Optimizations of composited acoustic sensors with a microfluidic channel.

An acoustic sensor with composited transmission and reflecting structure is investigated for detection in liquid medium, in which a temperature compensational layer is deposited on the Si wafer to create a low temperature coefficient of frequency. This type of structure regulates most acoustic energy into the substrate, i.e., Si wafer and the compensational layer. Consequently, the standing resonant vibrations in the substrate are induced, as its thickness is integer multiples of a half wavelength. The acoustic sensor shows a low frequency shift with temperature, and the temperature coefficient of frequency can be controlled to about zero at the room temperature. Additionally, the acoustic sensor for the liquid detection on the viscosity and mass can be estimated 35 kHz/Pa . s and 23.25 kHz cm2/ng, respectively. © 2014 AIP Publishing LLC. [ABSTRACT FROM AUTHOR]