Piezoelectric excited millimeter sized cantilever sensors for measuring gas density changes

Rapid, in-situ measurement of gas density is valuable for monitoring industrial processes. We show that piezoelectric-excited millimeter-sized cantilever (PEMC) sensors exhibit precision for measuring gas density changes as small as 0.088 g/l with sensitivity equivalent to 0.049 g/(l Hz). PEMC sensors were fabricated by bonding 127 μm thick piezoelectric layer (lead zirconate titanate) to a base 160 μm thick silica layer. Gases (He, N2, Ar) were passed continuously through an isothermally maintained flow cell, in which the PEMC sensors were mounted and the steady state resonant frequency values were monitored. The changes in observed resonant frequencies were collected and compared in multiple experiments with well-established theory for the frequency response of a dynamic cantilever surrounded by an inviscid fluid and were found to be in reasonable agreement. A finite element model of the PEMC sensor showed good agreement with the measured resonant frequency values.