Research And Development Of Piezoresistive Flexible Sensor Based On Suspended Single-walled Carbon Nanotube Array

Since their discovery in 1991, carbon nanotubes (CNTs) have attracted great interest for its exceptional mechanical properties, electrical properties and electro-mechanical properties. Especially in mechanical sensors, Single-wassed carbon nanotube (SWNT) has significant piezoresistive effect, if this can be applied to mechanics sensor, then the accuracy of the mechanics sensor will be greatly improved.In earier studies, taking advantage of the advanced equipment such as Atomic force microscope (AFM), Scanning electron microscope (SEM), Scanning transmission electron microscope (STEM), some properties of SWNT have been investigated with probe contact between the carbon nonotube and measuring circutis. Some research results on the fabrication and express of CNT have been reported. CNT-based field effect transitor, CNT-based logic unit, CNT-based sensors have been developed in the lab and show the better chacrateristcs than traditional components. However, An individual CNT device is difficult to be in application and thin film CNT devices have lower sensitivity for a variety of chirality mixing. Therefore, exploring application-oriented new sensing structure based on SWNT is the focus of this thesis.Firstly, investigation was made on current research status of piezoresistive mechanical sensors and piezoresistive effect of SWNT for the subject and then analysis of future application was made for SWNT to apply in piezoresistive mechanical sensors. Next, the content of this research project was determined.In this dissertation, aiming at the current research status, on the basis of understanding the structure and properties of SWNT, Proposed and successfully implemented the two key technologies of selectivity electrical breakdown SWNT array based on strain and neatly arrange SWNT array on bent flexible substrate by dielectrophoresis. And at the same time, the new technologies of preparation of SWNT, micro-nano fabrication and maskless selective electro-deposition were utilized. Finally, a micro-nano sensor structure with SWNT was developed and its preliminary electromechanical characteristics were measured. Results show that the preparation process can be used to develop high sensitity SWNT mechanical sensors and a certain application in the production area of micro-nano devices.The focus of the study is subjected to taking SWNT as sensing material, realizing the orderly alignment of SWNT arrays on flexible substrates with electrodes, so the suspended and stretched SWNT arrays can have the ability to measure negative strain, and then the method of strain-based electrical breakdown is used to improve the gauge factor (GF) of suspended SWNT arrays. The results show that this design method and steps achieve the desired purpose, the GF can reach 400, which is more than a GF of 240 currently owned by doped silicon piezoresistive force-sensitive sensor, and the linearity of the electromechanical characteristic curve of suspended SWNT array is better than 95%.Finally, the major contributions, innovations and conclusions were summarized, and the future researches and ideas were proposed.