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Zheng Jia (Zhejiang University)
Multiscale Toughening Mechanisms of Soft Materials
Abstract :
Hydrogels and elastomers with high toughness play critical roles in nature and in various engineering applications. Although various mechanisms for toughening soft materials have been reported over the past decades, this classic area – i.e., developing tough soft materials – is still evolving rapidly. In this talk, we will report on several recent efforts to toughen soft materials via mechanisms at various length scales. First, we will present the design of liquid-free ionic conductive elastomers (ICE) toughened by lithium bonds. The liquid-free ICE can defeat the conflict between strength and toughness by utilizing the massive lithium bonds formed between dissolved lithium salts and polymer chains. The ICE is toughened at the bond scale. Next, we will report a highly flaw-insensitive PAAm hydrogel with a fractocohesive length on the scale of centimeters. The highly flaw-insensitive behavior is attributed to the plastic crack blunting that results from the damage of highly inhomogeneous network of very loosely crosslinked PAAm network. The highly inhomogeneous PAAm hydrogel is toughened at the chain scale. Third, we will report a heterogeneous polymer network (HPN) that exhibits multiscale material heterogeneity (patterns at the macroscale and phase separation at the microscale). The HPN is formed by selective polymerization of polymerizable ionic liquids contained in a thermoplastic polyurethane network using digital light processing. The HPNs demonstrate high fracture/fatigue resistance and is toughened at both the macroscale and the phase scale.
Brief Bio :
Dr. Zheng Jia is a tenured associated professor in the Department of Engineering Mechanics at Zhejiang University. He obtained his Ph.D. from the University of Maryland - College Park under the supervision of Prof. Teng Li in December 2014. He was a visiting Ph.D. student in Prof. Zhigang Suo’s group at Harvard University between February 2024 and July 2024. He is serving as the associate director of the institute of applied mechanics of Zhejiang University and the special EML editor of Extreme Mechanics Letters. His research interests include mechanics modeling of soft materials, the design and synthesis of functional hydrogels and elastomers, and the manufacturing of ionotronic devices and flexible structures. Dr. Zheng Jia has published 60+ peer-reviewed journal articles in journals including Nature Communications, Advanced Materials, PNAS, Nano Letters, ACS Nano, and the Journal of Mechanics and Physics of Solids. He has been honored with the Extreme Mechanics Letters Young Investigator Awards in 2019.