Posted by Charles Manry
Tiny but powerful capacitors (aka microsupercapacitors) could make cheaper and tiny electronics like cell phones, cardiac pacemakers, and even desktop computers. They’d be great in nonvolatile memory, microsensors and actuators, RFID tags, and microelectromechanical systems, applications in which the power supplies can weigh up to 10 times as much as all the other parts combined.
Tiny versions of capacitors, like all such devices, would be able to release their charge very rapidly. Thus they could be coupled with high-energy batteries to provide periodic surges, as conventional capacitors do today to power such power hungry but short time duration events such as the flash in smartphone cameras. In this example miniaturized supercapacitors could thus lead to even thinner smartphones.
A group at the University of California, Los Angeles, has created such microsupercapacitors using a simple DVD burner to forge the one-atom- thick sheets known as graphene on which these devices are formed, in arrays. Together with a battery, such supercapacitors could run a cellphone for days. And because an array is less than 10 micrometers thick—far finer than a human hair—it is completely flexible. Build these arrays on flexible substrates and they could power a roll-up display. Very importantly it can done at low cost.
Their fabrication method can easily be scaled up, and our microsupercapacitors can be readily integrated onto silicon chips. In many cases they can make up for the inherent weaknesses of batteries, such as relatively slow power delivery and long recharge times. So even in those applications where these devices cannot replace batteries, they will augment them enormously.
The result is a marvelously compact battery and power supplies that can be integrated directly with silicon circuitry. By contrast, today’s computer motherboards require complex interconnects between the electronics and the backup power supply, typically a coin-size lithium battery that keeps memory alive when system power is off. Because these microsupercapacitors can be integrated on-chip it could make it easier to extract energy from mechanical, thermal, and solar sources. For instance, they could be fabricated on the backs—literally—of solar cells to store power generated during the day for use after sundown. Typical practice today is to use batteries for this application, but supercapacitors would be better because they can extract charge much more efficiently and with minimal losses. In addition, integrated supercapacitors can simplify the external wiring used in conventional energy harvesting and storage systems.