The visco-elastic mechanical properties of hydrogel network can be programmed using bio-inspired metal-coordinate crosslinks sensitive to UV light. Depending on the metal ion used to crosslink the hydrogel, the stiffness can be increased by 1000x, decreased by 100x, or remain unchanged by UV-irradiation.
Grindy, Holten-Andersen, Bio-inspired metal-coordinate hydrogels with programmable viscoelastic material functions controlled by longwave UV light, Soft Matter, 2017.
Interactions between polymer molecules and inorganic nanoparticles can play a dominant role in nanocomposite material mechanics, yet control of such interfacial interaction dynamics remains a significant challenge particularly in water. This study presents insights on how to engineer hydrogel material mechanics via nanoparticle interface-controlled cross-link dynamics. Inspired by the adhesive chemistry in mussel threads, we have incorporated iron oxide nanoparticles (Fe3O4 NPs) into a catechol-modified polymer network to obtain hydrogels cross-linked via reversible metal-coordination bonds at Fe3O4 NP surfaces. The structurally controlled hierarchical mechanics presented here suggest how to develop hydrogels with remote-controlled self-healing dynamics.
Li, Barrett, Messersmith, Holten-Andersen, Controlling Hydrogel Mechanics via Bio-Inspired Polymer–Nanoparticle Bond Dynamics, ACS Nano, 2015.
The change from wet and soft to dry and hard is a visco-elastic to solid material transition widely displayed in nature, in particular in materials rich in metal-coordinate cross-linking. How metal-coordinate cross-link dynamics contribute to macromolecular material mechanics upon solidification by dehydration remains an open question. Using mussel-inspired Fe-catechol cross-linked polymer hydrogels, we address this question. In addition to a nearly two-fold increase in stiffness, we find that the presence of Fe-catechol coordination bonds in a dehydrated polymer gel also provides the bulk network with a significantly increased energy dissipation with over three times higher loss factor.
Kim, Peterson, Holten-Andersen, Enhanced Water Retention Maintains Energy Dissipation in Dehydrated Metal-Coordinate Polymer Networks: Another Role for Fe-Catechol Cross-Links?, Chemistry of Materials, 2018.
Samples that show the effect of mixing different lanthanide ions with a ligand material called terpyridine in a solvent. In the top three vials, the lanthanides used are (left to right) lanthanum, europium, and terbium. The fluids display the characteristic colors of those elements. The white-light-emitting fluid in the lower vial was formed by mixing together equal volumes of the blue, red, and green samples above.
Chen, Holten-Andersen, Multistimuli-responsive White Luminescent Fluids Using Hybrid Lanthanide Metal–Coordinate Complex Probes, Advanced Optical Materials, 2015.
Professor Matt Harrington McGill University
Professor Joseph Tracey North Carolina State University
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