Humidity Sensor Based On Chitosan/Polyvinyl Alcohol Coated On The Surface Of Carbon Nanocoils

The measurement of relative humidity(RH)has important practical value in many fields,such as human health,agricultural production,industrial processing,storage and transportation,precision experiments,etc,and has been widely concerned and deeply studied by researchers.The accurate and rapid detection of relative humidity has become one of the important aspects of related research.In this work,the high humidity sensor was prepared by using the advantages of good electrical stability and strong water absorption of carbon nanocoil(CNC)combined with the hydrophilic material chitosan / polyvinyl alcohol to form a composite structure.This paper introduces the development history,classification and application of carbon nanomaterials,and the research status of humidity sensor of carbon nanomaterials at home and abroad.At the same time,the synthesis method,physical characteristics,structural characteristics of carbon nanocoil,as well as the structures and characteristics of various sensors made of carbon nanocoil are summarized and analyzed in depth.Combined with the characteristics of chitosan,polyvinyl alcohol and other humidity sensitive materials,a humidity sensor based on chitosan / polyvinyl alcohol coated on the surface of carbon nanocoil was prepared,and the test results were analyzed and discussed.The specific research results are as follows:1.The theory of water absorption by carbon nanocoil and composite membrane was analyzed.The conductivity was measured by proton jump between carbon nanocoil,chitosan and polyvinyl alcohol and water molecules when relative humidity(RH)changed.2.Based on PDMS,the sensor infrastructure covered with gold electrode and humidity sensitive material was prepared.By adjusting the configuration of carbon nanocoil dispersion and combining with electrophoresis,the controllable coating of CNC material was realized,and the humidity sensing unit based on carbon nanocoil was successfully prepared.3.A humidity sensor test platform is built to measure the change of normalized resistance under different humidity conditions.Under the condition of relative humidity of 45%-85%,the corresponding sensing characteristics are studied.It was found that the highest response value of the sensor with chitosan concentration of 2.5g/l was 13.3%,and that of the sensor with chitosan concentration of 7.5g/l was 19.3%.Four kinds of humidity are selected in the experiment,which are 55%,60%,70% and 80% respectively.Repeated experiments show that the change of normalized resistance is very small.In addition,the experimental humidity rise and fall cycle test results also show that the sensor has the advantages of good repeatability,high stability and short response time.Response time,repeatability and stability are good.4.In addition,the experiment also studied the corresponding sensing characteristics of the humidity sensor based on the surface of carbon nanocoil covered with polyvinyl alcohol under the condition of relative humidity of 45%-85%.The experiment found that the hysteresis of the sensor is small and the repeatability is good.However,whether from the normalization curve or response and recovery curve,the performance of the humidity sensor based on the surface of carbon nanocoil covered with polyvinyl alcohol is still to be improved compared with the chitosan humidity sensor.Therefore,the sensing structure has certain advantages,which can be used in a series of life production with high requirements for humidity lag effect.