Optimizations of composited acoustic sensors with a microfluidic channel

Abstract

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.

Theoretical Simulation and Optimization on Material Parameters of Thin Film Bulk Acoustic Resonator

“…eff can be evaluated by (8). However, 2 eff is not only determined by 2 but also closely related with the electrode and resonator structure.…”

“…The thin film bulk acoustic resonators (FBARs) are extensively applied for filters, resonators, and sensors, since they were first realized with the resonance frequency of 1.9 GHz in 1999, such as MEMS, biosensors, and gas sensors [1][2][3][4][5][6][7][8]. It is a kind of important device in electronic equipment, and so many kinds of FBARs with high frequency and small dimension have been fabricated during recent ten years for the demand of the industry [9,10].…”

Investigations of coupling acoustic matching in multilayer acoustic structures

“…For example, a multilayer acoustic resonator with a microfluidic channel is designed to realize liquid detections. 10 In the liquid acoustic sensor, the matching layers are to transmit the longitudinal acoustic energy from the piezoelectric layer into the substrate through a microfluidic channel, as shown in Fig. 1.…”