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

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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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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.

Author information


  1. School of Chemistry, WestCHEM, University of Glasgow, Glasgow, UK

    • Finlay Walton
    •  & Klaas Wynne


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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.

Competing interests

The authors declare no competing interests.

Corresponding author

Correspondence to Klaas Wynne.

Supplementary information

  1. Supplementary Information

    Supplementary Figs. 1–6, Supplementary Results