Abstract: The present invention discloses a biosensor and a method using the same to perform a biotest. The biosensor of the present invention integrates a SAW (Surface Acoustic Wave) device and a test polymer to detect an analyte in a liquid specimen. The test polymer reacts with the analyte. After reaction, the substantial weight decrease of the test polymer causes the variation of the SAW characteristics. The attributes and content of the analyte is detected and determined according to the variation of the SAW characteristics.

Abstract: A gas sensor comprises a first surface-acoustic-wave device, at least one further surface-acoustic-wave device, and a control device. The first surface-acoustic-wave device includes a piezoelectric substrate, a pair of transducers and an external circuit. The pair of transducers consists of a first transducer and a second transducer, and they are formed on two sides of the piezoelectric substrate. The first transducer is utilized to generate a surface acoustic wave on the piezoelectric substrate. The external circuit electrically connects to the pair of transducers. At least one further surface-acoustic-wave device includes at least one first surface-acoustic-device and a sensing porous thin film of which two sides are formed on the pair of the transducers. The control device is utilized to control only one external circuit to become activated at one time.