This letter presents resonant microelectromechanical systems capable of resolving subatomic features and/or measurement of atomic level forces in liquid media (in addition to air/vacuum). It has previously been shown that forces in the micro-and nano-Newton range applied to flexible extensionalmode resonant microstructures can cause significant resonant frequency shifts [1]. In this letter, the same principle has been applied to rotational mode disk resonators that are capable of maintaining relatively high quality factors in liquid. Preliminary results indicate about tenfold improvement in combined displacement-force resolution figure-of-merit compared with typical piezoresistive cantilevers when operating in liquid. Using integrated comb-drive electrostatic actuators, displacement and force resolutions as high as 200 fm and 1 nN, respectively, have been demonstrated. By application of the force through a levering mechanism, force sensitivities in the pN range can be achieved while maintaining sub-nm spatial resolution.Index Terms-MEMS resonant force-displacement sensor, in-liquid measurements, atomic force microscopy.

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.