, a bendable biomimetic whisker mechanoreceptor (BWMR) is designed for robotic tactile sensing. Owing to the advantages of triboelectric nanogenerator technology, the BWMR can convert external mechanical stimuli into electrical signals without a power supply, which is conducive to its widespread applications in robots. Because of the leverage effect of the whisker, the BWMR can distinguish an exciting force of 1.129 μN by amplifying external weak signals, which can be further improved by increasing the whisker length. Real‐time sensing is demonstrated using a BWMR, exhibiting its potential for robotic tactile systems.

Abstract With great potential applications, triboelectric nanogenerator (TENG), is widely studied from various aspects, while systematic investigations about the effects of environmental atmosphere on its performance remain to be carried out. Here, a test system based on a piston‐structured TENG and one‐way valve gas line is built, employing the contact–separation mode. A series of tests about short‐circuit transfer charges ( Q SC ) and open‐circuit voltage ( V OC ) are studied among three kinds of dielectric materials (PTFE, Kapton, PET), in five pure gases (N 2 , O 2 , CO 2 , Ar, He). At a static gas flow rate of 3 L min −1 or static gas pressure of 6 kPa above 1 atm, multicycle statistics demonstrate that TENGs achieve the highest performance in CO 2 and the lowest in He. Meanwhile, Kapton‐based TENG shows the greatest disparity in different atmosphere, followed by PET‐based TENG, and PTFE‐based TENG. A microscale discharge mechanism is introduced to explain all the above. Moreover, a negative linear relationship between Q SC and the static gas pressure above 1 atm is found. This study is an important reference for a high‐performance TENG configuration and device packaging in the future.

The liquid-solid triboelectric nanogenerator is broadly studied for its self-powered sensing and blue energy harvesting, thanks to its low wear and highly efficient contact. However, the corresponding research studies focusing on deionized-water liquid-solid triboelectric nanogenerators (DL-TENGs) and seawater-type liquid-solid TENGs (SL-TENGs) are rarely being carried out at present. Here, a SL-TENG is fabricated by applying a dielectric film as the organic coating and coated and uncoated steel hull as the two electrodes. Based on the reasonable material selection of the dielectric film, the SL-TENG showed excellent performance, which benefits from the good triboelectrification performance and weak ion adsorption effect. In addition, compared with commercial marine anticorrosive coatings, the friction coefficient of the SL-TENG with the seawater can be reduced 43.8%, which is significantly beneficial to reduce the sailing resistance of ships. More importantly, the uncoated steel electrode can obtain a high potential in highly corrosive seawater, which can enable it to perform the function of marine anticorrosive agents. Our finding provides a potential strategy to evade the marine anticorrosion of ships.

The electric double layer (EDL) at liquid-solid interfaces is fundamental to many research areas ranging from electrochemistry and microfluidics to colloidal chemistry. Here, we demonstrate the electricity generation by mechanically modulating the EDL at the hydrogel-dielectric polymer interfaces. It is found that contact electrification between the hydrogel and the dielectric polymer could charge the dielectric polymer surface at first; the mechanical deformation of the pyramid-shaped hydrogel results in the periodic variation of the EDL area and capacitance, which then induces an alternative current in the external circuits. This mechano-to-electrical energy conversion mechanism is then utilized to construct soft stretchable self-powered pressure sensors by designing dynamic EDL at hydrogel-dielectric elastomer interfaces. The sensitivity is optimized to 1.40 kPa-1 in the low-pressure range of 31-300 Pa by increasing the elastomer roughness. Its antifreeze performance is also improved by adding ethylene glycol into the hydrogel. The capability in detecting subtle human activities is further demonstrated. This mechano-electrical energy conversion and the corresponding self-powered sensor can be widely applied in future soft electronics.