Control over phase separation and nucleation using a laser-tweezing potential


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 poorly understood practice. Although there are now numerous examples of control using laser-induced nucleation, the absence of physical understanding is preventing progress. Here we show that the proximity of a liquid–liquid critical point or the corresponding binodal line can be used by a laser-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 a liquid mixture using a low-power laser diode confirm the effect. Phase separation and nucleation using a laser-tweezing potential explains the physics behind non-photochemical laser-induced nucleation and suggests new ways of manipulating matter.

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Fig. 1: Summary of the LIPS and laser-induced nucleation experiments.
Fig. 2: Experimental LIPS through the tweezing effect.
Fig. 3: Laser-induced nucleation triggered via the LIPS effect.


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We thank the Engineering and Physical Sciences Research Council (EPSRC) for support through grants EP/J004790/1, EP/J009733/1 and EP/N007417/1. We gratefully acknowledge discussions in 2010 with C. Bain that planted the seed for this work.

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The experiments and data analysis were conducted by F.W. Theory and simulations were conducted by K.W. Both authors contributed to writing the paper. K.W. conceived the overall project.

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Correspondence to Klaas Wynne.

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Supplementary Figs. 1–6, Supplementary Results

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Walton, F., Wynne, K. Control over phase separation and nucleation using a laser-tweezing potential. Nature Chem 10, 506–510 (2018).

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