Publications

Gyroscope-Structured Triboelectric Nanogenerator for Harvesting Multidirectional Ocean Wave Energy

Wave motion in the ocean can generate plentiful energy, but it is difficult to harvest wave energy for practical use because of the low frequency and random directional characteristics of wave motion. In this paper, a gyroscope-structured triboelectric nanogenerator (GS-TENG) is proposed for harvesting multidirectional ocean wave energy. Its inner and outer generation units can operate independently in different directions, and they all adopt the friction mode of surface contact. While realizing noninterference multidirectional energy harvesting, the power generation area is increased. In the experiments, under acceleration of 6 m/s2 with variations in excitation angle, the GS-TENG can output direct currents of 0.8-3.2 μA, and the open-circuit voltages of the inner and outer generation units can reach 730 and 160 V, respectively. When the devices are networked and placed in the water, the electrical energy generated by the GS-TENGs can enable commercial thermometers to operate normally. The attenuation of direct-current output by the GS-TENG in the experiment of 30 days in water is about 8%, which verifies the good durability of the device in the water environment. Therefore, the GS-TENG has excellent application prospects in the wave energy harvesting field.

Self-Powered Sensors and Systems Based on Nanogenerators

Sensor networks are essential for the development of the Internet of Things and the smart city. A general sensor, especially a mobile sensor, has to be driven by a power unit. When considering the high mobility, wide distribution and wireless operation of the sensors, their sustainable operation remains a critical challenge owing to the limited lifetime of an energy storage unit. In 2006, Wang proposed the concept of self-powered sensors/system, which harvests ambient energy to continuously drive a sensor without the use of an external power source. Based on the piezoelectric nanogenerator (PENG) and triboelectric nanogenerator (TENG), extensive studies have focused on self-powered sensors. TENG and PENG, as effective mechanical-to-electricity energy conversion technologies, have been used not only as power sources but also as active sensing devices in many application fields, including physical sensors, wearable devices, biomedical and health care, human-machine interface, chemical and environmental monitoring, smart traffic, smart cities, robotics, and fiber and fabric sensors. In this review, we systematically summarize the progress made by TENG and PENG in those application fields. A perspective will be given about the future of self-powered sensors.

Nanowires for Piezoelectric Nanogenerators

The nanogenerator (NG), first proposed for the purpose of self-powered nanotechnology in 2006, converts random mechanical energy into electric energy using piezoelectric zinc oxide nanowire (NW) arrays. The mechanism of the NG relies on the piezoelectric potential created in the NWs by an external strain: a dynamic straining of the NWs results in a transient flow of the electrons in the external load because of the driving force of the piezoelectric potential. The advantage of using NWs is that they can be triggered by tiny-scale physical motions. Further, the excitation frequency can range from one Hz to thousands of Hz, which makes NGs ideal for harvesting random energy in the environment. In our living environment, there exists an abundant amount of mechanical energy otherwise lost, such as light wind, body movement, muscle stretching, acoustic/ultrasonic waves, noises, mechanical vibration, and blood flow. Hence, the NW based piezoelectric NGs can provide a promising potential as energy harvester for solving the energy crisis and preserving environmental health. The objective of this chapter is to introduce the fundamentals of piezoelectric NW based NGs. We start from the synthesis of piezoelectric NWs, followed by a description of the fundamental principle of a NG based on a single NW. We then demonstrate the engineering approaches for achieving high output power by laterally and vertically integrating the contribution from thousands of NWs. Lastly, we show the prototype for self-powered systems and self-powered active sensors.

Wireless Joule nanoheaters

Fully Packaged Blue Energy Harvester by Hybridizing a Rolling Triboelectric Nanogenerator and an Electromagnetic Generator

Ocean energy, in theory, is an enormous clean and renewable energy resource that can generate electric power much more than that required to power the entire globe without adding any pollution to the atmosphere. However, owing to a lack of effective technology, such blue energy is almost unexplored to meet the energy requirement of human society. In this work, a fully packaged hybrid nanogenerator consisting of a rolling triboelectric nanogenerator (R-TENG) and an electromagnetic generator (EMG) is developed to harvest water motion energy. The outstanding output performance of the R-TENG (45 cm3 in volume and 28.3 g in weight) in the low-frequency range (<1.8 Hz) complements the ineffective output of EMG (337 cm3 in volume and 311.8 g in weight) in the same range and thus enables the hybrid nanogenerator to deliver valuable outputs in a broad range of operation frequencies. Therefore, the hybrid nanogenerator can maximize the energy conversion efficiency and broaden the operating frequency simultaneously. In terms of charging capacitors, this hybrid nanogenerator provides not only high voltage and consistent charging from the TENG component but also fast charging speed from the EMG component. The practical application of the hybrid nanogenerator is also demonstrated to power light-emitting diodes by harvesting energy from stimulated tidal flow. The high robustness of the R-TENG is also validated based on the stable electrical output after continuous rolling motion. Therefore, the hybrid R-TENG and EMG device renders an effective and sustainable approach toward large-scale blue energy harvesting in a broad frequency range.

Piezo-phototronics effect on nano/microwire solar cells

Wurtzite structures, such as ZnO, GaN, InN and CdS, are piezoelectric semiconductor materials. A piezopotential is formed in the crystal by the piezoelectric charges created by applying a stress. The inner-crystal piezopotential can effectively tune/control the carrier separations and transport processes at the vicinity of a p–n junction or metal–semiconductor contact, which is called the piezo-phototronic effect. The presence of piezoelectric charges at the interface/junction can significantly affect the performances of photovoltaic devices, especially flexible and printed organic/inorganic solar cells fabricated using piezoelectric semiconductor nano/microwires. In this paper, the current–voltage characteristics of a solar cell have been studied theoretically and experimentally in the presence of the piezoelectric effect. The analytical results are obtained for a ZnO piezoelectric p–n junction solar cell under simplified conditions, which provide a basic physical picture for understanding the mechanism of the piezoelectric solar cell. Furthermore, the maximum output of the solar cell has been calculated numerically. Finally, the experimental results of organic solar cells support our theoretical model. Using the piezoelectric effect created by external stress, our study not only provides the first basic theoretical understanding about the piezo-phototronic effect on the characteristics of a solar cell but also assists the design for higher performance solar cells.

Applicability of triboelectric generator over a wide range of temperature

Detection of Clarithromycin‐Resistant <i>Helicobacter pylori</i> by Stool <scp>PCR</scp> in Children: A Comprehensive Review of Literature

Helicobacter pylori infection is acquired mainly during childhood. To eradicate H. pylori, clarithromycin-based triple therapy has been recommended in children and adults by the latest Maastricht Consensus. However, the prevalence of clarithromycin-resistant H. pylori was higher in children than that in adults. Therefore, rapid, reliable and noninvasive methods for detecting clarithromycin-resistant H. pylori strains should be developed for children.Studies on evaluating stool PCR in detecting clarithromycin-resistant H. pylori and epidemiological surveys of the prevalence of clarithromycin-resistant H. pylori in children were searched in PubMed (from 1966 to December, 2011) for reviewing.The average rates of primary clarithromycin-resistant H. pylori ranged from less than 10% to more than 40% in different regions. The rates of secondary resistance to clarithromycin were higher than primary resistance in the same population. In H. pylori isolated from children, the frequent point mutations that are responsible for the clarithromycin resistance included A2143G, A2142G, A2142C and A2144G, and they varied geographically. Comparing with culture-based susceptibility tests, stool PCR performed excellently for their rapidity, independence of bacterial growth, reproducibility and easy standardization. However, stool PCR showed lower sensitivity but perfect specificity in detection of clarithromycin-resistant H. pylori in children. Methodology and mixed infections of resistant H. pylori strains might contribute to the considerable discrepancies of stool PCR results.Detection of clarithromycin-resistant H. pylori by stool PCR for children are reliable, rapid, noninvasive methods that are worthy of further clinical promotion. However, more evaluations of stool PCR in detection of clarithromycin-resistant H. pylori in children need to be conducted.

Self-powered electrochemical anodic oxidation: A new method for preparation of mesoporous Al2O3 without applying electricity

Integrated charge excitation triboelectric nanogenerator

Performance of triboelectric nanogenerators is limited by low and unstable charge density on tribo-layers. An external-charge pumping method was recently developed and presents a promising and efficient strategy towards high-output triboelectric nanogenerators. However, integratibility and charge accumulation efficiency of the system is rather low. Inspired by the historical development of electromagnetic generators, here, we propose and realize a self-charge excitation triboelectric nanogenerator system towards high and stable output in analogy to the principle of traditional magnetic excitation generators. By rational design of the voltage-multiplying circuits, the completed external and self-charge excitation modes with stable and tailorable output over 1.25 mC m-2 in contact-separation mode have been realized in ambient condition. The realization of the charge excitation system in this work may provide a promising strategy for achieving high-output triboelectric nanogenerators towards practical applications.

He-Wei granules inhibit chemotherapy-induced vomiting (CINV) in rats by reducing oxidative stress and regulating 5-HT, substance P, ghrelin and obestatin

As a common side effect of a variety of chemotherapy drugs, CINV severely limits the clinical use of chemotherapy drugs.

Intensity enhancement and plasmon inelastic scattering in RHEED

Enhanced Triboelectric Nanogenerators Based on MoS₂ Monolayer Nanocomposites Acting as Electron-Acceptor Layers

As one of their major goals, researchers attempting to harvest mechanical energy efficiently have continuously sought ways to integrate mature technologies with cutting-edge designs to enhance the performances of triboelectric nanogenerators (TENGs). In this research, we introduced monolayer molybdenum-disulfide (MoS2) into the friction layer of a TENG as the triboelectric electron-acceptor layer in an attempt to dramatically enhance its output performance. As a proof of the concept, we fabricated a vertical contact-separation mode TENG containing monolayer MoS2 as an electron-acceptor layer and found that the TENG exhibited a peak power density as large as 25.7 W/m2, which is 120 times larger than that of the device without monolayer MoS2. The mechanisms behind the performance enhancement, which are related to the highly efficient capture of triboelectric electrons in monolayer MoS2, are discussed in detail. This study indicates that monolayer MoS2 can be used as a functional material for efficient energy harvesting.

Enhancing UV photoconductivity of ZnO nanobelt by polyacrylonitrile functionalization

UV photodetector fabricated using a single ZnO nanobelt (NB) has shown a photoresponse enhancement up to 750 times higher than that of a bare ZnO NB after coating with ∼20nm plasma polymerized acrylonitrile (PP-AN) nanoscale film. The mechanism for this colossal photoconductivity is suggested as a consequence of the efficient exciton dissociation under UV illumination due to enhanced electron transfer from valence band of ZnO NB to the PP-AN and then back to the conduction band of ZnO. This process has demonstrated an easy and effective method for improving the performance of the nanowire∕NB-based devices, possibly leading to supersensitive UV detector for applications in imaging, photosensing, and intrachip optical interconnects.

Self-Powered System with Wireless Data Transmission

We demonstrate the first self-powered system driven by a nanogenerator (NG) that works wirelessly and independently for long-distance data transmission. The NG was made of a free cantilever beam that consisted of a five-layer structure: a flexible polymer substrate, ZnO nanowire textured films on its top and bottom surfaces, and electrodes on the surfaces. When it was strained to 0.12% at a strain rate of 3.56% S–1, the measured output voltage reached 10 V, and the output current exceeded 0.6 μA (corresponding power density 10 mW/cm3). A system was built up by integrating a NG, rectification circuit, capacitor for energy storage, sensor, and RF data transmitter. Wireless signals sent out by the system were detected by a commercial radio at a distance of 5–10 m. This study proves the feasibility of using ZnO nanowire NGs for building self-powered systems, and its potential application in wireless biosensing, environmental/infrastructure monitoring, sensor networks, personal electronics, and even national security.

Robust triboelectric-electromagnetic hybrid nanogenerator with maglev-enabled automatic mode transition for exploiting breeze energy

Phosphorus Doped Zn_1-<i>x</i>Mg_<i>x</i>O Nanowire Arrays

We demonstrate the growth of phosphorus doped Zn1-xMgxO nanowire (NW) using pulsed laser deposition. For the first time, p-type Zn0.92Mg0.08O:P NWs are likely obtained in reference to atomic force microscopy based piezoelectric output measurements, X-ray photoelectron spectroscopy, and the transport property between the NWs and a n-type ZnO film. A shallow acceptor level of ∼140 meV is identified by temperature-dependent photoluminescence. A piezoelectric output of 60 mV on average has been received using the doped NWs. Besides a control on NW aspect ratio and density, band gap engineering has also been achieved by alloying with Mg to a content of x = 0.23. The alloyed NWs with controllable conductivity type have potential application in high-efficiency all-ZnO NWs based LED, high-output ZnO nanogenerator, and other optical or electrical devices.

Piezophototronic Effect on Photon Sensors