When someone crumples a sheet of paper, that typically means it is about to be thrown away. However, researchers have now found that crumpling a piece of Graphene "paper", which can actually yield new properties that could be useful for creating extremely stretchable super-capacitors to store energy for flexible electronic devices.
The findings are reported in the journal of Scientific Reports by MIT's Xuanhe Zhao, the Brit (1961) and Alex (1949) d'Arbeloff Career Development Associate Professor in Engineering Design and four other authors. It is claimed it is novel, flexible super-capacitors and should be easy and inexpensive to nano-fabricate.
As stated by Zhao - "Many people are exploring Graphene paper: It's a good candidate for making super-capacitors, because of its large surface area per mass,". Also, he states, the development of flexible electronic devices, such as wearable or implantable biomedical sensors as well as monitoring devices, which will require flexible power-storage systems.
Similar to batteries - super-capacitors can store electrical energy, but they primarily do so electrostatically, rather than chemically, thus, meaning they can deliver their energy faster than batteries can. At the moment Zhao et al. has managed to demonstrate that by crumpling a sheet of Graphene paper into a chaotic mass of folds, that they can make a super-capacitor that can easily be bent, folded or stretched to as much as 800% of its original size. Essentially the team has made a simple super-capacitor employing this method as a Proof-of-Principle.
The team has managed to demonstrate, that a material can be crumpled and flattened up to 1,000 times without a significant loss of performance. Zhao continues to state - "The Graphene paper is pretty robust," - "and we can achieve very large deformation over multiple cycles." As historically known - Graphene, is a structure of pure Carbon (C) just one atom thick with its C atoms arranged in a hexagonal array and is known as one of the strongest materials.
To fabricate the crumpled Graphene paper, a sheet of the material was placed in a mechanical device that first compressed it in one direction, creating a series of parallel folds or pleats, and then in other direction, leading to a chaotic, rumpled surface. When stretched, the material's folds simply smooth themselves out.
Forming a capacitor requires two conductive layers, and in this case, two sheets of crumpled Graphene paper, with an insulting layer in between, which in this demonstration was made from a hydrogel material. Similar to the crumpled Graphene, the hydrogel is highly deformable and stretchable, so the three layers remain in contact even while being flexed and pulled.
Zhao adds - "Though this initial demonstration was specifically to make a super-capacitor, the same crumpling technique could be applied to other uses" - for example, the crumpled Graphene material might be usable as one electrode in a flexible battery, or could be used to make a stretchable sensor for specific chemical and/or biological molecules.
Another researcher involved - Dan Li, Professor of Materials Engineering at Monash University in Australia - stated - "This work is really exciting and amazing to me." In addition, he adds that the team "provides an extremely simple but highly effective concept to make stretchable electrodes for super-capacitors by controlled crumpling of multi-layered Graphene films." While it is conceded other groups have made flexible super-capacitors, he states - "Making super-capacitors stretchable has been a great challenge. The paper provides a very smart way to tackle this challenge, which I believe will bring wearable energy storage devices closer."
Please Note the research team included other contributors, such as Jianfeng Zang at Huazhong University of Science and Technology and Changyang Cao, Yaying Feng and Jie Liu at Duke University. Plus, this research was supported by the Office of Naval Research, the National Science Foundation and the National 1000 Talents Program of China. Original article available here
The above research continues to positively highlight the potential of Graphene sensors and/or flexible substrates. As stated previously, DCN Corp strongly believes it can compete. Going forward, if you and/or your colleagues are interested in making DCN Corp's alternative process reality - please ensure to contact the company as soon as practicably possible.