Abstract
In order to address the challenges presented by future electronics with complex functionality and architecture, new materials and fabrication methods must be developed. In contrast to traditional top-down approaches, bottom-up self-assembly has emerged as a robust means of organizing nanoscopic building blocks into highly ordered structures and materials. In particular, topographical micropatterns are typically fabricated using complicated lithographic methods that are expensive and time-consuming and not suitable for high throughput manufacturing. Colloidal cracks, also known as colloidal microchannels, have been identified as a simple and robust strategy for the fabrication of scalable microchannels. Despite extensive theoretical modeling to understand the mechanism of crack formation, the influence of the “coffee-ring” effect on crack formation remains largely unexplored. Herein, we explore how the “coffee-ring” effect determines the colloidal microchannel formation by leveraging the kinetic control of the non-equilibrium deposition process of PS latex nanoparticles. Surprisingly, by tuning the particle size, we found the “coffeering” effect plays a dual role in determining the colloidal microchannel formation. In addition, temperature-concentration phase diagrams of colloidal microchannel formation are also provided in this work. Overall, the study presented offers crucial insights into controlling the self-assembly of colloidal particles to form microchannels, which is essential for the low-cost and large-scale fabrication of topographical templates. This study has important applications in microfluidics, geometry confinement for functional materials deposition, and alignment.