Want your IoT devices to last a billion years? Use an AA battery, or just suck the leakage out of your transistors, according to a new paper in the American Association for the Advancement of Science journal Science, published in the October 21 issue.
The two researchers, Sungsik Lee, Arokia Nathan, are both in the Electrical Engineering Division of the Engineering department of the University of Cambridge in the UK, have designed new ultralow power transistors that, if all goes as described, could function for years without a battery. They operate on ‘scavenged’ energy from their environment, and therefore should be able to power devices for months or years without a battery, and provide enough juice for wearable or implantable electronics.
It uses a principle similar to sleep mode, much like other low-power devices, but adds in the ability to harness electrical near-off-state current for its operations. This energy leakage is apparently common to all transistors, but this is the first time that it has been effectively captured and used functionally, the researchers said.
The transistors can be produced at low temperatures and can be printed on almost any material, from glass and plastic to polyester and paper. They are based on a unique geometry which uses a ‘non-desirable’ characteristic, namely the point of contact between the metal and semiconducting components of a transistor, or the ‘Schottky barrier.’
“We’re challenging conventional perception of how a transistor should be,” said Nathan. “We’ve found that these Schottky barriers, which most engineers try to avoid, actually have the ideal characteristics for the type of ultralow power applications we’re looking at, such as wearable or implantable electronics for health monitoring. This will bring about a new design model for ultralow power sensor interfaces and analogue signal processing in wearable and implantable devices, all of which are critical for the Internet of Things.”
The new design also addresses the issue of scale. As transistors get smaller, the electrodes will start to influence the behavior of one another and the voltages spread, so usually transistors fail to function below a certain size. With this design, the researchers were able to use the Schottky barriers to keep the electrodes independent from one another, so that the transistors can be scaled down to very small geometries.
The design also achieves a high level of gain, or signal amplification. The transistor’s operating voltage is less than a volt, with power consumption below a billionth of a watt.
“If we were to draw energy from a typical AA battery based on this design, it would last for a billion years,” said Lee. “Using the Schottky barrier allows us to keep the electrodes from interfering with each other in order to amplify the amplitude of the signal even at the state where the transistor is almost switched off.”
Sorry Doc, looks like we don’t need your 1.21 gigawatts after all.