Roof tile-shaped modes in quasi free-free supported piezoelectric microplate resonators in high viscous fluids

Abstract

This paper reports on higher orders of the roof tile-shaped bending mode in piezoelectrically actuated MEMS plate-type resonators with quasi free-free support, achieving an increased piezoelectric responseof ∼25% compared to a one-sided clamped cantilever structure with the same geometry and similarquality factor. Aluminum nitride (AlN) is used for the excitation of the devices offering different anchordesigns. These MEMS resonators are characterised by electrical and optical measurements in air and inseveral liquids (i.e., isopropanol and viscosity standards: D5, N10, N35, N100, D500). Nodal analyses arepresented and compared to both Finite Element Methods simulations and Laser Doppler Vibrometer mea-surements, demonstrating an excellent agreement between the positions of the plate supports with thoseof the nodal lines of the specific mode, which ensures a quasi free-free vibration. An optimized electrodedesign (OED) is established and compared to non-optimized actuation, showing superior performancefor plates with OED. The evaluation of the quality factor Q and the strain related conductance peak Gof the investigated modes results in the highest value for the 4th order mode (Q ∼ 100; G = 0.35 mS).Finally the piezoelectric response G/Q (∼4 S for 4th order mode) is presented, showing great potentialfor a large variety of challenging resonator based physical and chemical sensing applications.