Instant Tuning of Superhydrophilic to Robust Superhydrophobic and Self Cleaning Metallic Coating: Simple, Direct, One-Step and Scalable Technique.

We present a simple, direct, one-step, scalable technique for instant tuning of all the different states of wetting characteristics using atmospheric plasma spray (APS) technique. We observed that, just by changing the process parameters in APS technique, the wetting characteristics of an intrinsically hydrophilic aluminium metallic surface can be tuned to superhydrophilic (CA: 0°), hydrophilic (CA: 19.6°), hydrophobic (CA: 97.6°) and superhydrophobic (CA: 156.5°) surfaces. Also, tuned superhydrophobic surface showed an excellent self-cleaning property. Further, we demonstrated that these surfaces retain their superhydrophobic nature even after exposure at elevated temperatures (upto 773 K) and on application of mechanical abrasion. Manipulation in different wetting behaviour was possible mainly due to the presence of varying degree of smooth surface as well as micro-pillars, which incorporated the multi-scale roughness to the surface. "Re-entrant" like microstructures such as mushroom, cauliflower and cornet microstructures was observed in the case of tuned superhydrophobic surface, which is well known for achieving the excellent water repellency over the hydrophilic surface.