ICTP is pleased to announce that the forthcoming ICTP Colloquium
by Prof. Bo Persson on "The Physics of Contact and Adhesion with
application to biological systems" will take place TODAY
at
17:00 hrs, in the Budinich Lecture Hall, Leonardo
Building, ICTP.
Biosketch: Prof. Bo Persson obtained his PhD in theoretical
physics from Chalmers Technical University 1980. His thesis
advisor was Prof. Stig Lundqvist, one of the founders of condensed
matter at ICTP. He is currently working at the Peter Gruenberg
Institute of the Research Center Juelich, part of Germany’s
Helmholtz Association. Besides several years as a visiting
scientist at IBM research laboratories, in Yorktown Heights and in
Zurich, he spent numerous periods as a visiting scientist in
research laboratories in Israel, Japan, China, Italy, and
elsewhere. After his initial research work in dynamical processes
at surfaces, he turned around 1995 to theoretical tribology
(friction, adhesion, contact mechanics). He has published more
that 400 articles in international journals, and is the author of
"Sliding Friction: Physical Principles and Applications"
(Springer, first edition 1997) and co-author (with Prof. A.
Volokitin) on "Electromagnetic Fluctuations at the Nanoscale:
Theory and Applications" (Springer, 2017), besides the early book
(with E. Tosatti) “Physics of Sliding Friction (Kluwer 1996)
collecting papers of the very first ICTP Research Workshop on the
subject in 1995.
Besides his primary research activity at PGI, Bo Persson is the
founder and CEO of MultiscaleConsulting, a company involved in
consulting (theory and experiment) on topics related to contact
mechanics and friction (see
www.MultiscaleConsulting.com). Most
clients are from the tire industry, two F1-racing teams (rubber
friction and tire dynamics), and medical companies (the contact
between the rubber stopper and the barrel in syringes).
Abstract: One of the
weakest forces in Nature is the van der Waals interaction which
acts between all atoms and solids. Still on a macroscopic level
this force field is very strong: one can theoretically hang an
object with the weight of a car using a solid bar with 1 square
cm cross section attached by the van der Waals interaction to a
flat surface. This is never observed in reality, and in my
presentation, I will explain the origin of this "adhesion
paradox". I will also show how some animals, like the gecko or
tree frog, have "learned" (via natural selection) to make use of
these weak force fields to adhere to rough and contaminated
surfaces, where traditional adhesives would fail. I will
describe the origin of adhesion hysteresis, and present some
experimental results illustrating it. All solid objects have
surface roughness which often is fractal-like, sometimes
extending from the size of the solid object to atomic distances.
I will describe a theory which can be used to study the contact
between two elastic solids with surface roughness and adhesion.
The theory predicts the contact area and the stress probability
distribution, as well as the probability distribution of
interfacial separations, and is the basis for a huge number of
practical applications like rubber friction, adhesion, the heat
and electric contact resistance, leakage of rubber seals,
conveyor belts, tire dynamics etc. It describes how the contact
between two solid objects changes as the interface is studied
with increasing magnification, say from the naked-eye level to
atomic resolution. The theory will be illustrated with
applications to the human skin, to electroadhesion for haptic
touchscreens (involving the finger-glass screen contact), and
adhesive pads for robotics.
Information is available at: http://indico.ictp.it/event/9069/
The Colloquium will be livestreamed at: ictp.it/livestream
Light refreshments will be served after the talk.
You are all very warmly invited to attend.
With best regards,
Office of the Director, ICTP