Surfaces and materials which are able to reversibly switch their hydrophobicity/hydrophilicity in response to external stimuli such as changes in pH, have a wide variety of potential applications.

Researchers lead by Spiros Anastasiadis, Univeristy of Crete, Greece, have grafted a pH-responsive material, PDPAEMA, on to a substrate, which could be used in microelectromechanical systems (MEMS) and lab-on-a-chip devices. The material can be switched between being highly water repellant to superhydrophobic but does so with the opposite character to previously developed materials. At high pH the new material is superhydrophobic.

This property will allow microfluidics devices that exploit the behavior to be used with cells, proteins and nucleic acids, which undergo unwanted interactions at high pH with hydrophilic materials.

• From superhydrophobicity and water repellency to superhydrophilicity: smart polymer-functionalized surfaces
  E. Stratakis, A. Mateescu, M. Barberoglou, M. Vamvakaki, C. Fotakis, S. H. Anastasiadis,
  Chem. Commun. 2010, 46, 4136.
  DOI: 10.1039/c003294h