Date: Friday, Oct 29th
Presenter: Michael Thouless, Mechanical Engineering and Materials Science and Engineering, University of Michigan
A series of parallel cracks can propagate across a stiff film supported on a compliant substrate when it is subjected to a tensile strain. When films are formed by oxygen plasma or by deposition of metals on an elastomeric substrate such as PDMS, the crack patterns can form the basis of devices such as adjustable channels that can be used for biological or nano-technological applications. In addition, the fracture patterns exhibit some features that have not been previously addressed in analyses of thin-film cracking. In particular, the cracks channel through both the film and the substrate, with the depth of the cracks being up to two orders of magnitude larger than the thickness of the film. A general mechanics analysis for this problem examines how the properties of the film and compliant substrate control these crack patterns.
Michael Thouless is a Professor of Mechanical Engineering and a Professor of Materials Science and Engineering at the University of Michigan in Ann Arbor. He read engineering as an undergraduate at Churchill College from 1978-1981. He got an MS (1982) and a PhD (1984) in Materials Science from the University of California at Berkeley, doing research on the high-temperature failure of ceramics. He then did a post-doc at UC Berkeley and UC Santa Barbara working on ceramic composites and on the mechanics of thin films. From 1987-1994, he was a Research Staff Member at the IBM Research Division in Yorktown Heights, continuing to work on the mechanics of interfaces and thin films, He moved to the University of Michigan in 1995. At Michigan, he has continued to work on the mechanical properties of materials and on the mechanics of adhesion and fracture. He is a fellow of the ASME, and received his Sc.D. from Cambridge University in 2009.