Optimization of optically-driven micromachines

While a variety of different optically-driven micromachines have been demonstrated by a number of groups around the world, there is a striking similarity in the designs used. The typical optically-driven rotor consists of a number of arms attached to a central hub, or elongated stalk in the case of free-floating rotors. This is a consequence of the relationship between the symmetry of a scattering object and the transfer of optical angular momentum from a beam to the object. We use a hybrid discrete-dipole approximation/T-matrix method algorithm to computationally model the scattering by such optically-driven rotors. We systematically explore the effects of the most important parameters of rotors, such as the thickness, length, and width of the arms, in order to maximize the torque efficiency. We show that it is possible to use computational modelling to optimize the design of such devices. We also compare the computational results with experiment