Surfaces -defined as the interfaces between solids and liquids- have attracted much attention in optics and biology, such as total internal reflection imaging (TIRF) and DNA microarrays. Within the context of optofluidics however, surfaces have received little attention. In this paper, we describe how surfaces can define or enhance optofluidic function. More specifically we discuss chemical interfaces that control the orientation of liquid crystals and the stretching of individual nucleic acids, diffractive and plasmonic nanostructures for lasing and opto-thermal control, as well as microstructures that read pressure and form chemical patterns. © 2010 SPIE.