University of Cambridge > > Institute for Energy and Environmental Flows (IEEF) > Patterning of Colloidal Particles via Infrared Radiation-Assisted Evaporative Lithography

Patterning of Colloidal Particles via Infrared Radiation-Assisted Evaporative Lithography

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Colloidal particles in a volatile fluid can be driven laterally by a non-uniformity of the evaporation rate. In the process called evaporative lithography, the evaporation rate is modulated by holding a mask close to the fluid surface. The particles are carried with the water flow to the fast evaporating regions under the open regions in the mask. Thus, periodic patterns of particles can be created on a surface. We have extended evaporative lithography by directing infrared radiation through a mask onto concentrated dispersions of polymer particles. Radiative heating increases the evaporation rate locally under the open regions of the mask, leading to pattern formation. Furthermore, the polymer particles are heated above its glass transition temperature and sinter into a coherent textured coating. We have found that the height of the coating’s topography increases with an increase in several key parameters: the initial thickness of the film, the volume fraction of particles, and the pitch of the pattern. The results are interpreted by using models of geometry and particle transport. The patterned coatings can function as “paintable” microlens arrays, applicable to nearly any surface. Compared with existing methods for creating textured coatings, IRAEL is simpler, inexpensive, able to create a wide variety of bespoke surfaces, and applicable to nearly any substrate without prior preparation.

This talk is part of the Institute for Energy and Environmental Flows (IEEF) series.

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