A guide to soft colloidal lithography: Advances in microgels at fluid interfaces, preparation methods and applications of 2D microgel monolayers

Abstract

Nanostructured surfaces have gained significant attention over recent decades due to their diverse technological applications across multiple fields. The fabrication of artificial nanostructures typically relies on lithographic approaches, yet conventional lithography techniques face challenges related to scalability and high costs, prompting the emergence of soft colloidal lithography (SCL) as a promising alternative for designing large-scale crystalline nanostructures. SCL exploits the rapid and large scale self-assembly of microgels at fluid interfaces and their subsequent transfer to solid substrates. Despite its potential, SCL remains underused in most clean room facilities, hindering its implementation in industrial processes. This review addresses this gap by providing both soft matter and materials science communities with tools to effectively design SCL-based materials. We start presenting an updated overview of microgel behavior at fluid interfaces, which is the platform providing the better tools to tune the final monolayer pattern. We then present a comprehensive guidance on preparation procedures, encompassing both direct assembly methods and interface-assisted approaches. Finally, we review applications of SCL-fabricated materials, including those where deposited microgels serve as functional elements and those where monolayers function as either positive masks for nanowire fabrication or negative masks for nanohole production. Throughout the review, we identify promising research directions to advance the SCL technique and propose applications where this methodology could enhance existing technologies.