Thin-film chemical origami

Can the same mechanisms that shape flower petals into intricate 3-D structures be replicated with artificial materials? Physicist Eran Sharon and colleagues at Hebrew University of Jerusalem shed light on such wonders of natural development by orchestrating crumples and folds in planar thin films (Science 2007, 315, 1116). The researchers created sheets of N-isopropylacrylamide gels cross-linked with bisacrylamide and specifically manipulated monomer concentrations before polymerization. At 33 °C, the areas of the different sheets with dilute monomer concentrations shrank dramatically to create cylinders, waves (one shown), and even sombrero shapes. The researchers suggest guidelines for how to create each shape. In a related commentary, physicist Randall D. Kamien of the University of Pennsylvania calls the work "better geometry through chemistry," and he relates the phenomenon to the process that sculpts potato chips into their familiar final shapes. Sharon and his coworkers plan to further investigate how light, glucose, and other chemical signals can be used to control their self-folding polymer films.