Using microfluidics to control soft adhesion

Abstract

We demonstrate that the inclusion of subsurface microfluidic features in a soft polymer surface, whose internal pressure can be varied, may be used to modify the effective radius of curvature of the contact and thus switch the magnitude of the adhesion of the surface to a harder counterface from one state to another – in other words to control the ‘stickiness’ of the surface. In these circumstances, adhesion depends on van der Waal forces and can be described by the classic treatment of Johnson, Kendall and Roberts. The pressurization of the subsurface chambers results in the rapid emergence of surface features with reduced radii of curvature which drastically decreases the area available for contact so providing a reduction of up to 90% in the adhesion force of a surface from its original ‘sticky’ state. It is demonstrated that this mechanism can provide a quick, reversible and clean detachment.