Liquid-Loaded Piezo-Silicon Micro-Disc Oscillators for Pico-Scale Bio-Mass Sensing

Fully differential higher order transverse mode piezoelectric membrane resonators for enhanced liquid-phase quality factors

“…The highest liquid-phase measured among the membrane resonators tested was 270 (transverse (2, 0) mode), which is 70% higher than the lower order transverse (1, 0) mode transduced in the same membrane resonator. Although transverse flexural plate modes tend to suffer lower liquid-phase Q than contour modes [17][18][19], the liquid-phase Q reported here is comparable to contour mode resonators reported in the literature and higher than some [13][14][15][16]. By testing over a range of membrane sizes, we have observed that there exists an optimal membrane size that offers the highest Q and lowest R m in liquid-phase, a trend that deviates from measurements of the same devices in ambient pressure.…”

“…The reduction in the output resonant peak is further compounded for high dielectric constant fluids like water, which significantly increases the direct parasitic feedthrough between the input and output port of the MEMS resonator. Hence although capacitive MEMS resonators have been explored for liquid-phase sensing [10][11][12], thin-film piezoelectric MEMS resonators [13][14][15][16][17][18][19][20][21][22][23][24] have been receiving growing interest more recently as they offer superior electromechanical coupling efficiency than the former. The higher electromechanical coupling efficiency helps buffer the reduction in signal output typical of MEMS resonators electrically characterized in liquids and desirably lowers the motional resistance (R m ).…”

“…Given that the design of the piezoelectric MEMS resonator affects liquid-phase Q and R m , many different designs have been proposed to deliver higher liquid-phase Q and lower R m . Many of the resonator modes offering higher Q have tended to be contour mode type designs [13][14][15][16][17][18][19], where the displacements are primarily within the plane of the resonator to reduce fluidic damping. These modes are characterized by higher stiffness (in contrast to more compliant transverse bending modes) for higher energy storage capacity that helps increase liquid-phase Q.…”