Simulation and Measurement of the Time-Varying Casimir Force

John Kohoutek, Ivy Yoke Leng Wan, Hooman Mohseni

Bio-Inspired Sensors and Optoelectronics Laboratory (BISOL), EECS, Northwestern University

Abstract

In this talk we will present a new method for verification of the Casimir force with an Atomic Force Microscope (AFM) in tapping mode. Also being presented will be a theoretical model based on the harmonic oscillator and shown in Mathematica. With this method, originally based on the phase of vibration of the AFM tip, we are able to verify the Casimir force at distances of nearly 7 nm with an AFM tip that has a radius of curvature of nearly 100 nm. The theoretical model accurately predicts both the amplitude versus distance and phase versus time curves given by the AFM. Indeed, because this measurement is done in tapping mode, it is a dynamic measurement, as oppose to other Casimir force measurements. Therefore, the model can also give us plots of the Casimir and electrostatic forces as a function of time. We find that with a potential difference of 0.625 V between the tip and surface, the Casimir force is actually over four times stronger than the electrostatic force when the tip is at the minimum distance to the surface. We believe that these findings underscore the importance of the Casimir force not only in tapping mode AFM but in all nanoscale devices.