TORSIONAL SPRING CONSTANT OBTAINED FOR AN ATOMIC FORCE MICROSCOPE CANTILEVER

Abstract

In this letter, a method to measure the torsional spring constant of a microcantilever is described. The cantilever was twisted laterally without any normal load by inducing the Lorentz force. An electrical current was applied to the cantilever in a magnetic field, and the torsional resonance frequency of the cantilever was obtained. Based on the observation that the torsional resonance frequency is the same as the second resonance peak of the thermally vibrating cantilever, the ratio of deflection spring constant to torsional spring constant is easily obtained from a simple relationship. For the cantilever used here, the torsional spring constant is 11.24 N/m, 28 times greater than the deflection spring constant. (C) 2004 American Institute of Physics.