Alfred Crosby1
Univ of Massachusetts1
Failure, or fracture, remains one of the most important, yet most challenging, topics in materials science. This challenge is especially true for soft materials, such as hydrogels and biological tissues. Understanding failure in these systems is critical for developing important technologies, from robust prosthetic materials to protective gear for mitigating debilitating injuries. However, the ultra-soft nature of these materials makes quantifying failure processes difficult. Here, we present two recent advances: 1) understanding how cavitation-based deformations lead to either reversible or irreversible damage in hydrogel materials, and 2) new cavitation-based methods for measuring materials properties of buried interfaces between ultra-soft hydrogel materials. For the first topic, we describe the results of a multi-university, multi-disciplinary study that combined the use of precisely-defined polymer networks, molecular dynamic simulations, and classical and new characterization methods to develop and validate of theoretical relationships between molecular network architecture and macroscale cavitation and fracture processes. For the second topic, we are motivated by the critical role that interfacial properties play in determining the failure of biological tissues, as well as ultra-soft materials that are designed to interface with these tissues. We introduce methods that provide straightforward, quantitative measurements of the elasto-adhesion length scale for ultra-soft hydrogel interfaces. These methods provide new means for characterizing interfacial properties within living systems, and they have added benefits of offering pathways for high-throughput characterization of hydrogel adhesion properties, in general. Collectively, the results and discussion presented here are important for enhancing our fundamental understanding of ultra-soft hydrogel materials and the mechanisms that control their failure across a range of size scales.