CROSS TALK BETWEEN BENDING, TWISTING, AND BUCKLING MODES OF THREE TYPES OF MICROCANTILEVER SENSORS

Abstract

Microcantilevers generally deflect in three ways: bending, twisting, and buckling. Among these, the accurate measurement of bending is essential for atomic force microscopy imaging and sensing applications. However, it was found that the bending of certain cantilevers can be coupled with twisting and buckling of the cantilever. In this article, cross talk between bending and twisting modes of microcantilevers of three different designs such as rectangular, triangular, and piezoresistive cantilevers is described. For the experiments, a thermal stress was applied to the rectangular and triangular cantilevers, and a Lorentz force was exerted on the triangular and the piezoresistive cantilevers. While the bending of the rectangular cantilever induced a negligible amount of twisting when heated, the triangular cantilevers showed nonlinear twisting responses during bending. This nonlinear response of the triangular cantilever was attributed to the variations in the spring constants between the two legs. When a Lorentz force was exerted on the triangular cantilevers, coupling of the bending and twisting modes depended on the direction of a magnetic field. For the piezoresistive cantilevers, a Lorentz force induced the in-phase buckling which accompanied both the bending and twisting modes. (C) 2004 American Institute of Physics.