A superhydrophobic to superhydrophilic in situ wettability switch of microstructured polypyrrole surfaces

We present an electrochemical layered system that allows for the fast, in situ wettability switch of microstructured PPy upon the application of an electric stimulus. We have eliminated the need for PPy to be immersed in an electrolyte to switch between wetting states, laying the groundwork for PPy to be used as a viable material in many applications, including microfluidics or smart textiles. The PPy surface was switched from the superhydrophobic state (contact angle=159) to the superhydrophilic state (contact angle=0) in 3 s. A wettability gradient was also created on a PPy surface using the layered system, causing a 3 µL droplet to travel approximately 2 mm in 0.8 s.