MechE Colloquium: Mechanics of wrinkled structures


Event details

Date 08.03.2022
Hour 12:0013:00
Speaker Prof. Andrej Košmrlj, Mechanical and Aerospace Engineering, Princeton University
Location Online
Category Conferences - Seminars
Face masks are recommended for in-person attendance in MED 0 1418.

Wrinkling instability of compressed stiff thin films bound to soft substrates has been studied for many years and the formation and evolution of wrinkles is well understood. Similar wrinkling instabilities also play important role in biology during the development of organs, such as brains and guts, and during the formation of bacterial biofilms grown on soft substrates. In recent years, the wrinkling instability has been exploited to create structures with tunable drag, wetting, adhesion, and to create a template for wire formation. While these studies successfully demonstrated the proofs of concepts, quantitative understanding is still lacking, because very little is known about how wrinkled surfaces deform in response to interactions with the environment. To address this issue, we investigated the linear response of wrinkled structures to external forces. By mapping the problem to the Landau theory of phase transitions, we demonstrated that the linear response to external forces diverges near the onset of wrinkling instability with the usual mean-field exponent found in critical phenomena. Interactions with the environment also dictate the morphology of wrinkled patterns in growing biological systems. I will discuss the formation of wrinkling patterns in bacterial biofilms grown on agar substrates, which usually have radial stripe patterns near the outer edge and zigzag herringbone-like patterns in the core. The observed wrinkling patterns result from uneven stress distribution in the biofilm as a consequence of the depletion of slowly diffusing nutrients underneath the biofilm, which are required for bacterial growth.

Bio: Andrej Košmrlj is an assistant professor of Mechanical and Aerospace Engineering at Princeton University. Andrej Košmrlj received his Ph.D. in Physics from the Massachusetts Institute of Technology in 2011, and his postdoctoral training at Harvard University. He joined Princeton University in 2015, where his group is doing theoretical and computational research on complex systems ranging from materials science to the physics of living systems. For his research achievements, Andrej Košmrlj has received the NSF Career Award and the Alfred Rheinstein Faculty Award. For his teaching efforts, Andrej Košmrlj has received the Excellence in Teaching Award from the School of Engineering and Applied Science.

Practical information

  • General public
  • Free



MechE Colloquium: Mechanics of wrinkled structures