Research On Resistive Flexible Pressure Sensor With Sensitive Microstructure

Flexible pressure sensor,as an important component of flexible electronic frontier technology,has gradually become one of the research hotspots with the rapid development of information technology.In order to meet the needs of different application scenarios,flexible pressure sensors should have high sensitivity,wide range and high stability.Although the resistive flexible pressure sensor has been widely concerned due to its simple structure,easy signal conditioning and good linearity,the contradiction between high sensitivity and wide range of the resistive flexible pressure sensor,the complex preparation process and the high cost limit its promotion in practical applications.In order to overcome the above problems,two kinds of resistive flexible pressure sensors with different sensitive microstructures were designed and fabricated,and their performance was tested.The main research contents and results are as follows:（1）Design and preparation of flexible pressure sensor with batten sensitive structure.Firstly,the mechanical finite element method is used to construct the mechanical model of the batten sensitive structure sensor with different sizes.The influence of the batten structure parameters on the sensitivity of the sensor is analyzed,and the size parameter optimization of the batten sensitive structure is completed.Secondly,according to the results of parameter optimization,the batten structure pressure sensitive layer of MWCNT/WPU conductive composites was prepared by mixed solution template method and printed circuit board（PCB）as the molding template.Finally,the pressure sensitive layer designed and prepared above is packaged with a single-sided interdigital electrode with polyimide（PI）as a flexible substrate to obtain a flexible pressure sensor with a batten structure.（2）Design and preparation of all-paper-based flexible pressure sensor.Mulberry paper with loose microstructure and filter paper with pore microstructure were selected as flexible substrates.Firstly,silver nanowires（Ag NW）with high conductivity were formed on the surface of filter paper by suction filtration process as upper and lower electrodes.The MWCNT conductive ink material was coated on the surface of mulberry paper by drop coating/dip coating process to prepare a pressure sensitive layer.Secondly,the effects of different process parameters and different conductive material contents on the surface morphology and electrical conductivity of the electrode and the pressure sensitive layer were studied,and the optimal process parameters and material selection were determined.The three layers of the same pressure sensitive layer were stacked and packaged with the upper and lower electrodes to obtain a paper-based flexible pressure sensor.（3）The characteristic test and application test of two flexible sensors were carried out respectively.For the flexible pressure sensor with batten sensitive structure,the sensitivity of the sensor can reach 46.66 k Pa^-1 in the range of 0-1.5 k Pa and 6.67 k Pa^-1in the range of 1.5-7.5 k Pa by virtue of the advantages of batten sensitive structure and material.It also has excellent stability and high durability after more than 500 cycles.The designed batten sensitive structure sensor can accurately measure the small pressure and realize the real-time monitoring of human physiological signals.The preparation method has the advantages of low cost,simple structure and high consistency,which plays a positive role in promoting the development of wearable devices and other related devices.For all-paper-based flexible pressure sensors,thanks to the porous network structure and pressure-sensitive layer stacking structure of mulberry paper,the sensor has high sensitivity of 6.26,4.69 and 1.707 k Pa^-1 in the pressure range of 0-50 k Pa,50-500 k Pa and500-1000 k Pa,respectively.The detection limit is as low as 1 Pa,and it shows excellent stability and repeatability in 1000 cycles of loading/unloading;the above characteristics indicate its broad application prospects in the field of wearable devices and the Internet of Things.