Silicone Oil Grafting Optimization for Robust Low Hysteresis Water Repellent Surfaces

Hydrophobic low adhesion surfaces have gained increasing attention due to their excellent self-cleaning and water repellent properties which find applications in many engineering and industrial fields. Several methods to create hydrophobic surfaces which include grafting silicone oil on solid substrates have been reported in literature. Grafting of silicone oil creates polydimethylsiloxane (PDMS) brushes attached to the original solid surface, in our case smooth silicon but other substrates such as copper, aluminium and glass could also be adopted. The surface wettability and adhesion can then be tuned by various parameters such as viscosity, volume and/or number of layers, and temperature of the grafted oil. These surfaces created using the optimized parameters exhibit favourable results in terms of wettability with high contact angles (up to 109^o) and low contact hysteresis (below 1^o) which is comparable to Slippery Omniphobic Covalently Attached Liquid (SOCAL) surfaces or Slippery Lubricant Infused Porous Surfaces (SLIPS). Furthermore, mechanical and chemical stability tests demonstrate the robustness of the grafted coating. These findings provide a basic framework to select appropriate parameters for fabricating low hysteresis hydrophobic surfaces by silicone oil grafting.