Study Of Self-Powered Gas Sensing System Based On Impedence Matching Effect Of Triboelectric Nanogenerator

With the rapid development of internet of things?IOTs?technology,a large number of independent sensors are replacing traditional discrete sensors,and applied to intelligent monitoring in the IOTs.The demand for reliable,independent,minimization,sustainable,maintenance-free,wireless,multi-functional,and continuous operation of the sensing networks is rapidly growing.However,for continuous working sensors,the problems of the present power supply hinder their application and development.Triboelectric nanogenerator is a device which collects all kinds of mechanical energy in the environment and transforms it into electric energy.It has the advantages of low cost,easy production,less environmental pollution and sustainability.A large number of self powered sensing systems based on triboelectric nanogenerator have been proposed.Among the various sensing systems,self-powered triboelectric gas sensing systems have the most important applications in air quality monitoring,human health testing,military and aerospace applications,and are expected to be applied in wireless and intelligence IOTs to monitor various gas conditions in the future.TENG,from another perspective,can be treated as a self-powered sensing device by analyzing the electrical output signals?including output voltage and current?and information on the mechanical input?magnitude and frequency?.The triboelectric materials can also be treated as the gas sensing materials in the present self-powered gas sensing system.However,there still exists some limitations that restrict their practical applications.Firstly,the ambient environment,including temperature,humidity,motion frequency and amplitude all affect the output electric signals and disrupt the sensing signals,resulting in a poor selectivity,stability and reliability.Secondly,the requirements of materials both having triboelectric and gas-sensing properties seriously limit the selection of functional materials.Thirdly,external monitoring circuits are required to collect the signal generated by TENG,which means they are not genuinely and authentically self-powered systems.Thus,in this thesis we develop a stable and reliable TENG based authentic self-powered system for gas sensing applications.In this work,a triboelectric self-powered gas sensing system has been demonstrated by introducing a novel strategy of TENG based on coupling triboelectric effect and chemoresistive effect.The whole system is constructed by connecting TENG as energy harvester with a resistance-type gas sensor in series and and commercial LEDs in parallel as alarms.The detailed contents are shown as following:?1?The working mechanism of a self-powered sensing system based on triboelectric nanogenerator was investigated by connecting a vertical contact-separate mode TENG as energy harvester with a various load resistance in series.The working mechanism can be ascribed to the specific output characteristics of the TENG tuned by the load resistance of the gas sensor.Three working regions are marked according to the specific output characteristics of whole system.?2?A triboelectric self-powered vehicle emission test system was fabricated based on coupling triboelectric effect and chemoresistive effect.The whole system is constructed by connecting a vertical contact-separate mode TENG as energy harvester based on automobile engine vibration or vehicle bumps with a resistance-type NO₂ gas sensor in series as exhaust detector and commercial LEDs in parallel as alarms.The output voltage of TENG varies with the variable working states of gas sensors and then directly reflects on the on/off status of the LEDs.When introducing with 100 ppm NO₂,the resistance of gas sensor increases from 68 K?to 10 M?and the output voltage of TENG increases to 28 V,lighting up the LEDs.?3?A triboelectric self-powered hydrogen test system for hydrogen energy vehicle based on coupling triboelectric effect and chemoresistive effect was also demonstrated by connecting TENG and the hydrogen sensors at room temperature.A free-standing-triboelectric-layer mode TENG works as energy harvester based on wind energy when the hydrogen energy vehicle is moving.At the same time,a resistance-type H₂ gas sensor is connected with TENG in series and commercial LEDs in parallel as alarms.We also developed the Interdigitated electrodes to increase the output of current and change the distribution of three working regions.When introducing with 1000 ppm H₂,the resistance of gas sensor decreases from 300 K?to60 K?and the output voltage of TENG decreases to 8 V,making the LEDs inoperative.