Woodruff School of Mechanical Engineering
Faculty Candidate Seminar
Bionics in tribology: frictional dress of elastomeric surfaces
Dr. Michael Varenberg
Technion - Israel Institute of Technology
Monday, April 14, 2014 at 11:00:00 AM
MRDC Building, Room 4211
Dr. Itzhak Green
To secure their locomotion on a variety of natural substrates, terrestrial animals have evolved attachment systems based on smooth and hairy pads. Smooth pads are always wet and usually possess surface texture of different shapes, of which the most striking is the hexagonal one found in bush crickets, mushroom-tongued salamanders and tree frogs. Hairy pads may be either wet or dry and, in most cases, bear spatula-shaped tips appeared independently in insects, arachnids and reptiles. Inspired by the questions of what mechanisms are hidden behind the spectacular tribological performance of biological attachment systems and whether they can be used in technical applications, we mimic both hexagonally-textured and spatula-bearing surfaces using elastomeric materials. Tested for adhesion and friction with simultaneous visualization of the contact zone evolutions, biomimetic surfaces demonstrate a range of properties related to arresting and facilitation of relative motion. In hexagonally-patterned surfaces, these are elimination of stick-slip instabilities, suppressing of hydroplaning and ability to tune friction from 50% to nearly 100% of that measured on a smooth reference. In spatula-inspired surface microstructures, we observe a friction coefficient of as high as 10 when that measured on a smooth reference is about 1.3, which have already drawn the interest of the semiconductor industry looking for clean, cheap and safe mechanisms of silicon wafer gripping.
Michael Varenberg received his PhD degree in 2004 from Technion – Israel Institute of Technology. After spending 3 years as a Guest Scientist at the Max Planck Institute for Metals Research in Germany, in 2007 he joined the Department of Mechanical Engineering at Technion as an Assistant Professor in Tribology. His research interests are in friction and wear of engineering surfaces, micro/nano tribology, bionic tribology, tribological instrumentation and contact mechanics.