Study On The Application And Mechanism Of Energy Harvester And Tactile Sensor Based On Nano Zinc Oxide

With the development of nano materials and nano technology, the research of nano devices has made a great progress in recent years. The applications of nano devices have covered many fields such as machinery, electronics, energy, environment, biology, medicine and information security, etc. Among them, Zinc Oxide (ZnO) nano materials, as a kind of functional materials, with semiconductor properties, piezoelectric properties, good thermal stability and biocompatibility, have been widely used in the preparation of various functional devices. This nanomaterial has important research value in the fields of photoelectricity,piezoelectricity, thermoelectricity, ferroelectricity and so on. With the continuous progress of science and technology, the usage of portable electronic devices is a major trend, which has become an indispensable device in personal communication, personal health monitoring,environmental monitoring, etc. However, the power supply has become the key factor restricting the development of these wearable electronic devices. The devices based on ZnO materials show a strong potential in the application of wearable electronic devices, flexible display, electronic skin, self-powered sensing and so on.This dissertation has focused on ZnO functional material and carried out a series of research work around the principle analysis, structure design and device fabrication of energy harvester, triboelectric nanogenerator (TENG), and self-powered tactile sensor, the main contents include the following sections:(1) The application and mechanism research of vibrational piezoelectric energy harvester based on ZnO nano materialsFirstly, a new type vibrational piezoelectric energy harvester of tuning fork type cantilever was put forward. The performance of the vibrational piezoelectric energy harvester was simulated and analyzed through COMSOL software. The differences of the rectangular,triangular and tuning fork type energy harvester were compared at resonant frequency and output power. The influence of different structural parameters on the output performance was explored. On this basis, a layer of ZnO nanorods (NRs) was synthesized on the flexible Kapton substrate through a low temperature hydrothermal method, and was served as the functional layer of the tuning fork structural energy harvester. The device was fabricated and its performances were analyzed. The results show that the voltage and current output of the tuning fork structural energy harvester could reach 160 mV and 11 nA respectively, when the frequency of vibration table was 13 Hz, and the best matching impedance was approximately 9 MQ. The simulation results show that the designed tuning fork structure can effectively reduce the resonant frequency of the cantilever beam, and it can work at lower frequencies.(2) The application and mechanism research of TENG based on ZnO nano materialsIn order to enhance the performance of TENQ we presented a method on the surface modification of the functional layer of TENG based on ZnO microballoons, and explored the relationship between the output performance and the surface microstructure of functional layer through parallel-plate capacitor model. By comparing the micro structure of the plat panel, cuboid, cylinder and pyramid, the results show that the devices with pyramid structure demonstrate the best output performance. We fabricated a vertically-grown ZnO microballoon arrays on top of pyramid-featured PDMS patterned film to enhance the electric output of sandwiched TENG. Then the electrical performances of the designed TENG were studied through experiments. These results show that both the voltage and current are increasing with the frequencies of external forces. The corresponding output open-circuit voltage with ZnO microballoons could reach up to 57 V and a current density of ～59 mA/m2 at 100 Hz, which was about 2.3 times higher than that without any ZnO materials. And the global maximum of the instantaneous peak power density could get up to 1.1 W/ m2 when the external load resistor was about 2 MQ. Moreover, the electrical output could lighten thirty commercial LED bulbs without any rectifier circuits or energy-storage elements. Stability experiments show that the fabricated TENG has an unchanged voltage of about 57 V after 100000 cycles. It evidently suggests that this kind of surface modification can dramatically enhance the electronic output of TENG.(3) The application research of self-powered tactile sensor based on ZnO nano materialsIn this work, a flexible self-powered tactile sensor array was designed based on the piezoelectricity of ZnO NRs. First, the relationship between the electrical output performance and the model parameters of ZnO, such as diameter,length,density and so on was explored through multiphysics software based on the theory of piezoelectricity. Then,the field-limited ordered ZnO NRs were synthesized on flexible Kapton substrate to serve as the function layer of tactile sensor. After that, the electrical output responses of as-fabricated tactile sensor were measured under pressing and bending modes. The results show that the voltage output of the sensor has a good linear relationship with the external pressure within the range of 100 Pa -1 MPa, and when the external force is 1 MPa, the output voltage of the sensor could reach 0.32 V. In bending mode, the output voltage of the sensor was first increased and then decreased with the increase of squeezing distance, and the voltage of middle column of the sensor array could reach peak value 0.26 V when the squeezing distance is 15 mm. Moreover, we measured the human-finger pressure detection performance of tactile sensor array, suggesting that the corresponding mapping figure of finger pressure could be displayed on the monitor of personal computer (PC) in the forms of lighted LED and color density through Lab VIEW system. Furthermore, it could further realize large-area multi-point touch control, display, and self-powered sensing through a multi-channel DAQ system. The developed sensing array could realize self-powered flexible tactile sensing, which has important research value and wide application space.