Direct Piezoresistive Self-Sensing of Electromechanical Motion in Suspended Nanostructures

Efficient electrical transduction of nanoscale motion is a key aspect of having ON-chip realization of nanoelectromechanical systems (NEMS). The traditional amplitude modulation (AM) schemes used for the purpose have complex circuit configurations, leading to challenging control over circuit parameters. In this article, a facile method to transduce electromechanical motion in suspended nanostructures using their intrinsic piezoresistivity is demonstrated. The $1\omega $ AM method, largely used for graphene nanomechanical resonators through capacitive coupling with the gate, is not very effective for materials with lower conductivity and also for low-dimensional structures. Moreover, in the present work, it is shown that the aforementioned method is not purely capacitive but rather a combination of linear capacitive and piezoresistive components. A purely piezoresistive method, however, can address the transduction of a wide range of materials and nanostructures. In this effort, a piezoresistive transduction method is formulated that involves simple circuitry and has a nonscaling electrical background independent of the mechanical motion, unlike the $1\omega $ transduction scheme. This facilitates an easy discernment of the electromechanical resonance for different drive voltages. Experimental measurements performed on an in-house fabricated reduced graphene oxide (rGO)-based suspended piezoresistive membrane reliably support the formulation of the principle of piezoresistive transduction advanced in this article.