Development of Love Wave-Based Ice Sensor Incorporating a PDMS Micro-Tank

Abstract

A Love wave-based sensing chip incorporating a polydimethylsiloxane (PDMS) micro-tank was proposed for ice sensing. The waveguide effect in the SU-8/ST-90°X quartz structure confines the acoustic energy in the SU-8 thin film, which is beneficial to improving the mass loading sensitivity and reducing longitudinal coupling attenuation in liquid. Self-compensation in temperature effect can be achieved by using the reverse polarity of the temperature coefficient (TCF) of SU-8 and ST-90°X. The micro-tank made of PMDS material was bonded on the acoustic wave propagation path to protect the interdigital electrodes and provide a sensitive area. Coupling of models (COM) and finite-element method (FEM) were employed to extract the optimal design parameters allowing low insertion loss of Love wave device, and the influence of PDMS toward Love wave propagation was also analyzed theoretically to determine the PDMS design. Using the standard photolithographic technique and molding method, a Love wave-based ice sensing chip was prepared to operate at 200 MHz and characterized by being connected to the amplitude detection circuit, and the corresponding icing sensing characteristics were studied. High sensitivity (11.894 mV/mm) and fast response (170 ms) were successfully achieved.