Capacitive Flexible Pressure Sensor Based On Hierarchical Microstructure

With the development of artificial intelligence,wearable electronics,biomedical engineering and other fields,people's need with flexible,high-performance sensor devices are also increasing.Flexible pressure sensor as one of the most widely used sensor,has received much attention in recent years,and become a new research hotspot.Generally,flexible pressure sensors are obtained by integrating organic or inorganic electronic materials onto flexible substrates,and a certain microstructure is adopted to obtain higher performance which is not less than or even more than the traditional rigidity divice.The research on different types of flexible pressure sensor is generally focused on the substrate material,the selection of pressure-sensitive materials,device structure design,device manufacturing process,in order to obtain higher performance,wider range of applications.There are several types of flexible sensor,such as capacitive,piezoresistive,piezoelectric and so on.The capacitive flexible pressure sensor has the advantages of temperature stability,great dynamic response,detecting the static pressure and low pressure,gained extensive research.In this paper,a series of study on capacitive flexible pressure sensor is carried out to improve the sensitivity of sensor at the low pressure range,force measurement range,and sensor performance for different application scenarios.In addition,the finite element simulation software Abaqus is used to simulate the pressure and strain of the hierarchical microstructure.Based on the simulation results,we can conclude that the sensor with hierarchical microstructure is more sensitive in the low pressure range,and has wider measuring range.We further verify the performance of the sensors.The number of levels and the ratio of different levels have different effects on the performance of the sensors.Besides,we found hierarchical sensor has better performance,and adjusting the ration of different levels can regulate the performance.In addition,the sensitivity of the sensor reaches 5 kPa-1,and the low pressure detection threshold reaches 0.1 Pa,which reaches the lowest value reported in the literature.The sensor exhibits high repeatability when exerting 100 repeated 0-80 kPa pressure.And the sensor response is highly repeatable and reproducible up to 2000 cycles with excellent performance.Finally,we study the application of sensors in wearable devices and health monitoring.At present,the pulse monitoring sensor needs a certain background pressure,impede blood flow,which is not conducive to long-term monitoring.We use the low pressure extremely sensitive sensor to monitor the pulse without background pressure,and achieved good results.