Research On Preparation And Performance Of Flexible Pressure Sensor Based On PDMS/PVA

Human skin is the main medium for human contact with the outside world.It can convert external signals,such as pressure,temperature and other complex environmental stimuli,Converted into physiological signals and transmit them to the brain,so that we can feel this stimulus.The flexible electronic skin can mimic the sensory function of human skin.In order to realize the application of electronic skin in wearable devices,a series of problems such as the selection of functional materials,the manufacturing process and the multifunctionalization of sensors must be solved first.This is also the challenge facing the development of flexible wearable devices.Aiming at the problems faced by flexible sensors.This paper selects stretchable and biocompatible materials PDMS and PVA-based hydrogels as flexible materials,and uses template method and 3D printing technology as the manufacturing process to prepare high sensitivity,flexible multifunctional sensor,and detailed research on sensor characteristics and applications.The details are as follows:（1）Flexible pressure and temperature sensors with complex leather structure.A stretchable and highly sensitive pressure sensor is prepared by template method,using leather as a mold and using stretchable and biocompatible material PDMS as a flexible substrate.The complex layer morphology of the leather makes the sensor have high sensitivity(7.76/k Pa^-1),wide detection range（0-400 k Pa）,fast response time（132 ms）and excellent service life（10000 cycles life）.It can accurately detect various human activities,such as finger bending,pulse,etc.The sensor has the ability to sense temperature in the temperature range of 23-90℃.By printing thermochromic materials on the surface of the sensor,the sensor provides intuitive color changes in a wide temperature range（18℃-40℃）.（2）Temperature and strain sensor based on silk fibroin/polypyrrole/PVA hydrogel.A dual-network antifreeze conductive hydrogel with PVA as the first network,silk fibroin as the second network,polypyrrole as the conductive filler,and water/ethylene glycol binary solvent as the dispersion medium is prepared by the cyclic freezing/thawing method.The response of the conductive hydrogel to external stimuli was studied.The hydrogel has considerable stretchability（860%）and withstands various deformations（tension,compression,etc.）.Under environmental conditions,good self-healing properties（more than 100%mechanical strength）can be achieved.It has high temperature sensitivity as high as 2.35%/℃in a wide temperature range from-10℃to 45℃.In addition,we propose a strategy to fabricate wearable pressure/strain sensors using 3D printing methods.The resulting pressure/strain sensor has higher sensitivity than the molding method（GF=7.12）.The pressure/strain sensor has a wide sensing range（strain:10%-706%;pressure:0.5-124.75 k Pa）.Sensor application and detection of human movements,such as the movement and bending of the little finger,pulse,etc.The sensor can distinguish English letters and numbers.It can also be used as an electronic pencil to operate an i Pad or smartphone with a capacitive screen.（3）Multifunctional sensor based on CNTs/silk fibroin/polypyrrole/PVA 3D printing ink.On the basis of the previous part of the work,by adding CNTs,a conductive hydrogel ink with shape retention capability and high resolution is prepared and applied to the preparation of flexible wearable devices.Tailor-made“bracelets”and“artificial skins”that are environmentally resistant and self-healing are printed,and the sensing properties and applications of artificial skins are studied.“Artificial skin”has the characteristics of sensing pressure,strain,temperature and humidity and other functions and has a wide range of pressure（0-180 k Pa）,strain（0-250%）,temperature（-20-68℃）and humidity（34.6-82%）sensing range and high sensitivity.It can be used to detect the tiny movements of the human body,and can also monitor changes in temperature and humidity,distinguish between hot and cold water,and perform detection of water droplets.The integrated electronic skin array can accurately detect temperature and pressure changes at the same time.After self-healing,the device can fully recover its sensing capabilities.This can effectively extend the service life of the sensor in practical applications.