Publications

Energy harvesting from mechanical motions has immense applications such as self-powered sensors and renewable energy sources powered by ocean waves. In this context, the triboelectric nanogenerator is the cutting-edge technology that can effectively convert ambient mechanical energy into electricity through the Maxwell's displacement current. While further improvements of the energy conversion efficiency of triboelectric nanogenerators critically depend on theoretical modeling of the energy conversion process, to date only models based on single-relative-motion processes have been explored. Here, we analyze energy harvesting of triboelectric nanogenerators using a three-dimensional model in a linear-sliding mode and demonstrate a design of triboelectric nanogenerators that have a 77.5% enhancement in the average power in comparison with previous approaches. Moreover, our model shows the existence of a DC-like bias voltage contained in the basic AC output from the energy conversion, which makes the triboelectric nanogenerators an energy source more pliable than the traditional AC power generation systems. The present work provides a framework for systematic modeling of triboelectric nanogenerators and reveals the importance of obtaining direct analytical insight in understanding the current output characteristics of the triboelectric nanogenerators. Incorporating our model analysis in future designs of triboelectric nanogenerators is beneficial for increasing the energy conversion power and may provide insights that can be used in engineering the profile of the output current of the nanogenerators.

Using a two-end bonded ZnO piezoelectric-fine-wire (PFW) (nanowire, microwire) on a flexible polymer substrate, the strain-induced change in I−V transport characteristic from symmetric to diode-type has been observed. This phenomenon is attributed to the asymmetric change in Schottky-barrier heights at both source and drain electrodes as caused by the strain-induced piezoelectric potential-drop along the PFW, which have been quantified using the thermionic emission−diffusion theory. A new piezotronic switch device with an "on" and "off" ratio of ∼120 has been demonstrated. This work demonstrates a novel approach for fabricating diodes and switches that rely on a strain governed piezoelectric-semiconductor coupling process.

Respiratory sensing provides a simple, non-invasive, and efficient way for medical diagnosis and health monitoring, but it relies on sensors that are conformal, accurate, durable, and sustainable working. Here, a stretchable, multichannel respiratory sensor inspired by the structure of shark gill cleft is reported. The bionic shark gill structure can convert transverse elastic deformation into longitudinal elastic deformation during stretching. Combining the optimized bionic shark gill structure with the piezoelectric and the triboelectric effect, the bionic shark gill respiratory sensor (BSG-RS) can produce a graded electrical response to different tensile strains. Based on this feature, BSG-RS can simultaneously monitor the breathing rate and breathing depth of the human body accurately, and realize the effective recognition of the different human body's breathing state under the supporting software. With good stretchability, wearability, accuracy, and long-term stability (50,000 cycles), BSG-RS is expected to be applied as self-powered smart wearables for mobile medical diagnostic analysis in the future.

We report a size-manipulable synthesis of single-crystalline nanorods/nanowires of barium manganite (BaMnO(3)) and barium titanium manganite (BaTi(1/2)Mn(1/2)O(3)) by using the composite-hydroxide-mediated approach. The synthesis cleanly yields nanorods with a hexagonal perovskite structure. Typical nanorods have widths ranging between 50 and 100 nm, and the lengths can be easily controlled by time and temperature or by adding a small amount of water during the synthesis process. Resistance measurement shows that a phase transition happened at 58 K on BaMnO(3). The photoluminescence spectrum of BaTi(1/2)Mn(1/2)O(3) presents two emission peaks at wavelengths of 465 and 593 nm, corresponding to blue and green fluorescence. The ability to synthesize nanorod manganites of a desired length should enable detailed investigations of the size-dependent evolution of magnetism, magnetoresistance, nanoscale phase separation, and realization of a nanodevice of magnetic sensors.

There is increasing evidence that estrogen is responsible for improved outcomes in female kidney transplant recipients. Although the exact mechanism is not yet known, estrogen appears to exert its protective effects by ameliorating ischemia-reperfusion injury (IRI). In this study, we have examined whether the beneficial effects of exogenous estrogen in renal IRI are replicated by therapy with any one of several selective estrogen receptor modulators.C57BL/6 adult mice underwent standardized warm renal ischemia for 28 min after being injected with the selective estrogen receptor modulators, raloxifene, lasofoxifene, tamoxifen, bazedoxifene, or control vehicle (dimethyl sulfoxide), at 16 and 1 h before IRI. Plasma concentrations of blood urea nitrogen and creatinine were assessed 24, 48, 72, and 96 h post-IRI. Tissue was collected 30 d postischemia for fibrosis analysis using Sirius Red staining.Raloxifene treatment in female mice resulted in significantly lower blood urea nitrogen and creatinine after IRI and significantly lower fibrosis 30 d following IRI.Raloxifene is protective against both acute kidney injury and fibrosis resulting from renal IRI in a mouse model.

With the vigorous advancement of Ubiquitous Electric Internet of Things (UEIOT), online monitoring is essential for a stable operation of the transmission system. The energy supply that drives the monitoring system has become one of the bottlenecks restricting the development of distributed sensing systems. In view of the vibration with the characteristics of low-frequency and large-amplitude generated in the conductor galloping, a self-powered sensor has been proposed. This sensor consists of an electromagnetic generator (EMG), a horizontal TENG (H-TENG), and a vertical TENG (V-TENG) to provide an alternative approach for capturing mechanical energy derived from conductor galloping. Based on triboelectric–electromagnetic working principal, a sophisticated-designed stator and rotor structure oriented to the application scenarios of transmission lines successfully achieved self-power through the designed EMG and galloping state sensing through the designed H-TENG and V-TENG, respectively. The output performance of the hybridized nanogenerator was well validated on the linear motor platform and the conductor galloping test platform, and the output current was used to realize the characterization of the conductor galloping amplitude and galloping trajectory. This work not only provides an effective and sustainable solution to the self-powered intelligent sensor nodes in the complex surroundings of power transmission system, but also reveals TENG promising potential on the sensing applications in low-power monitoring sensors for conductor galloping.

Abstract The sliding‐mode triboelectric nanogenerator (TENG) exhibits higher charge transfer efficiency for extracting mechanical energy than the contact–separation mode TENG, but the energy loss induced by air breakdown as well as the inferior durability seriously limits its practical applications. Here, an effective strategy via interface liquid lubrication is proposed for enhancing output performance of both sliding‐mode alternative current TENG (AC‐TENG) and direct current TENG (DC‐TENG). Due to the improved breakdown field strength requirement and reduced electrostatic field strength in the microgap between the triboelectric layer and electrode, interface liquid lubrication suppresses the interfacial electrostatic breakdown and reduces charge loss after the triboelectrification process, and thus more electrostatic charges are harvested by the AC‐TENG via electrostatic induction and the DC‐TENG via electrostatic breakdown. The maximum output power density of the lubricated sliding‐mode TENG is enhanced by more than 50% (3.45 W m −2 Hz −1 ) compared to the device without lubrication, and shows excellent durability over more than 500 000 operation cycles. This work provides an effective approach to improve the electric performance and durability of sliding‐mode AC‐TENG and DC‐TENG, which further promotes the practical applications of TENGs.

Fractal hematite dendrites with structures resembling pine trees (see picture) were obtained by hydrothermal treatment of K3[Fe(CN)6]. They are formed by a novel process in which fast growth along six crystallographically equivalent directions forms dendritic or snowflakelike single-crystal structures, which differs from the mechanisms reported for other fractal structures.

The triboelectric effect is known for many centuries and it is the cause of many charging phenomena. However, it has not been utilized for energy harvesting until very recently. (1-5) Here we developed a new principle of triboelectric generator (TEG) based on a fully contacted, sliding electrification process, which lays a fundamentally new mechanism for designing universal, high-performance TEGs to harvest diverse forms of mechanical energy in our daily life. Relative displacement between two sliding surfaces of opposite triboelectric polarities generates uncompensated surface triboelectric charges; the corresponding polarization created a voltage drop that results in a flow of induced electrons between electrodes. Grating of linear rows on the sliding surfaces enables substantial enhancements of total charges, output current, and current frequency. The TEG was demonstrated to be an efficient power source for simultaneously driving a number of small electronics. The principle established in this work can be applied to TEGs of different configurations that accommodate the needs of harvesting energy and/or sensing from diverse mechanical motions, such as contacted sliding, lateral translation, and rotation/rolling.

Abstract It is of great importance to explore a creative route to improve the degradation efficiency of organic pollutants in wastewater. Herein, we construct a unique hybrid system by combining self-powered triboelectric nanogenerator (TENG) with carbon dots-TiO 2 sheets doped three-dimensional graphene oxide photocatalyst (3DGA@CDs-TNs), which can significantly enhance the degradation efficiency of brilliant green (BG) and direct blue 5B (DB) owing to the powerful interaction of TENG and 3DGA@CDs-TNs photocatalyst. The power output of TENG can be applied for wastewater purification directly, which exhibits a self-powered electrocatalytic technology. Furthermore, the results also verify that TENG can replace conventional electric catalyst to remove pollutants effectively from wastewater without any consumption. Subsequently, the unstable fragments and the plausible removal pathways of the two pollutants are proposed. Our work sheds light on the development of efficient and sustainable TENG/photocatalyst system, opening up new opportunities and possibilities for comprehensive utilization of random energy.

Dielectric elastomer generator (DEG) is a solid-state electrostatic device with variable capacitance. As an energy harvester, it should be passive, high performance, and fatigue-resistant. However, no such DEGs can satisfy these requirements simultaneously as the high performance strongly depends on a high external voltage and large capacitance change, which are prone to dielectric elastomer film fatigue and failure. In this study, we developed a passive alternating current dielectric elastomer generator (AC-DEG) to reconcile the contradiction and satisfy these requirements. Based on the AC method, a high performance by structural parameters could be obtained with a small capacitance change, which avoids the large capacitance change, and consequently, fatigue and failure. The AC-DEG exhibits energy density of 111 mJ/g with an energy conversion efficiency of 51.8% and charge density of 5.6 mC/m2 per cycle at 1.5 Hz with only a two-fold capacitance change. Furthermore, the AC-DEG can maintain over 100 mJ/g and 4.6 mC/m2 per cycle in a continuous operation for over 7 days (> 1 million cycles) at 1.5 Hz. We developed an integrated device with two AC-DEGs to charge commercial Li-polymer batteries with different capacities. This study provides an effective route for development of DEGs toward practical applications and industrialization.