Research On Humidity Sensor Based On Chitosan Semiconductor Polymer

Humidity is inseparable from human production and life,and the ability to achieve accurate humidity measurement is very important to all industries,such as the protection of medical equipment,planting of crops,monitoring of weather changes,and other fields.Most of the current humidity sensors are made of moisture-sensitive materials with low conductivity and weak water resistance,which makes it difficult to achieve accurate measurement of humidity.Therefore,in this thesis,we use the polymer material chitosan(CS)as the base material to prepare resistive chitosan(CS)/tin-dioxide(SnO₂)humidity sensors,chitosan(CS)/graphene oxide(GO)humidity sensors,and chitosan(CS)/graphene oxide(GO)humidity sensors,respectively.(GO)/tin dioxide(SnO₂)humidity sensors,and to investigate their moisture-sensitive properties.The main work of this thesis is as follows.(1)CS thin film and CS/SnO₂ composite sensitive thin film humidity sensors were prepared by solution blending method and vacuum evaporation method,and the pure CS thin film and CS/SnO₂ composite film were characterized and analyzed by characterization means and tested for their moisture-sensitive properties.The results showed that the moisture-sensitive characteristics of the CS/SnO₂ composite film were greatly improved compared with the pure CS film.The sensitivity of the CS/SnO₂composite film was 93.09 and that of the pure CS film was 45.46,and its response/recovery time was 158s/100s with a wet hysteresis value of about 7%RH,which had good repeatability and stability.Its responsiveness at higher relative humidity(RH)is 1.63 times higher compared to the pure CS film.Finally,the sensing mechanism of the moisture-sensitive material is discussed and analyzed.(2)CS/GO humidity sensors were prepared by solution blending and brush coating methods,and the prepared CS/GO composite films were characterized and tested by thin-film characterization methods.The results showed that the responsiveness and sensitivity of CS/GO composites with different mass fractions were very different.Among them,the sensitivity of the composite film with 10 wt%CS/GO is 112.17,the wet hysteresis value is lower at around 5%RH,the response time is 146 s,the stability and repeatability are good,and the responsiveness is also greatly improved compared with that of pure CS.Finally,the humidity response mechanism of CS/GO composite was analyzed.(3)A humidity sensor of CS/GO/SnO₂ composite film was prepared,and the CS/GO/SnO₂ composite film was characterized and analyzed using film characterization and the humidity characteristics of the composite film were tested,and the results showed that the humidity sensitivity of the CS/GO/SnO₂ composite film compared to the CS film,the CS/SnO₂ composite film and the CS/GO composite film was greatly improved.The sensitivity of CS/GO/SnO₂ composite film is 113.56,the response/recovery time is95s/140s,and the moisture hysteresis is around 2%RH,possessing very good repeatability and stability.Finally,the humidity-sensitive response mechanism of the CS/GO/SnO₂ composite film high-sensitivity humidity sensor was analyzed.