Self-exciting and self-sensing resonant cantilever sensors for improved monitoring of airborne nanoparticles exposure

Self-exciting and self-sensing resonant cantilever sensors for airborne nanoparticles (NPs) monitoring are investigated. A fabricated self-sensing piezoresistive cantilever sensor is actuated using a piezo stack and operated in the second resonant mode. It is able to detect a resonant frequency shift of 33.58 Hz that corresponds to an airborne carbon NPs mass of 1.03 ng deposited during a 15-min sampling. The quality factor is 2100 resulting in a mass resolution of the sensor of 9.8 pg. In order to realize a portable airborne NPs monitoring device, thermally excited silicon cantilevers vibrating in different modes are proposed. The integration designs of heating resistors, sensing piezoresistors and electrostatic NPs sampling are further analyzed using finite-element modeling (FEM). An electrode for electrostatic NPs sampling is placed on the free-end of the cantilever. The results indicate that a self-sensing silicon electrothermal cantilever can fulfill the requirements of portable monitoring of airborne NPs exposure.