Development of a superhydrophobic/ superhydrophilic hybrid surface by selective micropatterning and electron beam irradiation

Recent advances in micro/nano-technology have driven artificial modifications of surface wettability by mimicking biological surfaces, such as superhydrophobic and water harvesting surfaces. In this study, surface wettability of polycarbonate (PC) films was modified using various surface treatments: Micropatterning using ultrasonic imprint lithography, hydrophobic silane coating, and electron beam irradiation. To modify surface wettability selectively in a specified region, these three treatments were performed using '#'-shaped masks with positive and negative shapes. Various combinations of these treatments were investigated in terms of wettability changes, by measuring contact angle (CA). The semi-hydrophobic PC film (CA: 89.2°) was modified to create a superhydrophobic state (CA: 155.9°) by virtue of the selective micropatterning and coating. The electron beam irradiation had an opposite effect, reducing the CA (48.2°), so the irradiated region was modified to a hydrophilic state. Two combinations of the proposed surface modifications made it possible to obtain considerable difference in CA on a single surface (107.7°), and to obtain four different wetting states on a single surface. Water-drop experiments showed that the developed hybrid surfaces were selectively wettable and showed water collection capability.