"Adhesion, Friction & Lubrication of Surfaces & Liquid Films and their Relation to Diverse Phenomena Such as how Geckos Climb on Walls and Ceilings, Surface Damage, and Sensing" by Professor Jacob Isrealachvili, Chemical Engineering, University of California Santa Barbara, United States
Many diverse and seemingly unrelated phenomena at the macroscopic level, in both physical and biological systems, have a common origin at the microscopic and nanoscopic (atomic / molecular) levels. This talk will review the fundamental aspects of adhesion, stiction, friction (of dry and liquid lubricated surfaces), and give examples of everyday processes where adhesion and friction forces act simultaneously, such as the way geckos and small robots climb on walls and ceilings. It is also becoming increasingly apparent that friction forces and frictional motions are rarely constant or ‘steady’, but proceed in intermittent jumps, commonly referred to as ‘stick-slip’ sliding, which can be regular (periodic) or irregular (random or chaotic), and can occur at the nano, micro, and macro-scales (including seismic dimensions). These different types of ‘intermittent’ motions are central to earthquakes and to many biological motions and sensory perceptions, including how blood cells move along capillary walls during immune recognition processes, food-texture (mouth feel), and other types of tactile perceptions. Stiction and stick-slip sliding is also a main cause of damage to surfaces and biological tissues. I will also describe recent and ongoing experiments, mainly using the Surface Forces Apparatus (SFA), for measuring these forces.