What do rabbits with LEDs in their contact lenses and low-cost fuel cells have in common?
Posted by Marko Spasenovic on June 10, 2013 2 Comments
The diverse beauty of graphene is coming to light through advanced applications as varied as fuel cells and light-emitting contact lenses.
Researchers from Ulsan National Institute of Science & Technology (UNIST) in Korea feature in both these recent achievements which caused much excitement in the graphene community. Graphene has been used as an electrode for fuel cells before, however the most recent demonstration is impressive in its performance and ease of manufacturing. A UNIST team led by Profs. Jong-Beam Baek and Noejung Park ball-milled commercial graphene nanoplatelets in the presence of various halogen elements, such as chlorine, bromine, or iodine. The milling separated the graphene sheets from each other at the edges of the nanoplatelet (nanoplatelets usually consist of multiple graphene sheets) and the halogen material creeped in between the graphene sheets. The result was a compound that acts as an excellent cathode for fuel cells, with better long-term stability than commercially available electrodes.
The same institute published a NanoLetter last week, from the team led by Jang-Ung Park, describing the making of a light-emitting diode (LED) fitted with a transparent electrode made of graphene and metal nanowires. The nanowires serve to connect patches of graphene that are often present in CVD grown graphene, thus improving its electrical conductivity. The hybrid material retains graphene's superb mechanical flexibility and strength, which was forcefully demonstrated by fitting the LED into a contact lens. The lens was placed into the eye of a rabbit, who wore it for five hours without any adverse effects. This research presents a breakthrough in wearable graphene devices, raising hopes that graphene will soon be closer to us than we ever would have thought.
The very same cracks and patches in graphene were previously theoretically predicted to severely reduce the mechanical strength of graphene, however researchers from Columbia saved the day by experimentally proving that graphene retains its amazing strength even with cracks and patches, which are naturally formed during growth. It seems that the culprit for the earlier observed weakness lay in the process of transfer from the copper growth substrate to another one. The Columbia team, led by Prof. James Hone, developed a more gentle graphene transfer procedure and published their paper in Science.
Again from East Asia comes an awesome demonstration of the abilities of graphene, this time in the field of photosensors. Researchers at Nanyang Technological University have shown a graphene photosensor which is 1000 times more sensitive than current imaging sensors used in cameras. That means that with such a sensor we would never need to use a camera flash again!
To end a summary of the past weeks' exciting discoveries, Wired magazine published a guide to making your own graphene. For high quality and large areas, we still recommend buying your graphene from Graphenea.