I’ve never been any good at origami. Hell, I remember struggling to make a paper aeroplane when I was a kid, and I doubt I would fare much better today. But, thanks to some scientists at Donghua University in China, a new material has been invented that is capable of doing all the folding itself! Albeit into a predetermined shape. Finally! Something appropriate for my level of skill.
Self-folding materials have become a major research topic recently, with the majority of research focussing on “active polymers”. These materials are capable of converting other forms of energy, such as light or heat, into mechanical work. But they are far from seeing practical applications due to their complex production methods, unrealistic operating conditions, or complicated combinations of materials, making them fragile.
This is where this new material enters the picture! Here, the researchers have successfully created a sheet of Graphene Oxide (GO) “paper” that overcomes many of the previously mentioned problems. GO, while not quite as spectacular as pure Graphene, possesses many impressive properties, boasting both incredible strength and integrity. The paper’s self-folding properties are also capable of operating under physiological conditions, making it a prime candidate for future applications.
The material itself consists of a sheet of GO with some areas treated with Polydopamine (PDA). These treated areas act like sponges, absorbing water from the environment and swelling in humid conditions, whereas the rest of the sheet remains fairly inert. Application of heat or infrared light then causes this water to evaporate and the PDA treated areas to shrink and pull on the surrounding material, bending the paper into the designed shape. The researchers also noted the speed of this response, with a single strip of the paper able to fold and unfold in around five seconds.
Now all of that is pretty impressive, but what I find way cooler is what devices they constructed using this material. Through careful placement of the PDA treated areas, the researchers were able to create various self-folding objects, including a self assembling box and an artificial hand able to grasp and hold objects up to five times its own weight!
The most popular of these objects is the walking device shown in the gif at the top of this page. Created from a rectangular sheet of GO paper, this device has three PDA treated bands running across it that get progressively wider from front to back. When infrared light is applied, the bending of these areas causes the sheet to curve into an arch, with the rear of the paper curving to greater degree due to the varying width of the treated bands. When the light is removed, the sheet relaxes and moves forwards, with a fast response time that means five of these steps only take two seconds. You can see a video of this little robot in this Nature article on the same subject.
This technology has many potential applications including robotics, materials for sensors, and artificial muscles. One researcher in particular, Hongzhi Wang, has very high hopes for the future of this material, suggesting that it could be integrated into solar cells to build self folding panels. But, while that potential does exist, the researchers have indicated that there are still improvements to be made, as well as new questions to be answered. These include improving the 1.8% energy conversion efficiency, which remains a limiting factor, and exploring how a reduction in size will affect the properties and performance of the material.
So, while all of this COULD open the way for a new type of effortless origami, I highly doubt that it ever will. At least not any time soon. Not when there are more pressing and important applications. I mean, artificial muscles! That’s something I can’t wait to see.
- Cesare, C. (2015). Light and heat propel bendy graphene crawlers. Nature. http://dx.doi.org/10.1038/nature.2015.18742
- Gent, E. (2015). Self-Folding Minirobots Possible with Origami-Inspired Graphene. LiveScience.com. Retrieved 13 November 2015, from http://www.livescience.com/52734-self-folding-graphene-minirobots.html?cmpid=514645
- Matthews, P. (2015). A step forward for graphene walkers | Chemistry World. Rsc.org. Retrieved 13 November 2015, from http://www.rsc.org/chemistryworld/2015/11/graphene-origami-light-self-folding-paper-walking
- Mu, J., Hou, C., Wang, H., Li, Y., Zhang, Q., & Zhu, M. (2015). Origami-inspired active graphene-based paper for programmable instant self-folding walking devices. Science Advances, 1(10), e1500533-e1500533. http://dx.doi.org/10.1126/sciadv.1500533