Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session V53: Extraordinary Mechanical Properties of Bio-inspired Soft MaterialsInvited
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Sponsoring Units: GSOFT Chair: Wouter Ellenbroek, Eindhoven University of Technology Room: BCEC 253C |
Thursday, March 7, 2019 2:30PM - 3:06PM |
V53.00001: Do bio-inspired metal-coordination crosslink dynamics offer anything new for engineers of hydrogel mechanics? Invited Speaker: Niels Holten-Andersen Efforts to engineer synthetic polymer hydrogel mechanics is increasingly coupled to the design of transient crosslink dynamics. Based on the growing evidence supporting a critical role in desirable material applications in nature, bio-inspired metal-coordinate transient crosslinking might provide unique opportunities in these efforts. Using simple metal-coordinating polymers, we have sought to gain a deeper understanding of whether polymer hydrogel mechanical properties can be controlled over multiple hierarchical time-scales via design of metal-coordinate crosslink structure on multiple length-scales. Specifically, by utilizing metal ion-coordination complexes and metal nanoparticle-coordination junctions as supra-molecular crosslink structures, we have obtained easy access to control over network dynamics on the microscopic scale, and thereby unique opportunities to broadly shape the distribution of network stress relaxation on the macroscopic scale. Our findings suggest that bio-inspired metal-coordination crosslink dynamics can indeed be utilized to engineer complex gel mechanics directly via simple design of supramolecular crosslink structure, and could help improve our understanding of and control over spatio-temporal molecular hierarchy in loadbearing biological and bio-inspired materials. |
Thursday, March 7, 2019 3:06PM - 3:42PM |
V53.00002: Flex your mussels: Harnessing nature's designs to build next-generation materials Invited Speaker: Megan T. Valentine Marine mussels create an array of adhesive contacts (the byssus) to secure themselves to rocks, wood, metals and other mussels in the harsh conditions of the intertidal zone. Their superb mechanical and adhesive performance has served as inspiration to create mussel-inspired materials for a wide range of applications ranging from surgical glues to primers and coatings. Historically, much of this success has relied on mimicry of the molecular properties of the mussel's adhesive interfacial proteins. By contrast, the translation of the meso- to macro-scale properties of the natural materials has been comparatively unexplored, providing rich opportunities for further property enhancement to create tough, durable, load-bearing materials. Here, I will present my laboratory's recent work characterizing the properties of natural mussel byssal plaques, and translating these discoveries to enable the design and manufacture of new materials. Experimentally, we observe the dynamics of mussel plaques as they debond from glass using a custom built load frame with integrated dual view imaging capabilities, under monotonic and cyclic loading. We pair these mechanical tests with ultrastructural analysis to understand the molecular origins of strength and toughness. Using insights from the natural materials, we then create high-performance synthetic materials that are extremely strong without compromising extensibility, as well as mussel-inspired 3D structures with tunable stiffness and strength. These innovations open new possibilities for applications of mussel-inspired materials in packaging, soft robotics, and connective tissue repair, and demonstrate the importance of understanding the multiscale, multiphase properties of biological materials. |
Thursday, March 7, 2019 3:42PM - 4:18PM |
V53.00003: Mechanical stresses control the size, shape, and location of phase-separated liquid droplets in polymer networks Invited Speaker: Eric Dufresne Spontaneous phase separation has recently emerged as an essential driver of cytoplasmic organization. With experiments in synthetic materials and living cells, we demonstrate that elastic stresses in polymer networks can regulate phase separation. We apply these insights to the design of photonic materials. |
Thursday, March 7, 2019 4:18PM - 4:54PM |
V53.00004: DNA-directed hydrogel deformation Invited Speaker: Rebecca Schulman DNA polymerization reactions within DNA-crosslinked hydrogels can direct the dramatic shape change of DNA-crosslinked hydrogels, leading of up to 100-fold changes in gel volume. The well-understood kinetics |
Thursday, March 7, 2019 4:54PM - 5:30PM |
V53.00005: How to toughen polymer gels with entropy-mediated reversible crosslinking Invited Speaker: Nicholas Tito Materials composed of polymers that are permanently crosslinked into a network, such as gels and rubbers, eventually break if strained enough. This is because the network irreversibly ruptures once the local forces acting on the polymers and crosslinks become too large for the bonds to withstand. Recent experiments have revealed that adding *reversible* crosslinks to a gel allows it to be strained to a much larger extent, yet without altering its small-strain elasticity [1]. We are using theory, molecular simulation, and polymer self-consistent field theory for networks, to explore reversible crosslinking as a design paradigm for creating polymer materials that are tough but elastic [2]. Emphasis will be placed on how entropy itself drives reversible crosslinks to toughen the material, while preserving its intrinsic elasticity. Practical guidelines will be outlined to optimise this design in experiment, along with a discussion of key kinetic and timescale considerations. |
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