Anisotropic particle motion in optical landscapes modeled via the T-matrix optical scattering approach

Abstract

ABSTRACT Optical manipulation of nano- and micro-scale particles via optical tweezers and optical landscapes continuesto be of great interest in several “elds, re”ected by the myriad experimental pursuits suggesting selective andparallel control over particles of anisotropic shape (blood cells, nanorods, etc.). Our work here approaches thegoal of a complete model of these phenomena by means of optical scattering principles and, speci“cally, the T -matrix method. Here we describe the salient features of our model, which tends toward a complete and consistentmodeling scheme for determining the behavior of dielectric, polarizable, mesoscale particles of anisotropic shapein arbitrary intensity gradients. We explore forces and torques caused by periodic optical landscapes as well astorques induced by the polarization orientation of the electric “eld.Keywords: Optical Trapping, Optical Landscapes, T-Matrix Method, Optical Scattering 1. INTRODUCTION Trapping and manipulation of nano- and micro-scale particles within a micro”uidic environment continues tobe of great interest to several scienti“c communities. For example, the “eld of micro”uidic lab-on-a-chip wouldbe greatly enhanced by having access to accurate and ecient mechanisms for sorting chemical and biologicalcolloids. Broadly, there are two techniques for colloidal separation: extrinsic, requiring external identi“cation ofparticles (e.g., FACS), and intrinsic, in which properties inherent to the particles themselves (e.g., size, refractiveindex) are exploited. Extrinsic methods can add time and cost to the design of new assays in addition to beinginvasive to the particles themselves. Leading the charge toward intrinsic-based techniques are dielectrophoretic(DEP)