Flexible and Stable Omniphobic Surfaces Based on Biomimetic Repulsive Air-Spring Structures

Abstract

In artificial biological circulation systems such as extracorporeal membrane oxygenation, surface wettability is a critical factor in blood clotting problems. Therefore, to prevent blood from clotting, omniphobic surfaces are required to repel both hydrophilic and oleophilic liquids and reduce surface friction. However, most omniphobic surfaces have been fabricated by combining chemical reagent coating and physical structures and/or using rigid materials such as silicon and metal. It is almost impossible for chemicals to be used in the omniphobic surface for biomedical devices due to durability and toxicity. Moreover, a flexible and stable omniphobic surface is difficult to be fabricated by using conventional rigid materials. This study demonstrates a flexible and stable omniphobic surface by mimicking the re-entrant structure of springtail’s skin. Our surface consists of a thin nanohole membrane on supporting microstructures. This structure traps air under the membrane, which can repel the liquid on the surface like a spring and increase the contact angle regardless of liquid type. By theoretical wetting model and simulation, we confirm that the omniphobic property is derived from air trapped in the structure. Also, our surface well maintains the omniphobicity under a highly pressurized condition. As a proof of our concept and one of the real-life applications, blood experiments are performed with our flat and curved surfaces and the results including contact angle, advancing/receding angles, and residuals show significant omniphobicity. We hope that our omniphobic surface has a significant impact on blood-contacting biomedical applications.

Diffusion-Based Separation of Extracellular Vesicles by Nanoporous Membrane Chip

“…The chip fabrication was based on previous work [ 62 ]. Briefly, the inlet chamber was made using a micro-mold of photoresist SU-8 2075 (Microchem, Westborough, MA, USA).…”

Omniphobic surfaces: state-of-the-art and future perspectives

“…However, utilizing various amount of functionalized PMMA with different fluorine content and also various aggregate Reproduced with permission from ref. [32].…”

“…The entrapped air pockets in micro-cavities could push the liquid droplets away and stabilize a reversible non-wetting Cassie state. In a similar study, Seo et al [32] fabricated a repulsive air-spring structure by mimicking the springtail's skin. The surface was consisted of a 500 nm hole arrayed flexible PDMS membrane and the micron-size pillar structures.…”

“…Figure 7. SEM images of casted DFHM-ef-PMMA film surface; and enlarged view (inset).Reproduced with permission from ref [32]…”

Tulip-Shaped Pattern Imprinting for Omni-Phobic Surfaces Using Partially Cured Photopolymer

“…This deformation increases the diameter of the upper end of the pattern, decreases the diameter and height of the lower end, and increases the surface roughness of the upper surface of the pattern. The deformed pattern has a tulip shape, and the hydrophobicity and oleophobicity of the surface are improved by the air pocket effects and increased roughness [17,19,27,[35][36][37][38][39][40][41]. In the final step, the process is completed by final curing using ultra high-power UV to improve the wear resistance and omni-phobicity of the tulip structure.…”