Capillary-Induced Clustering of Thermoresponsive Micropillars

Effectiveness of organic solvents for recovering collapsed PDMS micropillar arrays

Polydimethylsiloxane (PDMS) micropillar arrays are widely used in research labs and engineering fields as analytical tools for various purposes. When the micropillar length or density surpasses a critical value, micropillars tend to collapse with each other and become unusable. Restoring collapsed PDMS micropillars typically involves the use of low surface tension solvents and ultrasound sonication, but such approach has received little success to date. In this work, we examined the effectiveness of different types of solvents for restoring collapsed PDMS micropillar arrays and show that the swelling ratio of PDMS in selected solvents constitutes an important factor in the effectiveness of restoring collapsed PDMS micropillars. Our results could be a promoter in recycling PDMS micropillar arrays and achieving economic and social benefits.

Robust and Transparent Lossless Directional Omniphobic Ultra-Thin Sticker-Type Film with Re-entrant Micro-Stripe Arrays

Directional droplet-sliding control without wetting the surface is immensely required in advanced surface engineering, including biological and chemical analyses or green technology. However, the development of robust and transparent thin sticker-type directional omniphobic films for portable usage in smart microfluidic platforms is rare. In this study, we report a novel perfluoropolyether (PFPE) directional omniphobic film (PDOF). The PDOF is a robust and transparent ultra-thin sticker-type film that can control the anisotropic sliding of various liquid droplets on the surface. The PFPE is a chemically stable and turgid material compared to polydimethylsiloxane (PDMS), which is often used to fabricate liquid-repellent thin films. A well-designed fabrication criterion through adhesion engineering in the soft-molding process was developed using the PFPE to obtain a PDOF with a thickness of 56 μm, with re-entrant micro-stripe structures on the surface. The fabricated PDOF showed intriguing liquid sliding properties based on the direction and spacing of the microstructures. This aspect is defined as an anisotropic factor.