Rainbows in a bottle: Realizing microoptic effects by polymerizable multiple emulsion particle design

These iridescent structural colours are of immense significance2 but not easy to control experimentally and therefore difficult to exploit for applications. In this work, we employ microfluidics to produce polymerizable double emulsions that can not only induce the already known lensing effect3 but also result in the spectral separation of white light.

Here, liquids of varying refractive in-dex that constitute the emulsions resulted in patterns of iridescent colours. After polymerization, the inner emulsion cores collapse and this results in curved concave surfaces on these polymeric microspheres. Interestingly, the light propagation along the curved surfaces undergo total internal reflection, followed by near-field interference along exit structures on the polymerized microspheres4.