Thermal/plasma-driven reversible wettability switching of a bare gold film on a poly(dimethylsiloxane) surface by electroless plating.

We report an approach for fabricating a tunable wettability surface by electroless gold plating on poly(dimethylsiloxane) (PDMS). A two-layer structured gold film with a tight layer and a loose layer can be obtained on the surface of a PDMS chip when the PDMS chip is immersed in a gold plating solution at 30 degrees C for 4 h. Its wettability can be rapidly switched between superhydrophilicity and superhydrophobicity by plasma and heat treatments without any self-assembled monolayer, and the superhydrophobicity can be even changed from the gecko-foot-hair-like character to the lotus-leaf-like character. Benefiting from the various wettabilities of the prepared gold/PDMS composites, protein patterning is successfully achieved on a patterned superhydrophobic/superhydrophilic gold/PDMS composite; a superhydrophobic needle for transferring supersmall water droplets (1 microL) to a superhydrophobic surface is successfully fabricated.