Mechanics of Interfaces with Switchable Adhesion

Distinguished Speaker

Kevin T. Turner

Professor & Chair

Mechanical Engineering and Applied Mechanics

University of Pennsylvania, Philadelphia

Abstract: Adhesive interfaces are typically engineered to provide strong and permanent bonding, however applications in robotics and manufacturing have motivated the development of interfaces with switchable adhesion. The effective adhesion strength of an interface can be modulated through control of the surface interactions as well as the local stress-state at the interface. In all cases, the mechanics of the interface must be engineered to realize high adhesion strength in one state and low adhesion in the other state. Here, a general mechanics-based framework for designing interfaces with switchable adhesion is presented and multiple systems are demonstrated. In one class of systems, structured elastic heterogeneity is used to tailor the stress distribution at the interface and hence the effective adhesion strength. Fracture-mechanics based models, analytical and computational, are used to design systems that can be tuned passively via loading direction or actively via stiffness modulation of one component. The performance of these systems is experimentally validated and applied in pick-and-place and microtransfer printing processes. In a second class of systems, electrostatic adhesion is used modulate interface behavior. Modeling and experiments show that realizing adhesion capacity and the switching ratio require careful control of both the overall contact geometry as well as the fine scale roughness of the surfaces for electroadhesion to be exploited effectively.

Bio: Kevin T. Turner is a Professor and the Department Chair of Mechanical Engineering and Applied Mechanics at the University of Pennsylvania. He holds a secondary appointment in Materials Science and Engineering and is the Penn site director of the NSF-funded Engineering Research Center for Internet of Things for Precision Agriculture (IoT4Ag). He received his BS from the Johns Hopkins University and SM and PhD from the Massachusetts Institute of Technology. He has received numerous awards, including the Lindback Award for Distinguished Teaching, ASME Sia Nemat-Nasser Early Career Award, Adhesion Society - Young Adhesion Scientist Award, and NSF Career Award. Turner's research is at the nexus of mechanics, manufacturing, and materials. Ongoing research efforts in Turner's group include materials with tunable adhesion, friction, and stiffness for applications in robotics, design of heterogeneous and additively manufactured materials, and printed and biodegradable sensors for IoT applications.