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Proceedings Paper

Colloidal dynamics in the circularly symmetric optical potential of a Bessel beam
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Paper Abstract

In the optical domain, the gradient force may be exploited in optical tweezers to confine high-index particles to points of maximum light intensity [1]. This methodology has enabled key advances in biology enabling a deeper understanding of molecular motors and the properties of DNA. Optical traps have also enabled a wide range of studies in optical angular momentum, colloid science and microfluidics. Recent work has shown that extended, optically tailored landscapes can offer a mechanism by which to arrange and accumulate microparticles in pre-described arrays [2]). The ability to sculpt and reconfigure the optical potential energy landscape external to the sample is a key component of such studies. We may add a tilt to the potential or, more generally, break symmetry, enabling unprecedented control over directed transport of particles [3] Three dimensional optical lattices may be used for sorting and fractionation of biological material in a microfluidic flow [4]. However it would be advantageous to be able to separate and even accumulate both biological and colloidal matter in the absence of any flow within any sample chamber. This would allow true compatibility of sorting and separation without the need to implement flows and microfluidic systems. We exploit the varying affinity of mesoscopic objects to a circularly symmetric optical landscape to demonstrate this effect and demonstrate separation of cells and chromosomes. The differing Kramers residence time in each part of the light pattern leads to a thermally activated method for sorting based on their hopping probabilities within the rings of the Bessel beam. Whilst we employ a Bessel beam to elucidate and demonstrate the dynamics of the sorting other tailored landscapes can also be used.

Paper Details

Date Published: 27 August 2005
PDF: 11 pages
Proc. SPIE 5930, Optical Trapping and Optical Micromanipulation II, 59301L (27 August 2005); doi: 10.1117/12.614416
Show Author Affiliations
G. Milne, Univ. of St. Andrews (United Kingdom)
D. McGloin, Univ. of St. Andrews (United Kingdom)
K. Dholakia, Univ. of St. Andrews (United Kingdom)

Published in SPIE Proceedings Vol. 5930:
Optical Trapping and Optical Micromanipulation II
Kishan Dholakia; Gabriel C. Spalding, Editor(s)

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