Materials Science

Sponges Tough and Soft

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Science  17 Jul 2009:
Vol. 325, Issue 5938, pp. 246
DOI: 10.1126/science.325_246c

A major challenge in designing biologically compatible implants has been achieving the optimal combination of stiffness, porosity, and toughness (resistance to rupture) for any given local environment. Toward this end, Lee et al. used an ionic liquid to condense a dispersion of DNA-coated carbon nanotubes. The ionic liquid efficiently removed bound water from the DNA strands, causing them to form intertwined toroids, which upon drying adopted a porous sponge structure with 50-nm-diameter fibers. The fiber diameter, sponge toughness, and stiffness could be adjusted by soaking the networks in water and then in calcium chloride solution: The calcium ions induced DNA cross-linking. The sponge fibers could then be knotted, braided, and woven into fabric structures. Moreover, the material proved electrically conductive and thus potentially applicable in sensing, energy storage, and mechanical actuation.

Angew. Chem. Int. Ed. 48, 5116 (2009).

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