Seminar | Rong Long: Controlling Fracture, Contact and Adhesion in Soft Materials Through Structural Design

Join Rong Long, professor of mechanical engineering at the University of Colorado Boulder, for a seminar exploring how structural design can be used to control fracture, contact and adhesion in soft materials. Drawing on research in soft elastomers, hydrogels and adhesives, Long will discuss how geometry can be leveraged to direct crack propagation, control interfacial traction and program adhesion, with applications ranging from soft robotics to medical devices.

Abstract

Soft materials such as elastomers, hydrogels, and adhesives underlie technologies ranging from soft robotics to medical devices. Their performance often depends on how they rupture, contact, and adhere to other materials. Because soft materials can undergo large deformation, these processes are strongly influenced by geometry, creating opportunities to control fracture, contact, and adhesion through structural design rather than material chemistry alone. In this talk, I will present studies from my group that explore this concept in three areas. First, I will discuss crack growth in soft elastomers under mixed-mode loading and examine how cracks are deflected by stiff inclusions. Second, I will examine the contact mechanics between micropillar arrays and soft hydrogel substrates, motivated by balloon catheters that must anchor to soft, slippery tissues. Using three-dimensional imaging, we showed that the shear traction generated by micropillars is governed by local lateral contact between the pillars and the deformed substrate. Third, I will discuss adhesive tapes with patterned cuts that result in direction-dependent peel force, as well as the emergence of interfacial cavitation during the peeling of soft viscoelastic adhesives. Together, these studies demonstrate how structural design can be used to direct crack propagation, control interfacial traction, and program adhesion in soft materials. 

Bio

Rong Long is currently an Associate Professor and Lyall Faculty Fellow in the Department of Mechanical Engineering at University of Colorado (CU) Boulder.   Prior to joining CU in 2014, he was an Assistant Professor at University of Alberta in 2013-2014, a Research Associate at University of Colorado in 2012, and a Postdoctoral Associate at Cornell University in 2011.  He received his Ph.D. degree in Theoretical and Applied Mechanics from Cornell University in 2011 and his B.S. degree in the same field from University of Science and Technology of China in 2006.  He received a few awards including the Young Adhesion Scientist Award (2014), the 3M non-Tenured Faculty Award (2017), the National Science Foundation CAREER Award (2018) and the Provost’s Faculty Achievement Award (2020).  His research interests include continuum mechanics of soft materials, fracture mechanics, contact mechanics, adhesion and biomechanics.