Self assembly of microparticles in stable ring structures in an optical trap

Abstract

Micro-particle self assembly under the influence of optical forces produced by higher order optical beams or by projection of a hologram into the trapping volume is well known. In this paper, we report the spontaneous formation of a ring of identical microspheres (each with diameter 1.1 $\mu$m) in conventional single beam optical tweezers with a usual TEM${}_{00}$ Gaussian beam coupled into a sample chamber having standing wave geometry with a cover slip and glass slide. The effects of different experimental parameters on the ring formation are studied extensively. The experimental observations are backed by theoretical simulations based on a plane wave decomposition of the forward and backward propagating Gaussian beams. The ring patterns are shown to be caused due to geomterical aberrations produced by focusing the Gaussian beam using a high numerical aperture microscope objective into stratified media. It is found that the thickness of the stratified media and the standing wave geometry itself play a critical role in formation of stable ring structures. These structures could be used in the study of optical binding, as well as biological interactions between cells in an optical trap.

21 pages, 14 figures

References in corpus (1)

• Force unfolding kinetics of RNA using optical tweezers. I. Effects of experimental variables on measured results

Cited by in corpus (3)

• Controlled transportation of mesoscopic particles by enhanced spin orbit interaction of light in an optical trap
• Manipulating the transverse spin angular momentum and Belinfante momentum of spin-polarized light by a tilted stratified medium in optical tweezers
• Observation of Larmor-like precession of a single birefringent particle due to spin-dependent forces in tilted optical tweezers