Publications

The next generation of materials needs to be adaptive, multifunctional and tunable. This goal can be achieved by metamaterials that enable development of advanced artificial materials with novel functionalities. There is arguably a critical shortage in research needed to engineer new aspects of intelligence into the texture of metamaterials for multifunctional applications. The goal of this study is to create a new generation of multifunctional composite mechanical metamaterials called self-aware composite mechanical metamaterial (SCMM) with complex internal structures toward achieving self-sensing and self-powering functionalities. We develop finely tailored and seamlessly integrated microstructures composed of topologically different topologically materials to form a hybrid sensor and nanogenerator mechanical metamaterial system. Experimental studies are conducted to understand the mechanical and electrical behavior of the multifunctional SCMM systems. We highlight how introducing the self-sensing and self-powering functionality into the material design could in theory lay the foundation for living engineered materials and structures that can sense, empower and program themselves using their constituent components.

Abstract A liquid–solid contact triboelectric nanogenerator (TENG) based on poly(tetrafluoroethylene) (PTFE) film, a copper electrode, and a glass substrate for harvesting energy in oil/water multiphases is reported. There are two distinctive signals being generated, one is from the contact electrification and electrostatic induction between the liquid (water/oil) and the PTFE film ( V TENG and I TENG ); and the other is from the electrostatic induction in the copper electrode by the oil/water interfacial charges (Δ V interface and I interface ), which is generated only when the liquid–solid contact TENG is inserted across the oil/water interface. The two signals show interesting opposite changing trends that the V TENG and I TENG decrease while the oil/water interfacial signals of Δ V interface and I interface increase after coating a layer of polydopamine on the surfaces of PTFE and glass via self‐polymerization. As an application of the observed phenomena, both the values of I TENG and I interface have a good linear relationship versus the natural logarithm of the concentration of the dopamine. Based on this, the first self‐powered dual‐signal detection of dopamine using TENG is demonstrated.

Ambient mechanical energy harvesting technology introduces a promising solution to alleviate expanding energy demands on a sustainable basis, of which the drawbacks should attract attention for further advances. In this work, a liquid-dielectrics interface based triboelectric nanogenerator (TENG) with direct-current output is reported as an energy harvester and a chemical sensor, with advantages of feasible fabrication, anti-wearing durability, and low energy consumption. The TENG consisting of an fluorinated ethylene propylene (FEP) tube and Cu electrodes is designed into a ring structure, with two electric brushes bilaterally anchored that converts an alternating-current output into direct-current output. The liquids and copper pellets as the fluid-state dielectrics are prefilled to generate triboelectric charges with an FEP tube. The relevant parameters of TENG are initially optimized, enabling a satisfactory output under rotating excitations. Furthermore, the inherent impacts of various liquids on the output performance of TENG are comprehensively studied, based on which chemical analysis system is developed. Meanwhile, the design for TENG with pellets is also modified for output-current enhancement. Finally, an assembled TENG has been demonstrated not only for energy harvesting without rectification but also for chemical detecting in liquid composition and moisture content analysis. The proposed TENG renders a more-efficient method for energy harvesting and greatly expands its application in direct-current self-powered systems.

Based on white light emission at silicon (Si)/ZnO hetrerojunction, a pressure-sensitive Si/ZnO nanowires heterostructure matrix light emitting diode (LED) array is developed. The light emission intensity of a single heterostructure LED is tuned by external strain: when the applied stress keeps increasing, the emission intensity first increases and then decreases with a maximum value at a compressive strain of 0.15–0.2%. This result is attributed to the piezo-phototronic effect, which can efficiently modulate the LED emission intensity by utilizing the strain-induced piezo-polarization charges. It could tune the energy band diagrams at the junction area and regulate the optoelectronic processes such as charge carriers generation, separation, recombination, and transport. This study achieves tuning silicon based devices through piezo-phototronic effect.

Abstract Visualization is a cornerstone in human–computer interaction, evolving from large screens to mobile devices and now to wearable display technology. However, conventional batteries and displays lack the softness and stretchability inherent to human skin. Here, a fully flexible, all‐in‐one electronic display skin by integrating a flexible microLED display, a stretchable circuit, and a Zn|PAM|V 2 O 5 hydrogel battery pack is developed. Vapor‐phase bulk transfer is used to efficiently and accurately transfer 10 000 microLEDs onto a flexible substrate, ensuring high flexibility and ultra‐thin (240 µm). The flexible hydrogel battery pack provides sustainable energy, with a high specific capacity of 331.3 mAh g −1 . Additionally, a transparent stretchable circuit board (maximum stretch 40%) is made by 3D printing technology. The skin display exhibited exceptional stretchability and biocompatibility, conforming to movements while maintaining high‐resolution dynamic visual outputs. These innovations pave the way for advanced skin‐implanted displays, promising transformative applications in information interaction, healthcare, and artificial intelligence.

A novel three-dimensional chiral network of TENGs, inspired by mechanical metamaterials, is designed to effectively harvest water wave energy, presenting flexibility, hyper-elasticity in water and wave-absorption behavior like metamaterials.

The physical behaviors of stationary cells, such as the morphology, motility, adhesion, anchorage, invasion and metastasis, are likely to be important for governing their biological characteristics. A change in the physical properties of mammalian cells could be an indication of disease. In this paper, we present a silicon-nanowire-array based technique for quantifying the mechanical behavior of single cells representing three distinct groups: normal mammalian cells, benign cells (L929), and malignant cells (HeLa). By culturing the cells on top of NW arrays, the maximum traction forces of two different tumor cells (HeLa, L929) have been measured by quantitatively analyzing the bending of the nanowires. The cancer cell exhibits a larger traction force than the normal cell by approximately 20% for a HeLa cell and approximately 50% for a L929 cell. The traction forces have been measured for the L929 cells and mechanocytes as a function of culture time. The relationship between cells extending area and their traction force has been investigated. Our study is likely important for studying the mechanical properties of single cells and their migration characteristics, possibly providing a new cellular level diagnostic technique.

A triboelectric sensor matrix (TESM) can accurately track and map 2D tactile sensing. A self-powered, high-resolution, pressure-sensitive, flexible and durable TESM with 16 × 16 pixels is fabricated for the fast detection of single-point and multi-point touching. Using cross-locating technology, a cross-type TESM with 32 × 20 pixels is developed for more rapid tactile mapping, which significantly reduces the addressing lines from m × n to m + n.

Abstract The recent discoveries of transition‐metal dichalcogenides (TMDs) as novel 2D electronic materials hold great promise to a rich variety of artificial van der Waals (vdWs) heterojunctions and superlattices. Moreover, most of the monolayer TMDs become intrinsically piezoelectric due to the lack of structural centrosymmetry, which offers them a new degree of freedom to interact with external mechanical stimuli. Here, fabrication of flexible vdWs p–n diode by vertically stacking monolayer n‐MoS 2 and a few‐layer p‐WSe 2 is achieved. Electrical measurement of the junction reveals excellent current rectification behavior with an ideality factor of 1.68 and photovoltaic response is realized. Performance modulation of the photodiode via piezo‐phototronic effect is also demonstrated. The optimized photoresponsivity increases by 86% when introducing a −0.62% compressive strain along MoS 2 armchair direction, which originates from realigned energy‐band profile at MoS 2 /WSe 2 interface under strain‐induced piezoelectric polarization charges. This new coupling mode among piezoelectricity, semiconducting, and optical properties in 2D materials provides a new route to strain‐tunable vdWs heterojunctions and may enable the development of novel ultrathin optoelectronics.