Designing Micro-Mechanical Cantilever Resonator Arrays for Wideband Detection of Ultrasonic Xylem Cavitation Emissions Related to Plant Water-Stress

Precision agriculture lacks automated noninvasive, low-power methods of in-field monitoring of early symptoms of water-stress on individual plants. Water-stress causes the occurrence of cavitation bubbles in xylem vessels of woody plants, producing ultrasonic emissions detectable on the plant’s trunk surface. We propose a MEMS design of a frequency-selective array of piezoelectric resonators, enabling low-power sorting of ultrasonic emissions by their frequency ranging from 100 to 500 kHz. Here we present an early design of such resonator array based on micro-cantilever beams with AlN thin-film piezoelectric electrodes. Finite element modeling was used to optimize beam geometries and piezoelectric electrode design, maximizing the piezoelectric voltage. A microfabrication technological process is proposed. Mechanical resonator arrays were prototyped on SOI wafers by front and back-side deep reactive ion etching (DRIE). Beam’s resonance modes were preliminarily measured by optical vibrometry.