AdhesiPS

Simultaneous control of adhesion strength and detachment dynamics of soft adhesive materials is a key improvement lever for industrial applications especially during assembly and converting processes. AdhesiPS is a fundamental research program that investigates how substrates patterned with micro-structured 3D topography and chemically-induced adhesive heterogeneities can be used to control the bonding and debonding process of a soft adhesive over a very wide range of strain-rates. AdhesiPS plans to use micro-structured interfaces with different geometrical patterns to control the adhesion of viscoelastic polymer adhesives, in addition to chemical control of the adhesive formula or substrate. Thanks to modifications of the pattern geometry and physical properties (stiffness, interfacial energy) of the substrate, the AdhesiPS project will find strategies to tune the adhesion of soft adhesive for extreme conditions, from much lower to much higher values than the one on a smooth surface. This possibility is strongly encouraged by the fact that such a tuning has already been demonstrated for patterned rubber-like elastomers and that similar mechanisms are responsible for adhesion energy in soft adhesives and in patterned elastomers, in particular the hysteretic loss of elastic energy stored and eventually dissipated during the debonding process. Interestingly, in the case of a soft adhesives on a patterned substrate, elastic loss may come both from the substrate and from the fibrillation mechanism in the adhesive. Micro-structures that are able to reduce the contact area between the adhesive and the substrate, and increase the slip at the interface, would also be very good candidates for creating very low adhesion substrates, in a similar way that some micro-structured interfaces have superhydrophobic properties. Furthermore, both the substrate and adhesive contribution to the adhesion energy are strain-rate dependent. Adjusting the different strain-rate dependence of the substrate contribution to adhesion compared to the one of the adhesive could also provide a path towards varying in a controlled manner the level of adhesion as a function of the strain-rate. For instance, it may become possible to find conditions under which the contribution of the substrate to the adhesion, increasing with strain-rate, could compensate the decrease of the adhesion energy of the soft adhesive observed at high strain-rate on a smooth substrate, which would be useful for avoiding peeling stick-slip instabilities. More generally, industrial processes that require a different level of adhesion on two opposite sides of a polymer film, or that need a different level of adhesion during assembly and during final usage could take advantage of a pattern-dependent and strain-rate dependent tuning of adhesion.