Research Projects

Colloidal crystals, made of micro- to nanoscale building blocks, have gained significant attention for their applications in photonic crystals, chemical sensors, photovoltaic, and antireflection surfaces. These structures can be fabricated using top-down or bottom-up approaches, with bottom-up approaches becoming more practical due to their cost and time-efficiency. However, the lack of active control over the morphology of the final pattern, particularly in 3D structures, remains a challenge. Optically-actuated patterning of particles from evaporating colloidal droplets is a potential solution to this issue. While these methods have shown success in fabricating unary and binary crystals, their applicability for higher-order crystals remains largely unexplored. This CRG proposal addresses two important issues: patterning of multicomponent metallic nanoparticles and patterning of non-absorbing particles. The core idea is to generate a temperature gradient along the surface of an evaporating droplet using light, causing a gradient in surface tension at the liquid surface. This leads to a surface-tension gradient driven flow, controlled by light, which could redistribute particle deposition inside the liquid drop. The project will involve large area patterning by scanning the laser beam along the liquid film, and characterizations using particle streak velocimetry, flow simulations, 3D analysis, SEM, and Voronoi analysis. The outcomes from this CRG project will significantly impact the development of multifunctional structures based on evaporative lithography.