Last October, researchers at MIT showed that graphene could be crumpled and then flattened again and still remain effective for use in the electrodes of supercapacitors that could be used to power flexible electronics.
Now a team at the University of Illinois at Urbana-Champaign are showing that if you keep the graphene crumpled, you increase its surface area. This 3D surfaced graphene could open new application areas for the material in electronics and biomaterials.
“Fundamentally, intrinsic strains on crumpled graphene could allow modulation of electrical and optical properties of graphene,” explained SungWoo Nam, an assistant professor of mechanical science and engineering at Illinois, in a press release. “We believe that the crumpled graphene surfaces can be used as higher surface area electrodes for battery and supercapacitor applications. As a coating layer, 3D textured/crumpled nano-topographies could allow omniphobic/anti-bacterial surfaces for advanced coating applications.”
To achieve their crumpled graphene, the researchers developed a one-stop process that draws upon a commercially available shape-memory polymer substrate that is activated by heat.
The researchers report in the journal Nano Letters that their method allows them to selectively pattern the crumples, which was not possible with other techniques.
“In this study, we developed a novel method for controlled crumpling of graphene and graphite via heat-induced contractile deformation of the underlying substrate,” said Michael Cai Wang, a graduate student and first author of the paper, in the release. ”While graphene intrinsically exhibits tiny ripples in ambient conditions, we created large and tunable crumpled textures in a tailored and scalable fashion.”
Shape-memory thermoplastics have been applied in microfluidic device fabrication and nanowire assembly among other manufacturing processes. And, of course, the thermoplastic substrate makes it possible to flatten the material again by simply applying heat.
In continuing work, the researchers are looking at how the textured graphene surfaces could be applied to 3D sensor applications.
Nam added: “Enhanced surface area will allow even more sensitive and intimate interactions with biological systems, leading to high sensitivity devices.”