Long-term Repellency of Various Liquids by Interconnected Reentrant Structures

A nano-micro structure can be produced on a substrate using nano imprint lithography. Interconnected reentrant structure can be manufactured through an additional process using capillary wrapping on this structure, and an omni-phobic surface having both hydrophobic and oleophobic properties can be implemented using the regularly arranged interconnected reentrant structure.<br/>During the process, the material used to manufacture the initial microstructure and the material used in additional processes may be different, which affects the geometric properties of the reentrant structure. For example, if the material used to manufacture microstructures is the same as the material used in additional processes, capillary force will occur smoothly due to chemical affinity and structural stability will also be excellent. If the two materials are different, capillary force phenomena will occur differently depending on the surface properties of the material. As such, the strength of capillary force will all vary depending on the material used in the process, so if it is used well, the geometric shape of the structure to be finally produced can be controlled.<br/>To examine the liquid repellency of the Reentrant structure manufactured by the process, a contact angle is measured using various liquids (artificial saliva, hexane, oil, etc.) and DI water. The liquid repellency properties will vary due to surface tension, viscosity, evaporation, and other chemical compositions depending on the liquid. In addition, when various liquids are in contact for a long time, the wetting tendency according to the liquid will be different.<br/>In this study, using various polyurethane acrylate(PUA) ultraviolet(UV) curable resins, the capillary force lithography process was conducted to manufacture the interconnected-reentrant structure. Thereafter, in order to analyze the repellency properties of the surface, the behavior according to contact time for various liquids and the contact angle was observed.<br/><br/><br/><br/><b>Acknowledgment </b><br/>This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT) (No. 2019R1A5A8083201).