Abstract
Statistical data says that people exposed to secondhand smoke (SHS) have a higher risk of getting lung cancer and coronary heart disease. The research goal is making a cigarette sensor by surface acoustic wave (SAW) to prevent from tobacco hazards. In order to detect low concentration of cigarette marker, sensitivity and stability are two important issues. The SAW sensor is coated with oxidized hollow meso-porous carbon nano-sphere (O-HMC) to replace generally used polymer as new type sensing material, which is more sensitive than poly-acrylic acid due to the much more carboxyl group bonded by HNO3 treated, increasing the sensitivity of 3-EP from 37.8 to 51.2 Hz/ppm and also preventing the drawbacks of polymer based sensing material, such as lack of thermal stability and swelling effect. An 800μL micro-chamber is designed for enhancing stability by blocking environmental interferences, and the HMC coated chip is used as control due to the higher similarity of surface state between experiment and reference would increase stability, finally the noise can down to 5 Hz. The small volume of chamber and the large surface area of sensing material, caused by porous structure is leading to rapid detection at the low flow rate of 20 mL/min. The SAW sensor successfully detects cigarette smoke with high sensitivity and good repeatability by filtering above 1μm particles and tar to solve the adhesion problem; as compared to four interfered gas, ammonia, methane, carbon monoxide and carbon dioxide, the SAW sensor has 5 times more selective to cigarette smoke. This SAW sensor also detects water vapor to remove the influence of humidity and uses the resulting trend line to calibrate the frequency shift by detecting cigarette. In addition to detect SHS, this research takes the same SAW detector to sense the thirdhand smoke (THS) on different clothing fabrics, such as wool, cotton and polyester, finally knows that wool will absorb the maximum amount of THS and get the longest residual time.