The innovation engine for new materials

The Role of Friction in Bio-inspired Adhesive Systems

Seminar Group: 


Professor Matt Begley


Mechanical Engineering & Materials Department


Friday, November 8, 2013 - 4:00pm


Life Science Bldg., Room 1001


Prof. Frank Zok

Many plants and animals (notably geckos and mussels) require surprisingly large forces to drive detachment from surfaces, despite being ‘weakly bonded’. This is a consequence of the fact that the force required to disconnect two surfaces is dictated not only by interface bonding, but also the presence of dissipative mechanisms either at the interface or in the bulk of either material. This talk will consider the process of peeling of a thin elastomer film bonded to a glass surface via Van der Waals forces, with two principle goals. The first will be to identify the impact of frictional sliding in the adhered region of the film and its influence on the critical force required to drive peeling. The second will be to make explicit connections between (1) frameworks that utilize the local work of separation (associated with molecular-level bonding) and (2) frameworks that utilize a ‘mixed-mode’ interface toughness in conjunction with an energy release rate based on macroscopic behavior. It will be shown that the strong angular dependence of the force required for peeling is consistent with an ‘adhesion’ model that references only molecular level bonding controlling normal separation. In essence, the model yields a theoretical ‘mixed-mode’ interface toughness that arises from friction in the ‘peeling process zone’. The implications and limitations of the model will be discussed in the context of understanding gecko and mussel adhesion in order to develop novel adhesive systems.