Mechanical Engineering Graduate Seminar Series: Professor Ruobing Bai, Northeastern University, "Multifunctional polymer mechanics towards intelligent and sustainable mechanical systems"

Abstract: Multifunctional polymers have emerged as a transformative class of materials, enabling new advancements across robotics, manufacturing, sustainability, energy storage, and human-machine interfaces. These materials, ranging from stiff molecular crystals, semicrystalline polymers, to highly stretchable elastomeric networks, respond dynamically to stimuli such as chemistry, heat, and light. Therefore, rational designs of their composition, microstructure, geometry, and architecture would enable a new paradigm of physical intelligence, integrating actuation, sensing, and analysis directly into the material without a need for centralized computing or complex controls. This concept of “The Material Is the Machine” significantly expands the design space for machine intelligence beyond the classical von Neumann architecture. This talk presents our latest research on multifunctional polymer systems, focusing on the fundamental mechanics coupled with other physical and chemical processes. We start by investigating the thermo- and photo-responsive phase transformation in liquid crystal polymer systems, as well as their potential for actuation and shape morphing through theory, simulation, and experiment. These studies reveal the fundamental photo-thermo-mechanical coupling across length scales and its impact on macroscopic behaviors of the material. Furthermore, we study the role of thermo-responsive phase separation in enabling highly switchable adhesion between bonding and debonding in soft sticky adhesives. By incorporating rationally designed external controls and surface architectures, these adhesives pave the way for new approaches to sustainable manufacturing and device recycling. This talk is hoped to advance the fundamental mechanics of emerging multifunctional polymers, bring together diverse research communities, and expand the potential large-scale applications that address emerging engineering challenges.

Bio: Ruobing Bai is an assistant professor in the Department of Mechanical and Industrial Engineering at Northeastern University. He completed his bachelor, PhD, and postdoc training at Peking University, Harvard University, and California Institute of Technology, respectively, all in solid mechanics. He is the recipient of the Chun-Tsung Scholar (Peking University), the ASME (American Society of Mechanical Engineers) Haythornthwaite Research Initiation Award, the EML (Extreme Mechanics Letters) Young Investigator Award, and the ACS (American Chemical Society) Petroleum Research Fund Doctoral New Investigator grant. He is currently a member of the Extreme Mechanics Letters (EML) Early Career Advisory Board and the secretary of the ASME “Mechanics of Soft Materials” technical committee. His research combines theory and experiment in solid mechanics, materials science, and other multiphysical processes in areas including but not limited to multifunctional materials, fracture, adhesion, strengthening and toughening, sustainable materials, soft robotics, human-machine interfaces, and energy storage systems.