A Chinese team from Donghua University in Shanghai has designed a graphene-based paper that can move on its own. Like paper, graphene is strong but flexible, so it can be deformed quite easily, but until now, it could not move by itself. Like an origami, the object comes to life, folds and unfolds at will. This work was published in the scientific journal Science Advances.
Ahe shape memory materials already exist, what Joël de Rosnay calls "intelligent material", i.e. it is sensitive, adaptive and evolutionary: "It has functions that allow it to behave like a sensor (detect signals), an actuator (perform an action on its environment) or sometimes like a processor (process, compare, store information). This material is capable of spontaneously changing its physical properties, such as shape, connectivity, viscoelasticity or colour, in response to natural or induced excitations from outside or inside the material. For example, variations in temperature, mechanical stress, electric or magnetic fields. The material will therefore adapt its response. »
(Source: Futura-Sciences.com, 2002)
We are indeed here in the world of intelligent materials, where researchers from Donghua University in China have developed a graphene-based paper that can move on its own.
To achieve this feat, the researchers used graphene, a material discovered in 2004 by two scientists who won the 2010 Nobel Prize in Physics. They have developed two different graphene solutions. This "miracle" material has many properties. For example, it is an excellent conductor of electricity: electrons flow almost 150 times faster on graphene than on silicon, which is now used to manufacture electronic chips. Graphene is also 200 times stronger and six times lighter than steel.
The Chinese researchers were therefore able to create a paper with two layers, the first of graphite oxide and the second of polymerized dopamine and water molecules. When exposed to light or heat, this layer shrinks. The other layer reacts to this action by bending or folding. By using an infrared laser with great precision, researchers were able to develop small pieces of paper that can move on command.
The areas of the paper soaked in both solutions shrink when heated and return to their original position when the heat source is turned off. The paper then literally starts to move.
This impressive innovation could eventually be used to make artificial muscles for robots. But researchers now want to take this technology one step further by looking at graphene nanoparticles. For, compared with steel, prepared graphene paper is six times lighter, five to six times less dense, twice as hard, 10 times more extensible and 13 times more rigid when folded," the researchers explained, adding that the material was also a "sustainable and recyclable product that is both environmentally friendly and cost-effective.
Because of their small size, these microscopic objects will have properties that are even different from those already developed by scientists.