Some Paradoxes in the Description of Mechanical Properties and Fracture Toughness of Hydrogels

ISfIM organized a distinguished lecture on Some Paradoxes in the Description of Mechanical Properties and Fracture Toughness of Hydrogels on 15 February 2023 at School of Mechanical Engineering, Nanyang Technological University, Singapore. The lecture was given by Prof Zishun Liu, Executive Director of International Center for Applied Mechanics, Xi'an Jiaotong University (XJTU), China.

Lecture Abstract:

Hydrogels are widely used in flexible electronics and biomedicine fields because of their excellent large deformation characteristics and very good biocompatibility. Recently, we carried out a series of experiments on polyacrylamide hydrogels with a wide range of water content and reveal that the physical adhesion properties of hydrogels are related to the water content. We find that with a variation of water content, the adhesion energy-water content relationship can be divided into four regions. For double-network (DN) hydrogels, we developed a quantitative framework to decompose the fracture toughness and feature size of the crack-tip field. Through extensive tearing tests, we propose an exponential function to describe the relationship between the apparent fracture energy and free width. The study reveals the physical inconsistencies in some opinions about DN gel fracture and resolves some paradoxes on the toughness of DN gels. Furthermore, through extensive experiments on polyacrylamide gel, we discover scaling-laws that differ significantly in the swollen and dehydrated state in addition to contradicting F-R model. Finally, the recent advances about hydrogel will be discussed in this talk.

Speaker Biography:

Prof Zishun Liu is a Professor of Xi’an Jiaotong University (XJTU) and Executive Director of International Center for Applied Mechanics. He holds the position of director of the Academic Committee of the School of Aerospace Engineering at XJTU. He is also the General Secretary of International Association of Applied Mechanics and the Honorary President of Singapore Association of Computational Mechanics. He is Fellow of International Association of Applied Mechanics, Fellow of International Association of Advanced Materials and SACM fellow. He served on the faculty of XJTU between 1986 and 1994, and as Senior Scientist, Capability Group Manager at Institute of High Performance Computing, Singapore (IHPC), and Associate Professor of NUS at various points from 1999 to 2012. As a visiting scientist, he worked in Max Planck Institute for Metals Research, Stuttgart, Germany and University of Glasgow, UK in 2005 and 2006 respectively. His research interests are in the areas of Mechanics of Soft Materials, Computational Solid Mechanics & Biomechanics, Nanomechanics, Vibro-Acoustic. He has published more than 210 SCI referred research papers and many of his research articles were awarded Most Cited Author Award.

Prof Liu is an active member of various leadership roles in editorial boards and professional communities as follow: Prof Liu is an Editor-In-Chief of Int. Journal of Applied Mechanics and Int. Journal of Computational Materials Science and Engineering, and Editor of Journal of Mechanics of Material and Structures, Associate Editor of Journal of Applied and Computational Mechanics. He also serves on the editorial boards of IJCM, IJSSD, AMS, AMSS etc. Prof Liu has organized, as Chairman, more than 20 International Conferences in the field of computational mechanics & applied mechanics.