Shape shifter

Researchers in Israel have programmed polymer sheets to bend and wrinkle by themselves into prescribed structures.


Dr. Eran Sharon and his co-workers, Yael Klein and Efi Efrati, at the Hebrew University of Jerusalem Racah Institute of Physics, have succeeded in programming polymer sheets to bend and wrinkle by themselves into prescribed structures.


They made flat discs of a soft gel that, when warmed gently, curved into domes, saddles and even sombrero shapes.


The sheets change shape because the gel – a web of cross-linked polymers – shrinks at temperatures above 33oC by an amount determined by the local polymer density.


When the density varies across the disc, the sheet buckles to relieve the pressure of uneven shrinkage.


The researchers worked out what shrinkage patterns would produce the structures they wanted, and then used an automated mixing system to produce “cocktails” of gels with the right properties.


Such switchable shape control in a soft material could have applications ranging from optics to biomedicine.


‘Our work enables the creation of highly complex structures, which sometimes would be difficult to manufacture through regular industrial means,’ said Dr Sharon. ‘Additionally, such research provides greater understanding of the ways in which complex structures, such as flowers, develop in nature’, he added.