Power/Performance Bits: June 14

Origami battery

A new disposable battery that folds like an origami ninja star could power biosensors and other small devices for use in challenging field conditions. The researchers, from Binghamton University, previously developed a paper-based origami battery. The first design, shaped like a matchbook, stacked four modules together. The ninja star version, which measures about 2.5 inches wide, boasts increased power and voltage, with eight small batteries connected in series.

“Last time, it was a proof of concept. The power density was in the nanowatt range,” said Seokheun “Sean” Choi, professor at Binghamton. “This time, we increased it to the microwatt range. We can light an LED for about 20 minutes or power other types of biosensors.”

Paper-based biosensors include pregnancy tests and HIV tests. The sensitivity of such tests is limited, Choi said, and a battery like his could allow the use of more sophisticated fluorescent or electrochemical biosensors in developing countries. “Commercially available batteries are too wasteful and expensive for the field,” he said. “Ultimately, I’d like to develop instant, disposable, accessible bio-batteries for use in resource-limited regions.”

(Source: Binghamton University)

The new design folds into a star with one inlet at its center and the electrical contacts at the points of each side. After a few drops of dirty water are placed into the inlet, the device can be opened into a Frisbee-like ring to allow each of the eight fuel cells to work. Each module is a sandwich of five functional layers with its own anode, proton exchange membrane and air-cathode.

The original matchbook-sized battery could be produced for about 5 cents. The new star device is more expensive — roughly 70 cents — in part because it uses not only filter paper but also carbon cloth for the anode as well as copper tape. The team’s next goal is to produce a fully paper-based device that has the power density of the new design and a lower price tag.

Supercapacitor on a chip

VTT Technical Research Centre of Finland developed an efficient small-size energy storage, a micro-supercapacitor, which can be integrated directly inside a silicon microcircuit chip. The high energy and power density of the miniaturized energy storage relies on a new hybrid nanomaterial developed recently at VTT.

The energy and power density of a supercapacitor depends on the surface area and conductivity of the solid electrodes. The team developed a hybrid nanomaterial electrode, which consists of porous silicon coated with a few nanometer thick titanium nitride layer by atomic layer deposition (ALD). This approach leads to a record large conductive surface in a small volume. Inclusion of ionic liquid in a micro channel formed in between two hybrid electrodes results in extremely small and efficient energy storage.

Micro-supercapacitors can be integrated directly with active microelectronic devices to store electrical energy generated by different thermal, light and vibration energy harvesters and to supply the electrical energy when needed.

The researchers integrated the new nanomaterial micro-supercapacitor energy storage directly inside a silicon chip. The demonstrated in-chip supercapacitor technology enables storing energy of as much as 0.2 joule and power generation of 2 watts on a one square centimeter silicon chip. At the same time it leaves the surface of the chip available for active integrated microcircuits and sensors.