Research On Polymer Electrolyte Humidity Sensor

With the development of modernization,humidity is becoming more and more closely related to human production and life,and the requirements for humidity monitoring and measurement are gradually increasing.In recent years,the field of flexible humidity sensors has achieved vigorous scientific research results.Among them,polymer electrolyte sensors have attracted a lot of attention from researchers because of their simple fabrication process suitable for mass production and their ability to be used in a wide range of humidity measurements.Compared with conventional humidity sensors,polymer electrolyte humidity sensors have the advantages of high sensitivity and short response time,but they also have the disadvantages of poor linearity and inability to work in high humidity environments,which limit their development.To solve this problem,this thesis constructs polymer electrolyte-based humidity sensors based on polyvinyl alcohol(PVA)film,cellulose acetate butyrate(CAB)film and CAB/PVA composite film using potassium acetate as the electrolyte.The main research work of the paper is as follows:Firstly,PVA and CAB were selected as the moisture-sensitive materials,and potassium acetate was used as the electrolyte to enhance the electrical conductivity and hydrophilicity of the films to improve the sensitivity of the sensors.PVA moisturesensitive films,CAB moisture-sensitive films and CAB/PVA composite moisturesensitive films were prepared by spin coating.Secondly,fourier infrared spectroscopy(FTIR),SEM morphological characterization,contact angle testing and correlation analysis were performed on the three different humidity sensing films.The FTIR analysis illustrated that the hydroxyl content of the moisture-sensitive films was enhanced after doping with potassium acetate.The SEM analysis concluded that the introduction of potassium acetate makes the moisture-sensitive films have a pore-like structure,which facilitates the adsorption and desorption of water molecules.The contact angle analysis shows that PVA has higher hydrophilicity than CAB,and the introduction of potassium acetate improves the hydrophilicity of the moisture-sensitive films.Thirdly,in the preparation of humidity sensor,PI-Ag flexible fork finger electrode is prepared by ion exchange and laser marking using PI as flexible substrate,and this method of preparing flexible electrode has the advantages of high efficiency,high precision and can be prepared in batch.On this basis,the humidity sensor is prepared and its moisture-sensitive performance is measured.Finally,a humidity sensor with a new double-layer composite structure using PVA-potassium acetate as the moisturesensitive layer and CAB as the protective layer is obtained,which has a fast response/recovery time and can also work in high humidity environments.Finally,the humidity sensor is applied for practical testing.A CAB/PVApotassium acetate humidity sensor with a better comprehensive performance is selected as a humidity sensing unit.The humidity is measured and transmitted to a cell phone terminal by an Arduino Uno microcontroller and CC2540 Bluetooth module.Then,the application on soil humidity detection is discussed.