A wettability switchable surface by microscale surface morphology change

A novel wettability switchable surface which shields out any interference from driving energy is demonstrated. In this mechanism, a free-standing metal/polymer membrane with hydrophobic microposts is sustained by spacers, and electrostatic force is used to carry out the deflection of the metal/polymer membrane, hence changing the surface morphology as well as the fraction of a liquid/solid interface. Water contact angles under this mechanism can be manipulated from 131° to 152°, depending on the fraction of a liquid/solid interface. Since the driving energy of electrostatic action is shielded out by the ground electrode, the ingredients carried in the droplet can be thoroughly free from the interference and maintain functionality. Therefore, this mechanism has great potential to manipulate microdroplets for digital fluidic systems in bio-applications. Corrections were made to this article on 8 February 2007. The corrections were made to the authors' affiliation details and on page 491 below equations (2) and (3). The corrected electronic version is identical to the print version. © 2007 IOP Publishing Ltd.