This study developed an inexpensive and simple microsensor for detecting volatile organic compounds (VOCs). This developed VOC sensor is composed of a nano-porous polyimide (PI) film doped with carbon black (CB) as the sensing material. The conductivity of the PI/CB film changed after absorbing VOC contents in the air. In general, solid state based VOC sensors which use metal oxide as the sensing materials have to work at a temperature of about 300¡V350¢J. Alternatively, this research developed a VOC sensor capable of sensing VOCs at room temperature, resulting in a sensor system of low energy consumption. A post pore opening procedure by plasma etching is used to enhance the response of the sensor film. SEM images confirm that the micro-pores interconnect with their neighboring pores and also open to the outside air. The film prepared with pore opening procedure exhibit a response of 3 times faster than the film prepared without pore opening. Results indicate that the developed VOC sensor has a good repeatability for detecting VOCs. PI film with 1% (weight percent) of CB has the best sensitivity due to the well dispersion of CB. This research detected 100 ppm ethanol fifth times to show good reproducibility, and detected 10 ppm, 100 ppm, 1000 ppm benzene and ethanol for 24 hours to show long-term stability, and detected 101 ppm¡ã105 ppm widely VOCs concentration. Besides, this sensor has selectivity on specific gas like alcohol and aldehyde, the sensor material has special chemical bond that can connect with specific gas. Moreover, the sensitivity is about 155% at 25 oC and 80% at 60 oC, it is almost 2 times at 25 oC. The moisture can also be detected to avoid the impact on the sensor performance for detecting VOCs, the moisture capacitance changes is 16 times higher than VOCs. The sensor developed in this study provides a simple and straight forward method to fabricate low-cost VOC sensors.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0617111-125027 |
| Date | 17 June 2011 |
| Creators | Ku, Yi-hang |
| Contributors | Shiao-wei Kuo, Chia-Yen Lee, Che-hsin Lin, Ying-chung Chen, Lung-ming Fu |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0617111-125027 |
| Rights | restricted, Copyright information available at source archive |
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