Engineers from Donghua University in Shanghai have developed a graphene-based paper that can walk and fold itself. Inspired by origami, the nanostructure can be excited by light or heat to change shapes, walk or turn around a corner. The study, published in Science Advances, could find applications in robotics, sensing and the creation of artificial muscles.
Origami has influenced research in many disciplines, from robotics to tissue engineering: self-folding devices can move without external forces being applied. For that to happen, the materials used must have the property of transforming energy into mechanical work. So far, self-folding structures have been created from different polymers that respond to environmental cues like pH, temperature or light. However, these studies are just proofs of concept without practical application.
Meifang Zhu and her team were impressed by a research paper that predicted the use of graphene nanocages as self-folding devices. The use of graphene as material for robotics would be an improvement over polymers, as it is stronger and more versatile. Graphene nanosheets have already been used as building blocks, and macroscopic graphene materials could be used to build elastic and flexible macrostructures that respond to light, absorbing its energy and transforming it into mechanical work. However, macroscale graphene origami has not been developed yet.
Graphene lines absorb and loss water to move
With this project, Meifang Zhu’s team has pioneered the development of macroscale origami, designing a graphene-based structure made from nanoscale building blocks. The researchers constructed a self-folding graphene paper that can be remote-controlled with heat or light to make it change its shape, walk or turn a corner. The motions are previously designed by creating a pattern of graphene oxide-polydopamine (GO-PDA) lines on a supporting graphene layer: the lines can absorb water, thus expanding the structure, and shrink it by water loss upon irradiation. The high photothermal conversion efficiency and flexibility of the supporting graphene is also important for the device to function properly.
This study will allow future uses of graphene as a construction material for large-scale, self-folding devices in robotics.
Source: Donghua University