Fabrication、Characterization And Application Of Pressure Sensor Based On PEDOT-coated Nonwoven Material

With the development of science and technology,smart textiles,wearable electronic devices and soft robots are now gradually entering our life and developing rapidly.The key component of wearable electronic devices is the flexible pressure sensor,which can sense the surrounding stimulus and give response to it.The selection of flexible substrates is quite important to fabricate a flexible sensor.Nonwoven material with unique three-dimensional structure,as well as high porosity,softness,flexibility and other characteristics,most importantly,it is easy to obtain and low-cost,make it a good candidate as a flexible substrate of a pressure sensor.Conductive polymers uniquely combined electrical properties of metals and excellent mechanical properties of polymers,have occupied an important position in the field of wearable electronics.Among them,3,4-ethylenedioxythiophene(PEDOT),which has high conductivity,feasibility of the processing techniques and the excellent stability under ambient conditions,has aroused the attention of many researchers.Therefore,this project attempts to load the conductive material PEDOT onto polyester nonwoven substrates to prepare flexible piezoresistive pressure sensors.The main research contents of this topic include:(1)Three routes for preparing PEDOT were used,including vapor phase polymerization(VPP),in-situ dipping(ISD)and solution deposition(SD)methods.The conductive polymer PEDOT was successfully coated on polyester nonwoven fabric and the prepared conductive PEDOT coated nonwoven material(PEDOT@NWF)was proved to have electrical conductivity and piezoresistive properties.(2)The control variable method is used to select the optimal conditions for the preparation of PEDOT@NWF composites.For each preparation method,factors that may affect the product properties,such as the concentration of reagents,reaction temperature and reaction time,were explored one by one to conclude the optimal parameters.The experimental results show that the different preparation methods have obvious influence on the plating of PEDOT on the substrates,cause different morphological state and other performance of the material.The samples made from in-situ dipping method have the largest amount of PEDOT coating and the highest fiber surface roughness.On the contrary,the samples made from solution deposition method have the least amount of coating and the fiber surface is the most polished.(3)The PEDOT@NWF composites prepared by three manufacturing processes were used to assemble pressure sensors and test their sensing performance respectively.The experimental results indicate that the PEDOT@NWF prepared by the VPP method(PEDOT@NWF-VPP)has the fastest response time(80 ms)and recovery time(40 ms).The sensor prepared by in-situ dipping(PEDOT@NWF-ISD)has the highest sensitivity in both small(0-4 kPa)and large(>4 kPa)pressure ranges(21.162 kPa-1 and 1.760 kPa-1 respectively),followed by the sensor prepared by vapor phase polymerization(PEDOT@NWF-VPP).PEDOT@NWF-VPP sensor and PEDOT@NWF-ISD sensor both have better washing resistance,higher operational stability and good compression fatigue durability,and can withstand repetitive compression(over 5000 cycles)at a pressure of 50 kPa.The compression stability of PEDOT@NWF-SD sensor is relatively poor.(4)Application-related testing of PEDOT@NWF pressure sensors are carried out.According to the experimental results,the PEDOT@NWF pressure sensor can provide accurate feedback on the physiological and limb activities of the human body,responding accordingly to different degrees of activity,from detecting minor stresses(e.g.,vibration of vocal cords,movement of laryngeal nodes,stretching of muscles and airflow)to detecting activities with large stresses(e.g.,bending of joints and monitoring of plantar pressure).It indicates that the sensor has great potential for human health monitoring,motor behavior monitoring,gait analysis and plantar pressure distribution analysis and many other applications.In summary,this project uses polyester nonwoven fabric as a flexible substrate,and successfully coated with conductive polymer PEDOT through three preparation methods,which gives the nonwoven material conductivity and piezoresistive properties.The flexible pressure sensor constructed by the as-prepared material has high sensitivity,fast reaction time,washability and good compression fatigue durability.The sensor is simple to prepare,low cost,and has great potential for applications in wearable electronic devices,smart textiles,and human motion behavior monitoring.