MANHASSET, NY The International Electron Devices Meeting this December will highlight developments in power research.
While Japanese researchers report on a power transmisson sheet, a team from Cornell University will describe development of a radioisotope-based, CMOS-compatible piezoelectric aluminum-nitride (AlN) power generator. They claim the device could power a wireless sensor node for decades.
The Cornell presentation at IEDM will describe one of the first implementations of AlN radioisotope power generators. It represents a new level of integration for microelectromechanical systems (MEMS) and CMOS-compatible power generators, according the researchers.
The AlN generator includes three output ports to power a wireless sensor node. The generator also demonstrated that radioactive thin-films based on nickel isotopes (Ni-63) can be safely used to power a wireless sensor node, the researchers said.
The Cornell team limited itself to Ni-63 for research purposes. Integrating higher-power density radioactive films such as promethium-147 or tritium could provide a thousand-fold improvement in power output, they claimed.
The thin film of the radioisotope Ni-63 produces beta particles used to generate electricity. The particles strike a cantilever made from an AlN compound. After charge separation, charge accumulates and electrostatic attraction pulls the cantilever toward the Ni-63 film. After contact, the charge dissipates and the cantilever returns to its original position. The cycle is repeated and oscillation of the cantilever continues. Because piezoelectric materials such as AlN generate voltage when they are subjected to mechanical stress, this oscillation produces a continuous voltage.
The generator could also provide power in another way. In operation, beta particles also strike a silicon collector cell. Similar to photovoltaics, where the interplay of sunlight with the p-n junctions in solar cells generates voltage, so-called betavoltaics occur as the beta particles interact with silicon p-n junctions. The result is greater total energy efficiency.
The Cornell researchers claim their generator can power microsystems over a wide temperature range for several decades without refueling. They cited high energy density (about 105 kJ/m3) and the Ni-63 radioisotope's long half-life (100.2 years).
Also at IEDM, University of Tokyo researchers will report on development of a power transmission sheet that selectively supplies power to electronic devices placed on the sheet.
The 1-mm-thick flexible sheet weighs 50 grams and contains an array of 8-by-8 cells containing both position-sensing and -transmission units. The effective power transmission area is 21 by 21 cm2.
|University of Tokyo's power sheet|
An object's position on the sheet is sensed by electromagnetic coupling that uses an organic, active-transistor matrix. Power is fed to devices by an array of copper coils driven by a printed plastic MEMS-switching matrix. Power transmission only occurs when an object is sensed, yielding a net power-coupling efficiency of 62.3 percent.
The Japanese researchers said power levels as high as 29.3 W were transferred using their technique.
They said the sheet could be installed on walls, ceilings or in other locations, creating new options for powering electronic products.