| The non-invasive diagnosis technique has became one of the research focuses in biomedical engineering nowadays. It is a promising method for lung cancer diagnosing by measuring 22 kinds of volatile organic compounds (VOCs) in the exhalent breath, such as styrene, decane, n-undecane.In this paper, we proposed a novel gas sensor─surface acoustic wave (SAW)gas sensor. It has the characteristcs of high sensitivity, high integration, good consistency, and can be used in many fields. Based on the mass deposition effect, we designed a sort of delay line SAW gas sensor, which has 51. 9MHz center frequency, 2. 1MHz bandwidth, high Q value (24. 36), low insert loss (-7. 86dB).4 kinds of sensing membranes had been studied and selected for detecting the VOCs in breath, in which, 22 kinds of VOCs are the markers of lung cancer. Meanwhile, we had explored a sort of membranes immobility technique-spin coating, by which themembrane can reach to 500nm thick.The key of this project is to design an electronic nose system for lung cancer diagnosis. A system composed of sampling part, testing part, calculating and identifying part was developed. Pre-concentration and separating techniques were used in the sampling part, and in the test part, the test and transfer frequency were measured by micro-controller, in the calculating and identifying part, artificial neural networks (ANN) was used to processing the data. We have also established an accute and effective calibrating system-gas chromatography and solid phase micro extraction (SPME).We cooperated with the Sir Run Run Shaw Hospital, sampled and tested some lung cancer patients' exhaled gas, and found there have some pertinence between lung cancer and VOCs.By the experiments, we have got data response of the SAW gas sensor to styrene and decane gases. It can be reach to the limit of 1ppm. From those data, we can get the conclusion that electronic nose using SAW gas sensor array is a promising method. |
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