Facile Lithographic Fabrication of Closed-Loop Reentrant Micromesh via Shape Memory Effect-Induced Suspension for Robust Liquid-Repellency

Imprint lithography is one of the most used techniques for fabricating microstructures, owing to its high efficiency in both costs and time. However, imprinting has limited feasibility in realizing complex microstructures due to difficulties arising from the inherent limitations in the demolding process. Herein, a facile method is demonstrated for fabricating closed-loop reentrant topographies with microscale meshes through a combination of imprint lithography and shape memory polymer (SMP). The mesh structure imprinted onto the pre-pressed SMP pillar array can be elevated by utilizing the form-switchable property of SMP to fabricate suspended micromesh. Suspended micromesh is fully supported by restored SMP micropillar array, exhibiting a closed-loop shape that cannot be achieved with conventional imprint lithographic methods. Also, by the nature of reentrant geometry, liquid-repellency can be realized even for liquids with a lower surface tension than water, offering numerous applications in self-cleaning, droplet manipulation, and antifouling. Various liquid-repellent performances of the fabricated suspended micromesh are investigated and compared to the theoretical expectations for a non-wetting structure, confirming the successful establishment of reentrant topography in the fabricated structures. The proposed lithographic technique can be broadly utilized not only for liquid-repellent surfaces but also for the fabrication of various functional structures.