Harnessing colloidal microchannel formation for low-cost large-scale micropattern manufacturing

Crack formation in drying colloidal films is critical in a wide range of applications coatings, electronics, and advanced manufacturing. While cracks are often regarded as defects, they can also be harnessed as a powerful route to constructing large scale uniform patterns at extremely low cost. During solvent evaporation, capillary stresses and the well-known "coffee-ring effect" drive the adaptive organization of colloidal particles, giving rise to ordered and interconnected microchannels. Remarkably, such processes are robust, energy-efficient, and capable of producing large-area, well-defined structures without the need for complex instrumentation. In this review, we highlight recent progress in understanding and exploiting cracks in drying colloidal films, with the aim of fully leveraging their advantages both in fundamental studies and practical applications. We begin by summarizing the fundamental principles governing drying-induced pattern formation, from particle transport in the coffee-ring effect to capillary-driven crack propagation. We then discuss strategies to regulate and control the generation of parallel and highly ordered crack arrays. Finally, we survey emerging applications of colloidal microchannels in diverse fields, including flexible transparent electrodes, electronic devices, and solar cells. By integrating fundamental mechanisms with application-oriented design, this review establishes cracks in colloidal films not merely as an unavoidable by-product of drying, but as a versatile platform for scalable self-assembly and functional material fabrication.