Development of High Sensitivity Micro-Humidity Sensor based on Polyaniline
Date Issued
2008
Date
2008
Author(s)
Huang, Che-Wei
Abstract
Humidity is one of the most important parameters in various application fields, such as medical treatment and semiconductor industry. Therefore, there are many research groups focus on developing new humidity sensing materials. However, various limitations, such as high-temperature operations and complex fabrication process, impede the implementation of the developed humidity sensors. To overcome these obstacles, a novel humidity sensing material based on doped-polyaniline is developed in this work. In specific, this work demonstrates the developed humidity sensor with high linearity/sensitivity, high selectivity, low power consumption, fast response and room- temperature operations. Conducting polymers have many good material and mechanical properties, such as low cost, easy synthesis through chemical processes. Based on these advantages, hence, conducting polymers are one of the probable candidates for humidity sensing in practical applications. Consequently, we develop an innovative humidity sensing material based on the ferric-chloride/aluminum-chloride as dopants to improve the the doped polyaniline sensitivity and selectivity to the humidity. To prove the sensitivity characteristics of the developed sensor, the sensor device is placed in the controlled environment. As the device exposed to the different relative humidity (RH), the current flowing through the doped-polyaniline thin film is measured. The extremely low current obtained from the device reveals the low power consumption property. In addition, it should be noted that the device current increases two orders within a few seconds as the sensor exposed to the vapor. This fast response with the predictable linearity clearly illustrates feasibilities of the device for humidity sensing. Furthermore, the device is exposed to different gases including CO, N2 , CO2, C2H5OH, and NH3 to demonstrated the device selectivity. Apparently, the current difference generated by other kinds of gases is smaller than 12%. These experimental results demonstrate that the developed humidity sensor has high sensitivity, high selectivity, fast response, room- temperature operations and low power consumption. In this work, this newly developed doped polyaniline humidity sensor has been proved to have high sensitivity, repeatability and fast response characteristics. In addition, the simple fabrication process and interface circuit which decrease the manufacturing costs and improve the capabilities to be implemented into various applications. This investigation shows the developed polyaniline doped with Fe-Al ions has the potential to be applied to humidity sensing material in various aspects.
Subjects
humidity sensor
polyaniline
Type
thesis
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