Sequential Dissolution Demolding for the Replication of Multifunctional High-Aspect-Ratio Copper Micropillar Arrays.

Nanoimprint lithography (NIL) is widely used to pattern material surfaces for functional modification. To advance this capability, we develop a sequential dissolution demolding (SDD) technique based on selective material solubility, enabling two consecutive, stress-free demolding processes. This approach capitalizes on the differential solubility of positive photoresists, which withstand non-polar solvents but dissolve readily in alkaline aqueous solutions following UV exposure. Utilizing this mechanism, the high-aspect-ratio (HAR) micropillar arrays (aspect ratios up to 20:1) on photoresist masters were successfully replicated into lipophilic polystyrene (PS) films, yielding intermediate templates comprising deep microcavities. These cavities were subsequently metallized via an electroplating process. By dissolving the PS template in a non-polar solvent, high-quality, free-standing HAR copper (Cu) micropillars were isolated without inducing mechanical strain. Furthermore, these engineered Cu structures exhibited valuable multifunctional properties, including anti-reflective and antibacterial characteristics. This stress-free demolding strategy provides a robust pathway to broaden the applicability of NIL in complex nanofabrication.