Resonant Mems for High Resolution Atomic Force and Displacement Measurements in Liquid

Abstract

This work presents resonant microstructures capable of resolving subatomic features and/or measurement of atomic level forces in liquid media. It has previously been shown that forces in the micro-and nano-Newton range applied to laterally flexible extensional-mode micro-resonators lead to significant resonant frequency shifts [1]. In this work a similar principle has been applied to rotational mode disk resonators capable of maintaining relatively high quality factors in liquid. Preliminary results indicate about 10-fold improvement in combined displacement-force resolution in liquid compared to typical piezoresistive cantilevers. Using integrated comb-drive electrostatic actuators, displacement and force resolutions as high as 200fm and 1nN have been demonstrated. Using softer resonant structures or application of the force through a levering mechanism, force sensitivities in the pN range can be achieved while maintaining sub-nm spatial resolution.