Hydrogels—soft materials made of mostly water—have many current applications such as contact lenses and as scaffolding materials for tissue engineering. They have potential future applications that could include artificial cartilage and muscles for soft robots. A shortcoming of simple hydrogels is that they easily fail. This severely limits their practical use in load bearing components.
In recent years, however, chemists have invented hydrogels that are highly resistant to fracture. The network of this new class of hydrogels consists of molecular chains linked to each other by different types of connectors (bonds). Engineers do not currently have the predictive tools to determine how components made of hydrogels change shape under load and when they break.
Chung-Yuen Hui and Alan T. Zehnder, Mechanical and Aerospace Engineering, are developing such predictive tools. Hui and Zehnder are addressing current issues that affect the time-dependent mechanics and deformation of hydrogels: performing experiments on a tough polyampholyte hydrogel; developing quantitative models relating nonlinear viscoelastic behavior to bond breaking and reformation kinetics; developing experimental methods to discover and to quantify crack shielding; and developing efficient time integration schemes to solve the nonlinear viscoelastic equations.
The project will advance the field of mechanics by building a framework for development of time-dependent constitutive and fracture models that are linked directly to the microstructure. The end product will be a quantitative method and a computer code which allow engineers to design and analyze components made of hydrogels.