Fabrication of polymer-based water-repellent surfaces of complex shapes by physical transfer of nanostructures

This work reports large-area fabrication of polymer [polydimethylsiloxane (PDMS), polycaprolactone (PCL) and polytetrafluoroethylene (PTFE)]-based superhydrophobic surfaces decorated with Cu(OH)2 nanowires. The process flow involves fabrication of nanostructured copper hydroxide surface (Cu(OH)2_NSS) by etching and coating the Cu(OH)2_NSS with a hydrophobic silane layer. This is followed by transferring the nanowires on to the polymer surface. The fabricated surfaces [which are Cu(OH)2 nanowires on PDMS: PDMS_Cu(OH)2, Cu(OH)2 nanowires on PCL: PCL_Cu(OH)2 and Cu(OH)2 nanowires on PTFE: PTFE_Cu(OH)2] exhibited dual scale roughness imparting very good water repelling behavior with a static contact angle greater than 150° and contact angle hysteresis of less than 10°. In addition to water repelling behavior, the fabricated surfaces exhibited bloodphobic behavior making them suitable for specific healthcare applications. Using the same technique, fabrication of superhydrophobic surface with complex 3D shape was also demonstrated. The same methodology was further adopted to fabricate a large-area (22 cm × 22 cm) superhydrophobic surface by replacing silane with stearic acid, which is a non-fluorinated surface modifying agent. This helped in reducing the cost and time of fabrication which is important when it comes to large-scale manufacturing.