Tape Loop Adhesion

A common method of adhering two parallel surfaces to each other is to place a tape loop between them. Despite the tape loop’s prevalence there has, to our knowledge, been no full description of the mechanics of this system to date. We attack the problem experimentally using a reduced half-loop geometry, which is moved through a compression-retraction (sticking then peeling) cycle from which force-displacement curves are measured. We also imaged the shape of the loop during the experiment with photography and laser scanning confocal microscopy. By using both polydimethylsiloxane (PDMS) and polycarbonate (PC) as ‘tape’ materials, we explored the mechanics of both ‘tacky’ and dry adhesive systems. Notably, we find that the compression curve is completely insensitive to surface interactions. Adapting the ‘sticky-elastica’ model of Majidi and Vella, we show how the entire cycle can be described using only an elastic modulus and critical energy release rate as inputs. Remarkably, a complete model of the cycle allows us to create an incredibly simple measurement of adhesion, involving only a ruler.