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Séminaire de Al Crosby

Polymer-Nanoparticle Mesostructures and the Puncture of Soft Gels

Alfred J. Crosby Polymer Science & Engineering Department University of Massachusetts Amherst

We will discuss two current projects in our group. The first project focuses on addressing a critical challenge in the ability to transform advanced materials components synthesized at the nanoscale into robust macroscale structures. In nature, this challenge is addressed through the assembly of nanoscale building blocks, e.g. proteins, into mesocale structures, e.g. fibrils, helices, and sheets, which subsequently assemble into structures with enhanced properties and functions. Taking inspiration from these ubiquitous principles that promote scalability in nature, we are developing processes to assemble synthetically tailored nanoscale building blocks into robust mesoscale structures, including fibrils, helices, and sheets. These transformation processes take advantage of the balance between surface energy and elasticity, leading to a robust, geometric approach for secondary and tertiary structure formation. We have initiated a thorough study of the mechanics of these structures, which offer promise in applications ranging from flexible electronics to advanced coatings.
The second project focuses on understanding the deformation mechanisms associated with puncturing a soft material, such as a gel or biological tissue. Puncture is a ubiquitous process associated with a large variety of applications, especially in clinical medicine ; however, fundamental knowledge on the mechanics of puncture is limited. We have initiated a broad study into the mechanics of puncture in synthetic gels and have discovered several interesting and potentially impactful relationships. Interestingly, we observe that the nominal stresses prior to puncture can exceed several 100 times the Young’s modulus for soft gels. We analyze this behavior, as well as related results, in terms of stress and energy limited regimes for crack nucleation. Overall, these stories will provide insight into how we think as a group and learn from nature, without losing focus on the importance of fundamental materials principles and engineering design.


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