MECH6090 PG Seminar
Frictional motion plays a central role in diverse systems and phenomena that span vast ranges of scales, from the nanometer contacts inherent in micro- and nanomachines and biological molecular motors to the geophysical scales characteristic for earthquakes. Despite the practical and fundamental importance of friction and the growing efforts in the field, many key aspects of dynamics of friction are still not well understood. One of the main difficulties in understanding and predicting frictional response is the complexity of highly non-equilibrium processes going on in any tribological contact which include detachment and re-attachment of multiple microscopic contacts (bonds) between the surfaces in relative motion while still in contact.
In this lecture I will discuss microscopic models, which establish relationships between the interfacial dynamics and frictional phenomena. In particular, I will show that experimentally observed velocity and temperature dependencies of nanoscale friction can be rationalized by explicitly considering the influence of temperature on the formation and rupturing of microscopic contacts. Understanding microscopic mechanisms of frictional phenomena allowed us to suggest new ways to switch and control surface interactions, reversibly and non-invasively, at the molecular level, and thereby tune friction. I will focus on three approaches to control frictional forces: (i) using incommensurate "superlubric" contacts, (ii) via application of electric field and (iii) via externally imposed vibrations of small amplitude and energy. The ability to control and manipulate friction during sliding is extremely important for a large variety of applications in automotive and electronics industries, and even in medicine.
Professor Michael Urbakh is an expert in theoretical condensed matter and chemical physics and and their applications to electrochemistry, nanoscience, and biophysics. Through the years his particular areas of research were nanotribology, single molecule force studies, atomic scale engines, equilibrium and kinetic properties of metal/electrolyte liquid/liquid interfaces, electrowetting, optofluidics and, electrotunable optical devices.
Michael Urbakh started his career at the Frumkin Institute of Electrochemistry (Acad.Sci.), Moscow and in 1990 he moved to the School of Chemistry, Tel Aviv University, where he is now a professor of Chemistry, Chairman of the School of Chemistry and a Head of the Ratner Institute of Single Molecule Chemistry.
Awards and Honors:
2013: XIN Fellow, Tel Aviv –Tsinghua (Beijing) Universities
2012: The Josef Kryss Chair in Chemistry at Surfaces and Interfaces
2010: Alexander Kuznetzov Prize for Theoretical Electrochemistry by the International Society of Electrochemistry
He has published over 240 original and 20 review and monographic articles in leading journals and filed several patents. He was entitled to organize and direct many international conferences including number of symposia at MRS meeting in Boston, meetings at the International Centre for Theoretical Physics, Trieste, CECAM meetings in Lion, Lausanne and Tel Aviv, Faraday Discussions in Cambridge, and meetings of Israel Electrochemical society.
To distinguish just a few directions for his research: Michael Urbakh is considered as a world-renowned leader in in the theory of friction at the nanoscale and theoretical studies of electrical and optical properties of electrochemical interfaces.