Active Control of Adhesion Forces Between Wet Surfaces

Capillary and surface effects at the interface between two media enhance adhesion in wet environments. This phenomenon, called wet adhesion, is exploited in nature by some insects and amphibians to stand or walk over wet substrates. Since surface effects are generally voltage-sensitive, as demonstrated, for example, by electrowetting phenomena, one may expect that the strength of wet adhesion could be adjusted by using electric means. Indeed, in this paper, we show that the liquid-mediated adhesion between a flat and a grooved surface, the latter equipped with interdigitated electrodes deposited beneath it, can be reduced by more than 80 %, when a 90 V DC voltage is applied. The described technique points out the possibility of realizing surfaces with tunable adhesive properties, when in contact with wet substrates, which may be useful for several applications, including the development of propulsion systems for autonomous endoscopic robots and the fabrication of microgrippers for the manipulation of small objects.