How surface roughness influences the adhesion of soft materials

Research team discovers universal mechanism that leads to adhesion hysteresis in soft materials. Adhesive tape or sticky notes are easy to attach to a surface, but are difficult to remove. This phenomenon, known as adhesion hysteresis, can be fundamentally observed in soft, elastic materials: Adhesive contact is formed more easily than it is broken. Researchers at the University of Freiburg, the University of Pittsburgh and the University of Akron in the US have now discovered that this adhesion hysteresis is caused by the surface roughness of the adherent soft materials. Through a combination of experimental observations and simulations, the team demonstrated that roughness interferes with the separation process, causing the materials to detach in minute, abrupt movements, which release parts of the adhesive bond incrementally. Dr. Antoine Sanner and Lars Pastewka from the Department of Microsystems Engineering and the MatS Cluster of Excellence at the University of Freiburg, Dr. Nityanshu Kumar and Ali Dhinojwala from the University of Akron and Tevis Jacobs from the University of Pittsburgh have published their results in the prestigious journal Science Advances . "Our findings will make it possible to specifically control the adhesion properties of soft materials through surface roughness," says Sanner.