Heinrich Jaeger, William J. Friedman and Alicia Townsend Professor of Physics, University of Chicago.
Dr. Jaeger opened his presentation by remarking that granular materials exhibit far-from-equilibrium behavior. This behavior can be adaptive, and can yield a smart aggregate response from “dumb” ingredients. His work at the University of Chicago deals with granular1 materials that can be used to form adaptive matter. These include pouring granular materials into a form, designing high strength, low-density structures, and making granular matter jam and unjam based on externally applied stress. This latter project was part of the completed JamBots program at DARPA. Research on granular matter can be traced back many years, but only recently has granular matter become of interest as an adaptive material.
Dr. Jaeger discussed both mesoscopic and macroscopic granular matter and then went on to discuss jamming. He mentioned that jamming is the emergent, cooperative process of a collection of objects getting stuck and becoming rigid. Jamming underlies some of the major scientific challenges in far-from-equilibrium physics, including understanding the glass transition. He noted that some researchers are working on optimizing the packing density of particles. Dr. Jaeger described how there has been rapid recent progress in simulating large collections of non-spherical particles, which has happened due to better computing hardware and algorithms.
Dr. Jaeger described soft robotics where jamming is the enabling technology. He showed different robots that can adapt to the surface of their structures, and also other structures that can adapt themselves to different surfaces (such as gripping a glass of water). An example is a robotic arm that can throw a dart onto a dartboard. These are passive, underactuated type universal grippers, being researched here in the United States.
In summary, Dr. Jaeger stated that granular materials are pervasive across all industries and technology with multitudes of applications. Granular matter is an amorphous collection of many (hard) particles, with interactions dominated by interfaces, and can be viewed as prototypical of far from-equilibrium behavior. Jamming is an important mechanism to produce reversible transformation between soft/rigid states in granular systems. He concluded by noting that with the proper design, granular materials can be adaptable, robust, and possibly “self-healing.”
Q – What is around the corner? A – Jaeger responded with three topics: exploit particle shape, make ingredients “smart,” and adaptive granular matter by design.
Q – Can you create materials that operate in a certain frequency range, and respond to sound waves? A – Yes, he said, research is being conducted to create materials that respond to certain frequency ranges. Sound waves are not yet being thoroughly researched (explorations are just preliminary).
Daniel Inman, Department Chair, Aerospace Engineering and Clarence “Kelly” Johnson Professor, University of Michigan.
Dr. Inman presented to the workshop via video conferencing. He opened his presentation by outlining the areas that he would discuss. They included Morphing Aircraft, Solar Powered Aircraft, Structural Monitoring, Energy Harvesting, Origami Structures and Multifunctional Hybrids. Dr.
1Dr. Jaeger described granular matter as an amorphous collection of many (hard) particles in which emergent behavior arises from interaction at interfaces, and the internal particle properties are less important.