Dynamics of High-Speed Adhesive Detachment

The science of adhesion is often focused on how things stick, but many open questions also remain about the physics of how sticky stuff unsticks. We use optical microscopy and high-speed imaging to measure the surface profiles of soft, sticky, solid silicone gels as they undergo rapid, high-strain deformation from the final moments of adhesion through detachment and subsequent relaxation. We observe that the soft adhesive substrates always detach from a single point on an adhered, rigid sphere, independent of the sphere size and the initial contact area. After detachment, the height of the relaxing surface decays as a power law in time and the surface profile is self-similar, both suggestive of a detachment singularity that is distinctly different from liquid break-off. We further explore the competition between surface and bulk effects by varying the material properties of the adhesive substrates, as well as the size and surface energy of the spheres.