Torsional Tip Motion of Double Beam Atomic Force Microscopy
This paper investigates the vibration of a coupled microcantilever beam structure, in which a rigid body at their free end connects the two beams. The coupled beams are under equal and out-of-phase forces applied by piezoelectric films, which result in overall torsional motion. The equations describing the motion of the structure as well as the boundary conditions are developed using the Hamilton principle under the assumption of the structure being an Euler-Bernoulli beam. Two equations for each beam are realized: bending and torsional equations, which are combined in one torsional equation. The equation is solved using Galerkin approximation. The effects of dimensional parameters and input parameters are investigated including height, width, thickness, beam arrangement, applied voltage, input frequency, and mass of the tip. Geometry and mass were found to have significant effects on the angle, while input voltage was found to have a small linear effect. The overall sweeping motion was found to have an angle well below one degree in general. This shows that while the piezoelectric actuators can generate torsional sweeping, the effect is at a small angle that depends more on design than actuation force.