The ancient art of origami has been given a modern twist, thanks to a team of scientists at Donghua University in China, who drew inspiration from the Japanese paper-folding technique to convert a sheet of graphene into a walking robot. The sheet can be remote controlled simply by heating or illuminating it, and is even able to turn corners and adopt predesigned shapes.
Researchers now hope that the technology, which represents an improvement on previous folding structures, can be used for a range of purposes, including the creation of artificial muscles.
The adaptation of origami principles for robotics is not a new concept, and has played a pivotal role in the design of several self-folding structures in the past. For instance, a paper published in the journal Science last year explained how a particular fold called the Miura-ori tessellation may be used to provide mechanical stability to some robots.
However, in a new paper in the journal Science Advances, the team from Donghua pointed out that previous attempts to create self-folding structures have tended to use polymers – large molecules made of repeated subunits – which have poor stability. Furthermore, polymer sheets do not expand and shrink evenly, which means they do not fold smoothly, and can only be controlled using wires and circuit connections. Yet by using graphene, the researchers claim to have created a superior structure. Not only is graphene stronger and more nimble than traditional polymers, but the sheet can also be controlled remotely.
Graphene, which consists of layers of hexagonally-arranged carbon atoms just one atom thick, is known for its supreme flexibility, and was once labeled “the strongest material ever measured.” According to James Hone, professor of mechanical engineering at Columbia University, graphene is “200 times stronger than structured steel.”
By lightly altering the humidity, temperature and light around the structure, the team behind the present study found that the graphene sheet readily absorbed and desorbed water molecules, causing it to bend and straighten. As the video below shows, this enabled the sheet to "walk" while being controlled remotely. Researchers believe they have now addressed many of the issues hindering previous self-folding devices, and hope that the implications will be far-reaching within the robotics industry and beyond.