Just add warm water, and a specially designed polymer composite can fold into a box or even a flower — on its own.
The material, a hydrogel embedded with carbon nanotubes, was conceived by Ali Javey at the University of California, Berkeley, and his collaborators. At room temperature, the composite is hydrophilic and water is incorporated in its structure. But above a threshold temperature of around 33 °C, it becomes hydrophobic and extrudes water. This reversible transition causes a mechanical strain that can be exploited to create shape-changing actuators. The carbon nanotubes ensure a fast response time.
In 48 °C water, the material took 35 seconds to fold into a box (pictured). Such fast self-folding materials could be useful for applications including smart solar devices and tissue engineering.
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Shape-shifter forms box in water. Nature 475, 426 (2011). https://doi.org/10.1038/475426c
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DOI: https://doi.org/10.1038/475426c
