Mechanics of Deformation of Flexible Fibrous Networks

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Many useful materials are made up of interconnected networks of fibers. This is observed both in biological materials (such as tissues and cells) as well as in man-made materials (such as paper and textiles). Resistance to external forces is a key property of these materials. Still, it is not understood how the mechanical characteristics of the fibers and the distribution of the cross-links between fibers determine the stiffness of the entire network. Here, fibrous networks with precise control over network architecture will be created. These materials will then be tested mechanically. Thereby, this research will reveal exactly which microscopic parameters matter most in defining network stiffness. Specific results will test a recent predictive model of network mechanics and contribute to the fundamental understanding of the mechanical properties of biomaterials. General outcomes will influence the use of artificial fibrous materials, with potential impacts for the design of prosthetics and/or tissue implants. The Principal Investigators will contribute to human resource development in Science, Technology, Math and Engineering. The investigators will synthesize fibrous networks using sequence-based self-assembly of DNA, and test their mechanical properties using an array of methods of rheology. Networks will be designed using a two-component strategy in which linkers are attached to multi-armed nodes. As a result, it will be possible to independently vary the bend stiffness and stretch stiffness of the linkers, as well as the connectivity of the nodes. Investigation will focus on so-called "marginal gels" (i.e. networks whose connectivity is in the vicinity of the Maxwell isostatic point) that are predicted to have dramatic mechanical properties associated with thermodynamic critical behavior, including a sudden stiffening with connectivity, and critical fluctuations. College internship opportunities and through cross-disciplinary graduate student training will be provided. International collaboration via student exchanges and through an international summer workshop on biomolecular networks will be conducted.