MechE Colloquium: Autonomously Moving and Assembling Soft Matter Systems

Abstract: Soft materials, such as polymer gels, have long been realized as a potential platform foractuation; however, several challenges have limited their integration into translatable technologies. In particular, soft matter actuators are slow, unable to generate significant power, and typically require external intervention to initiate multiple, sequential actuation events. Here, we describe our efforts to meet these challenges. We first introducematerials science principles and lessons that we have learned as part of a multi-university team, which takes inspiration from examples in nature including mantis
shrimp and trap-jaw ants. These organisms use Latch-Mediated Spring Actuation (LaMSA) to achieve high power, impulsive movements by integrating actuators, elastic elements, and stability-mediating latches. We demonstrate how transient metastable deformations associated with swelling and deswelling of a polymer gel can be exploited to generate mechanical bi-stability, giving rise to multiple, self-repeating, snap-through
movements. Second, we describe the use of structural asymmetry to mediate swelling/deswelling processes in order to control the kinematics of mesoscale polymer ribbons. We use this control to form bundled structures that resemble powerful biological actuators, e.g. muscles, and their formation processes open pathways for creating a future generation of materials that have textile-like properties without requiring energy
intensive spinning and weaving processes. Collectively, the strategies and results discussed here provide new insight into how polymer properties can combine with purposeful structural design to achieve complex tasks, which can be used in the development of microscale robots and new adaptable composite materials.


Biography: Alfred J. Crosby is Professor and Head of the Polymer Science & Engineering Department at the
University of Massachusetts Amherst and Co-Director of the Center for Evolutionary Materials. Al received his B.S. in Civil Engineering and Applied Mechanics from the University of Virginia and his Ph.D. in Materials Science & Engineering from Northwestern University. He was an
NRC Postdoctoral Fellow at NIST from 2000-2002 before joining UMass Amherst in 2002. He has received numerous awards, including being a Fellow of the American Physical Society and the National Academy of Inventors, and his research has been covered extensively in the popular
media. He serves on several advisory boards and is the Editor-in-Chief for the Royal Society of Chemistry journal Soft Matter.