Ultra-thin graphene-based stretchable supercapacitors, which could be used to power soft robots and advanced wearable technologies, have been developed by scientists for the first time.

The research, which was undertaken by scientists at Nanyang Technological University in Singapore, is significant in particular for wearable technology because it resolves the common problem of a rigid, lumpy battery that has to be hidden in fabric folds or seams.

“Most power sources, such as phone batteries, are not stretchable. They are very rigid,” explained research lead Dr Xiaodong Chen, from Nanyang Technological University.

“My team has made stretchable electrodes, and we have integrated them into a supercapacitor, which is an energy storage device that powers electronic gadgets.”

The researchers’ use of graphene was also unprecedented, because although the material has been proposed for use in wearable technologies, it is not known for its ability to stretch.  “Graphene can be flexible and foldable, but it cannot be stretched,” said Chen.

The solution was to mimic human skin, which has a wave -like microstructure that allows it to stretch as needed. “We started to think of how we could make graphene more like a wave,” added Chen.

The solution was to make graphene micro-ribbons using a chemical construction method, rather than the physical ‘shaving’ approach typically used to make graphene sheets.

“We have more control over the graphene’s structure and thickness that way,” he said. “It’s very difficult to control that with the physical approach. Thickness can really affect the conductivity of the electrodes and how much energy the supercapacitor overall can hold.”

The resulting ribbon was affixed to a stretchable polymer chip that had a series of pyramid-like ridges built into it. By placing the graphene ribbon in a wave-like formation across the ridges, the scientists were able to make it stretch without breaking or deforming.  The result was a stretchy micro-supercapacitor that could be used to power small-scale electronics or act as a pressure or chemical sensor.

The scientists were able to further increase the supercapacitors’ flexibility by introducing origami-like kirigami structures into the design, increasing flexibility by 500% without reducing electrical performance.

While the technology is still in the early stages of development, it has tremendous potential for both robotics and wearables. As a result, the researchers are continuing their work to refine the technology.

At present, the supercapacitor can only power the equivalent of an LCD in a calculator for just one minute, but the team is planning to significantly increase this in the future. Chen plans to boost the surface area of the supercapacitor’s electrode, which would allow it to hold more energy.

The research will be presented today at the 252nd National Meeting & Exposition of the American Chemical Society (ACS).