CHEG Fall Seminar Series: Chemomechanics of Soft Hydrated Materials

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Abstract

Soft, hydrated materials made up of a polymer network and a solvent are ubiquitous in nature, from cells, tissues to organs. They are also important engineering materials. For example, various hydrogels have been widely used as a cell culture scaffold, drug carrier, dressing, microfluidic device, sensors, actuators, flexible robots, fuel cell membrane, and many others. Defying classical definitions of solid and fluid, these materials are both solid and fluid. The liquid component also provides an ideal medium to host chemical reactions. The coupled liquid flow, chemical reaction, and lattice deformation make the response of materials complex enough that there is enough room for new understandings linking mechanics, chemistry, and materials. In this work, we present a rigorous non-equilibrium thermodynamic framework that couples large deformation, reaction and diffusion to study the fully coupled chemomechanical behaviors of these soft hydrated materials. With a particular system, light-sensitive gels, we demonstrate how the model can be used to design better materials with unique opto-electro-chemo-mechanical properties. To calibrate the model, we need a robust method of material characterization. Despite their importance, experiments that promote these fundamental studies of the multi-physical behaviors of hydrated soft materials are still scarce due to many practical challenges in material characterization. Our work explores this important area by developing a indentation method which can be easily performed using atomic force microscope (AFM). Within the framework of the theory of poroelasticity for the coupled diffusion and strain, we have shown that a unified solution can be obtained for the cylindrical punch, the spherical indenter and the conical indenter. The solutions are summarized in remarkably simple forms allowing easy extraction of material parameters, including mechanical and transport properties. The method is demonstrated on various gels using AFM.

About the speaker

Dr Yuhang Hu is currently Associate Professor at the George W. Woodruff School of Mechanical Engineering and the School of Chemical and Biomolecular Engineering at the Georgia Institute of Technology. Dr. Hu obtained his BSc in Mechanical Engineering from Jiao Tong University in Shanghai, People’s Republic of China in 2005, MSc in Civil and Environmental Engineering from Nanyang Technological University in Singapore in 2007, MSc in Physics from Harvard in 2009 and a PhD in Engineering from Harvard in 2011. She was a postdoctoral fellow at Harvard’s Wyss Institute from 2011 to 2014 to study bio-inspired materials. In 2015, she joined the Faculty of Mechanical and Engineering Sciences at the University of Illinois at Urbana Champaign as an Assistant Professor and moved to Georgia Tech in 2018. Her research focuses on the chemomechanics of soft active materials. , an interdisciplinary field between the mechanics and chemistry of polymers. His work involves both theory and experimentation. She is the recipient of the NSF CARRER Award, the AFOSR YIP Award, the Extreme Mechanics Letters Young Investigator Award, the Journal of Applied Mechanics Award, the ASME Sia Nemat-Nassar Early Career Award and the SEM James W. Dally Young Investigator Award.


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