Optimization of optically-driven micromachines

Abstract

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.

On the electromagnetic scattering of arbitrary shaped beams by arbitrary shaped particles: A review

“…Capabilities and known limitations of a DDA-code, named ADDA, are described by Yurkin and Hoekstra [216]. See also below [217] for DDA.…”

“…A T-matrix pointmatching method was also used in an optical tweezers computational toolbox available from Nieminen et al [189]. See also Nieminen et al for a very comprehensive review on the physics of optical tweezers [220], Nieminen et al [221] for application to the study of forces in optical tweezers with radially and azimuthally polarized trapping beams, Loke et al [217] for a hybrid method for evaluating T-matrices in which point-matching is used in conjunction with the discrete-dipole approximation (DDA), and Nieminen et al [24] for a review. The same approach was used by Bareil and Sheng [222] to study both the angular and position stability of a nanorod trapped in optical tweezers, and also by the same authors [223] for modeling a highly focused laser beam in optical tweezers.…”