Widening metal tolerance for hydrogels
Researchers seeking to develop self-healing hydrogels have long sought to mimic the natural ability of mussels to generate strong, flexible threads underwater that allow the mussels to stick to rocks. The natural process that gives these mussel threads, which are called byssal, the ability to break apart and re-form is a purely chemical process, not a biological one, MIT graduate student Seth Cazzell noted in a presentation to the Materials Research Society fall meeting in Boston on Dec. 5. The critical step in the process is the chemical binding of polymer chains to a metal atom (a protein-to-metal bond in the case of the mussel). These links are called cross-linked metal coordination bonds. Their greatest strength occurs when each metal atom binds to three polymer chains, and they form a network that results in a strong hydrogel. In a recently published PNAS paper, Cazzell and associate professor of materials science and engineering Niels Holten-Andersen demonstrated a method...