We have used wettability patterning to create an open-surface heat exchanger that provides efficient cooling by using less amount of coolant directed from an impinging jet only to the areas that require protection from overheating. Heat removal rates of the order of 100 W/sq. cm are attained without phase change at water flow rates as low as 1 mL/s and chip superheats of 65 C. The approach opens up new opportunities for heat-removing devices that rely on advective cooling with wettability-patterned metal substrates.

We have developed environmentally-friendly, water-repellent coatings consisting of 99.5% naturally-occurring materials, with the remaining 0.5% comprising an FDA-approved cross-polymer. These coatings offer an exciting technological advancement in water-repellency with materials that pose no threat to the environment.

We have used liquid-cell transmission electron microscopy to observe nanoparticle interactions in a liquid environment. In this real-time video, gypsum nanoparticles are seen as they collide and aggregate in water to form large aggregates and needle-shaped particles.

Liquid jet impact on flat, impermeable substrates is important for many applications ranging from electronic equipment cooling, to fuel atomization, and erosion of solid surfaces. On a wettable surface, the jet can form a hydraulic jump. On a superhydrophobic surface, the liquid breaks up into droplets ejected outward. We have developed a simple, scalable, wettability-patterning approach for delaying or even eliminating droplet breakup in the case of jet impingement on horizontal superhydrophobic surfaces.

Liquid-jet impingement on a porous material is particularly important in many applications of heat transfer, filtration, or in incontinence products. Generally, it is desired that the liquid not penetrate the substrate at or near the point of jet impact, but rather be distributed over a wider area before reaching the back side. We have developed a wettability-patterning technique that causes a uniform distribution of the liquid on porous substrates of 50 sq cm area, with minimal or no spilling over the sample edges at jet flow rates exceeding 1 L/min.

We have designed and fabricated a self-driven flat-surface micromixer that features multiple wedge tracks and promotes mixing of small liquid volumes (μL droplets). Planar, non-wettable “islands” of different shapes act as obstacles, further augmenting the mixing. The method brings us closer to low-cost surface microfluidic mixing devices.

We demonstrate how the spontaneous spreading behavior of aqueous droplets on wettability-patterned diverging tracks is affected by the viscosity of the fluid.

Professor Megaridis delivers a lecture on his career path. The presentation was made on 3/18/2019 in Chicago; it was the inaugural lecture in a new TED-style talk series intended to document career and life reflections of newly-appointed Engineering Distinguished Professors at UIC.

UIC students perform experiments in reduced gravity. Dr. Megaridis was the faculty advisor.