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Proceedings Paper

Control over phase separation and nucleation using a optical-tweezing potential
Author(s): Klaas Wynne; Finlay Walton
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Paper Abstract

Control over the nucleation of new phases is highly desirable but elusive. Even though there is a long history of crystallization engineering by varying physicochemical parameters, controlling which polymorph crystallizes or whether a molecule crystallizes or forms an amorphous precipitate is still a black art. Although there are now numerous examples of control using laser-induced nucleation, a physical understanding is absent and preventing progress. We will show that concentration fluctuations in the neighborhood of a liquid-liquid critical point can be harnessed by an optical-tweezing potential to induce concentration gradients. A simple theoretical model shows that the stored electromagnetic energy of the laser beam produces a free-energy potential that forces phase separation or triggers the nucleation of a new phase. Experiments in liquid mixtures using a low-power laser diode confirm the effect. Phase separation and nucleation through an optical-tweezing potential explains the physics behind non-photochemical laser-induced nucleation and suggests new ways of manipulating matter.

Paper Details

Date Published: 7 September 2018
PDF: 6 pages
Proc. SPIE 10723, Optical Trapping and Optical Micromanipulation XV, 107230O (7 September 2018); doi: 10.1117/12.2324119
Show Author Affiliations
Klaas Wynne, Univ. of Glasgow (United Kingdom)
Finlay Walton, Univ. of Glasgow (United Kingdom)

Published in SPIE Proceedings Vol. 10723:
Optical Trapping and Optical Micromanipulation XV
Kishan Dholakia; Gabriel C. Spalding, Editor(s)

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