Mechanically durable, super-repellent 3D printed microcell/nanoparticle surfaces

Three-dimensional (3D) printed re-entrant micropillars have demonstrated high static contact angles for an unprecedented variety of liquids, but have yet to achieve this with low contact angle hysteresis and excellent abrasion resistance. We report on the demonstration of 3D printed microcell/nanoparticle structures that exhibit high static contact angle, low contact angle hysteresis, and high mechanical durability. Micropillars and microcells both exhibit high static contact angles with water and ethylene glycol (EG), but suffer from high contact angle hysteresis, indicative of rose petal wetting. Our modeling results indicate that micropillars are able to achieve higher static contact angle and breakthrough pressure simultaneously compared with microcells. However, simulations also indicate that micropillars have higher maximum equivalent stress at their bases, so that they are more prone to mechanical failure. We address contact angle hysteresis and mechanical durability issues by the creation of 3D printed microcell/nanoparticle arrays that demonstrate super-repellency and retain their super-repellency after 100 cycles of mechanical abrasion with a Scotch-Brite abrasive pad under a pressure of 1.2 kPa. The use of interconnected microcell structures as opposed to micropillars addresses mechanical durability issues. Low contact angle hysteresis is realized by coating 3D printed structures with low surface energy nanoparticles, which lowers the solid–liquid contact area fraction. Our results demonstrate new 3D printed structures with mechanical durability and super-repellency through the use of microcell structures integrated with fluorinated nanoparticles.