If I learned one thing about concepts and prototypes, I learned that most of them never make it to the production line and with time they are forgotten. However, this is not the case of a prototype device created by researchers at the University of Southern California Viterbi School of Engineering. This device is a supercapacitor who usually performs electronic operations thanks to silicon chips, but the USC researchers managed to develop a transparent and flexible supercapacitor using carbon nanotubes.
The team of researchers led by Chongwu Zhou claims that the supercapacitor which uses CNT films and indium-oxide nanowires can be manufactured at prices competitive with conventional techniques which use silicon. Also, this energy storage and conversion device is completely transparent, and is so flexible that it can be “bent and twisted like a poker card.”
According to Zhou, this new capacitor features an energy density of 1.29 watt-hour per kilogram, and a storage capacitance of 64 Farad per gram, while conventional capacitors store an energy density of at most .1 watt-hour per kilogram with a specific capacitance in the range of tens of millifarads. The team consisting of aforementioned Zhou, USC post-doctorate Guozhen Shen, and USC graduate students Sawalok Sukcharoenchoke and Po-Chiang Chen, believes that their supercapacitor will have enormous implications in e-paper displays, many electronic devices, and other applications.
Zhou and his team attached indium-oxide and CNTs films on a transparent flexible substrate, then they optimized its thickness in order to preserve its flexibility and its transparency. The researchers managed to combine metal nanowires with carbon nanotubes (after many attempts) and they said that this represents the key for flexible and transparent supercapacitors as conventional storage devices are not flexible, neither transparent.
“We demonstrated enhanced specific capacitance, power density, energy density, and long operation cycles, compared to those supercapacitors made only by CNTs,” said Zhou. “We successfully produced a prototype of flexible and transparent supercapacitors built on two important nanostructured materials [including metal oxide nanowires and CNTs].”
“CNT films were fabricated by vacuum filtration method. An adhesive and flat poly (dimethysiloxane) (PDMS) stamp was adapted to peel the CNT film off of the filtration membrane and then released it onto a polyethylene terephtalate (PET) substrate. In2O3 nanowires with a diameter of ~ 20 nm and a length of ~ 5 ?m were synthesized by a pulsed laser deposition (PLD) method. The as-grown nanowires were sonicated into IPA solutions and then dispersed upon transferred CNT films to form In2O3 nanowire /CNT heterogeneous film for transparent and flexible supercapacitor study,” explained Zhou.
Well, as the researchers have demonstrated the potential of flexible and transparent supercapacitors, now we are waiting for the devices to be commercialized. Zhou said that the new supercapacitors can be manufactured at costs competitive with conventional supercapacitors and we can’t understand why the researcher didn’t mention when the devices will be available. We will have to wait for further details.