On June 30, 2023, Associate Professor Jaehyung Ju (주재형, Zaiheng Zhu) from University of Michigan - Shanghai Jiao Tong University (UM-SJTU) Joint Institute was invited by Professor Jiayao Ma to visit Motion Structures Laboratory of Tianjin University.

Mr. Ju gave an interesting lecture entitled " Magneto-thermomechanically reprogrammable mechanical metamaterials-untethered, reversible, reprogrammable transformations with shape locking". According to the report, future active metamaterials for reconfigurable structural applications require fast, untethered, reversible, and reprogrammable (multimodal) transformability with shape locking. Magnetic control has a superior advantage for fast and remotely controlled deployment; however, a significant drawback is maintaining the magnetic force to hold the transformation, limiting its use in structural applications. The shape-locking property of shape memory polymers (SMPs) can resolve this issue. However, the intrinsic irreversibility of SMPs may limit their reconfigurability as active metamaterials. Moreover, reprogrammable methods have required high power with laser and arc welding, proving to be energy-inefficient control methods. Herein, Mr. Ju’s group aims to construct and demonstrate a magneto-thermomechanical tool that enables a single material system to transform with untethered, reversible, low-powered reprogrammable deformations and shape locking via the application of magneto-thermomechanically triggered prestress on the SMP and structural instability with asymmetric magnetic torque. This work demonstrates the mutual assistance of two physics concepts — magnetic control combined with the thermomechanical behavior of shape memory polymers, without requiring new materials synthesis and high-power energy for reprogramming. This approach can open a new path of active metamaterials, flexible yet stiff soft robots, and multimodal morphing structures, where people can design them in reversible and reprogrammable ways.

Jaehyung Ju is an Associate Professor at the University of Michigan - Shanghai Jiao Tong University (UM-SJTU) Joint Institute at Shanghai Jiao Tong University. He received the 2015 Orr Best Paper Award from the ASME Journal of Engineering Materials and Technology. He was selected for the 2012 Young Engineer of the Year Award from the ASME North Texas Section. His current research interests are in the mechanics and design of mechanical metamaterials with programmable functions. He also explores advanced manufacturing methods, e.g., 3D and 4D Printing technologies, to support fundamental and applied research.