Using GPUs for Realtime Prediction of Optical Forces on Microsphere Ensembles

Abstract

Laser beams can be used to create optical traps that can hold and transport small particles. Optical trapping has been used in a number of applications ranging from prototyping at the microscale to biological cell manipulation. Successfully using optical tweezers requires predicting optical forces on the particle being trapped and transported. Reasonably accurate theory and computational models exist for predicting optical forces on a single particle in the close vicinity of a Gaussian laser beam. However, in practice the workspace includes multiple particles that are manipulated using individual optical traps. It has been experimentally shown that the presence of a particle can cast a shadow on a nearby particle and hence affect the optical forces acting on it. Computing optical forces in the presence of shadows in realtime is not feasible on CPUs. In this paper, we introduce a raytracingbased application optimized for GPUs to calculate forces exerted by the laser beams on microparticle ensembles in an optical tweezers system. When evaluating the force exerted by a laser beam on 32 interacting particles, our GPUbased approach is able to get a 66fold speed up compared to a single core CPU implementation of traditional Ashkin's approach and a 10fold speedup over the single core CPUbased implementation of our approach.