Research On The Flexible Sensors Based On LCP

MEMS is an interdisciplinary research area which is based on the development of microelectronics technology.Microelectronics and micro-machining technology are adopted in the fabrication of MEMS sensors.Compared with traditional sensors,MEMS sensors have many advantages such as small size,light weight,low cost,low power consumption,high reliability,suitable for mass production,easy integration and intelligent.However,MEMS sensors based on rigid substrate have a lot of limitation in applications because they do not have the features of mechanical flexibility.Flexible sensors have so good flexible property that can be installed on in unflatten surface.Many flexible materials have been used in flexible sensors.LCP(Liquid Crystal Polymer)is one of them.Herein,two types of sensors have been developed based on LCP substrate:(1)flexible strain sensors;(2)flexible humidity sensors.(1)LCP was used in a flexible strain sensor.We took advantage of LCP as the flexible substrate and graphene as the strain sensitive material.The flexible strain sensor has a high sensitivity.The gauge factor of the flexible strain sensor is up to 375?473 which is higher than that of most recent researches.Static tests,dynamic tests and reliable tests of the flexible strain sensor were performed and the performance of the flexible strain sensors are so stable that could be applied in SHM(structural health monitoring).(2)LCP has been used in a flexible humidity sensor.We took advantage of LCP as the flexible substrate and polyimide as the humidity sensitive material.Compared with conventional humidity sensors based on silicon(Si)substrate the flexible humidity sensor has advantages of low cost,simple structure and easy fabrication process.The average sensitivity and the maximum hysteresis of the humidity sensor are 0.4fF/%RH and ±4.16%RH,respectively at 25 ?.The average sensitivity of the humidity sensor is hardly affected by the temperature in the range of 25?-70?.In addition,the response time and recovery time of the flexible humidity sensor are 36s and 39s,respectively.This flexible humidity sensor can be applied in environmental humidity monitoring,artificial skin and wearable devices etc.Above researches show that LCP,as a good flexible material,can be widely used in MEMS flexible sensors.