Effect of Surface Omniphobicity on Drying by Forced Convection (Briefing Charts)

Low energy surfaces can strongly repel both oil and water. Recently these surfaces have been fabricated on various substrates including fabric, aluminum, stainless steel and many other materials. In this experiment we explore the use of low energy surface deposition on aluminum alloy, stainless steel and silicon substrates, to enhance the drying rate of liquids removed from the surface by forced convection. We control surface roughness by substrate abrasion and by the growth of Al2O3 nanograss to enhance liquid repellence by use of a hierarchical texture. Liquid repellence of the substrates is measured by contact angles of the probe liquids, water and hexadecane. Samples are mounted on a rigid stage constructed with a flat surface and a regulated air nozzle fixed to provide flow parallel to the substrate surface. The velocities of probe liquid droplets placed on the substrates are recorded via high-speed camera as they are moved by a constant air flow. It is shown that drops on omniphobic and superomniphobic surfaces move at increased velocity compared to untreated surfaces, and leave behind less residual liquid, resulting in a faster drying rate. 2- factor design of experiments DOE was implemented to explore the optimum conditions for a fast drying low energy surface. The use of DOE and the results of this experiment are merged into a lesson plan developed for 9th-12th grade students. These results will serve as examples low energy surfaces and their potential applications.