Last October, scientists at MIT had demonstrated that graphene could be “crumpled” and then flattened again without losing efficiency in the electrodes of supercapacitators that could be used to power flexible electronics.
Now, researchers at the University of Illinois have come up with a novel, single-step method to achieve three-dimensional (3D) texturing of graphene and graphite. The newly-discovered technique, called “crumpling”, allows for larger surface areas and opens the door to expanded capabilities for 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.
His team believes the “crumpled” graphene surfaces could be used as higher surface area electrodes for battery and supercapacitor applications. As a coating layer, the 3D textured 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 – a “smart” polymeric material capable of returning from a deformed state to its original shape induced by heat or some other external trigger.
While graphene intrinsically exhibits tiny ripples in ambient conditions, the researchers created large and tuneable “crumpled” textures in a tailored and scalable fashion, which the previous techniques did not allow.
“As a simpler, more scalable, and spatially selective method, this texturing of graphene and graphite exploits the thermally induced transformation of shape-memory thermoplastics, which has been previously applied to microfluidic device fabrication, metallic film patterning, nano-wire assembly, and robotic self-assembly applications,” said Nam.
The thermoplastic nature of the polymeric substrate also allows for the “crumpled” graphene morphology to be arbitrarily re-flattened at the same elevated temperature for the “crumpling” process.
“Due to the extremely low cost and ease of processing of our approach, we believe that this will be a new way to manufacture nano-scale topographies for graphene and many other 2D and thin-film materials.”
In continuing their 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.”
The findings have been published in the journal Nano Letters.