| Summary: | 碩士 === 國立清華大學 === 奈米工程與微系統研究所 === 105 === In this research, surface acoustic wave (SAW) is developed a highly sensitive electronic nose sensing system. 114 MHz SAW chips are fabricated by MEMS techniques in well design and processes; gold interdigital transducers are deposited on the 128° YX- LiNbO3. The physical adsorption of gas by sensitive coating material on delay lines and modulates the phase velocity of acoustic wave because mass loading effect .Using different frequency shift to identify the type and concentration of sample. Frist, the research detect single gas to construct database by different polymer. Eventually the goal of research use SAW array system measured unknown concentration of gas mixture.
In this research, the system used 2-ports sensors to detect gas mixture that increase to 4-ports sensors to detect it at same time. In order to detect low concentration of gas on two systems, sensitivity and stability are two important issues. The SAW sensor is coated with eight polymer (PNVP、P4VPy、P4VP、PMMA、PCL、PVB、PDMS and PS) to detect chemical compounds such as ammonia, methane and ammonia/methane mixture gases and find sensitivity and normalized. In ammonia, we found PNVP is higher than others. In methane, we found PMMA is higher than others. A 4-ports connecting micro-chamber is designed has replaced 800μL fluidic-chamber. An 4-ports connecting micro-chamber is designed for enhancing stability by blocking environmental interferences and uniformity of gas concentration and decrease gas line to increase detection efficiency. In addition, we test thermal stability and humidity on our sensors. It found that fixed temperature can improve stability and calibration.
For the future work, we hope increase database of single gas and increase quantity of sensor array is the most important target. And this SAW gas sensors has great potential in actual environment with wireless module and hope it’s can be widely used in daily life.
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