Electromagnetic wave technique to determine radiation torque on micromachines driven by light

A method to determine radiation torque on a dielectric microrotor driven by a focused laser beam, while considering the wave nature of the incident light, is introduced. The method involves numerically determining the electric and magnetic field quantities of the scattered light on the surface of the rotor using the finite difference time domain method. Maxwell's stress tensor is then employed to calculate the force over the rotor surface, enabling the determination of the rotor torque about the axis of rotation. The method is demonstrated using a simple rotor shape, with results that are in good qualitative agreement with observations reported in literature. (C) 2003 American Institute of Physics.