The toe pads of treefrogs have inspired a new supersticky yet reusable adhesive. Conventional tape cracks when it is pulled off a surface. The cracks enable removal, but usually also make the tape useless for reuse. The toe pads of treefrogs contain microscopic channels which prevent cracking. The new adhesive does not exactly imitate the natural structures of frog toe pads. Instead, it captures the physics rather than the actual structure of the microchannels. The combined properties of microchannels and a fluid increase surface adhesion of the new elastic material by about 30 times, and since the material itself is elastic it is reusable.
Microfluidic Adhesion Induced by Subsurface Microstructures
Science 12 October 2007: 258-261
Natural adhesives in the feet of different arthropods and vertebrates show strong adhesion as well as excellent reusability. Whereas the hierarchical structures on the surface are known to have a substantial effect on adhesion, the role of subsurface structures such as the network of microchannels has not been studied. Inspired by these bioadhesives, we generated elastomeric layers with embedded air- or oil-filled microchannels. These adhesives showed remarkable enhancement of adhesion (30 times), which results from the crack-arresting properties of the microchannels, together with the surface stresses caused by the capillary force. The importance of the thickness of the adhesive layer, channel diameter, interchannel spacing, and vertical position within the adhesive has been examined for developing an optimal design of this microfluidic adhesive.