Ultralow power transistors could function for years without a battery

A newly-developed form of transistor opens up a range of new electronic applications including wearable or implantable devices by drastically reducing the amount of power used. Devices based on this type of ultralow power transistor, developed by engineers at the University of Cambridge, could function for months or even years without a battery by 'scavenging' energy from their environment.

Using a similar principle to a computer in sleep mode, the new transistor harnesses a tiny 'leakage' of electrical current, known as a near-off-state current, for its operations. This leak, like water dripping from a faulty tap, is a characteristic of all transistors, but this is the first time that it has been effectively captured and used functionally. The results, reported in the journal Science, open up new avenues for system design for the Internet of Things, in which most of the things we interact with every day are connected to the Internet.

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, a so-called 'Schottky barrier.'

"We're challenging conventional perception of how a transistor should be," said Professor Arokia Nathan of Cambridge's Department of Engineering, the paper's co-author. "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."

The new design gets around one of the main issues preventing the development of ultralow power transistors, namely the ability to produce them at very small sizes. As transistors get smaller, their two electrodes start to influence the behaviour of one another, and the voltages spread, meaning that below a certain size, transistors fail to function as desired. By changing the design of the transistors, the Cambridge 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 very 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. This ultralow power consumption makes them most suitable for applications where function is more important than speed, which is the essence of the Internet of Things.

"If we were to draw energy from a typical AA battery based on this design, it would last for a billion years," said Dr Sungsik Lee, the paper's first author, also from the Department of Engineering. "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."

"This will bring about a new design model for ultralow power sensor interfaces and analogue signal processing in wearable and , all of which are critical for the Internet of Things," said Nathan.

"This is an ingenious transistor concept," said Professor Gehan Amaratunga, Head of the Electronics, Power and Energy Conversion Group at Cambridge's Engineering Department. "This type of ultra-low power operation is a pre-requisite for many of the new ubiquitous electronics applications, where what matters is function - in essence 'intelligence' - without the demand for speed. In such applications the possibility of having totally autonomous electronics now becomes a possibility. The system can rely on harvesting background energy from the environment for very long term operation, which is akin to organisms such as bacteria in biology."


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More information: "Subthreshold Schottky-barrier thin-film transistors with ultralow power and high intrinsic gain" science.sciencemag.org/cgi/doi … 1126/science.aah5035
Journal information: Science

Citation: Ultralow power transistors could function for years without a battery (2016, October 20) retrieved 19 May 2019 from https://phys.org/news/2016-10-ultralow-power-transistors-function-years.html
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Oct 20, 2016
This could also be useful for deep space missions, depending on operating temperature thresholds.

Oct 20, 2016
"If we were to draw energy from a typical AA battery based on this design, it would last for a billion years,"


Not quite. A billionth of a watt for a billion years is 1 Watt-year and AA batteries don't have that much. They have about 1 Watt-hour which would make the battery last about 100,000 years.

So a few orders of magnitude off, but still impressive. Of course that's just a single transistor, and even a simple digital circuit with any sort of CPU in it will have thousands or millions of them, so you could plausibly make a thing that runs a few decades on an AA battery.

Or practically, about 10 years which is the shelf-life of a typical alkaline battery. You still have to swap batteries out of all the IoT gadgets and doodads, but that's alright because the cloud servers that are supporting them go dark about every 5-6 years from planned obsolescence.

Oct 20, 2016
Grand Announcements in Technology Template:

1. State the "discovery"
2. Put in some information that really tells you nothing.
3. State that it's a great thing that's coming.
4. Provide no delivery date, even a rough one.
5. Never, EVER deliver the product!

Oct 21, 2016
Grand Announcements in Technology Template:

1. State the "discovery"
2. Put in some information that really tells you nothing.
3. State that it's a great thing that's coming.
4. Provide no delivery date, even a rough one.
5. Never, EVER deliver the product!


You don't seem to understand how the scientific method works...

Oct 21, 2016
@rrrander
this is just a sneak peek, real application usually take around 30 years to realize. For example; lets take neuro-implant technology as an example; the first demonstration of retina implant was tested around 1970s, but the real commercial application, such as a Cochlear implant, happen only after year 2000s. That is 30 year gap.

It could be quicker today, I don't know.

Oct 22, 2016
It could be quicker today, I don't know.


Usually in material sciences, the practical applications follow immediately once someone figures out how to mass-manufacture the thing.

However, if the only application you could think of for an ultra-low-power and ultra slow transistor is in IoT then attaching the world "practical" to "application" is an oxymoron.

Oct 23, 2016
This comment has been removed by a moderator.

Oct 23, 2016
Grand Announcements in Technology Template:

1. State the "discovery"
2. Put in some information that really tells you nothing.
3. State that it's a great thing that's coming.
4. Provide no delivery date, even a rough one.
5. Never, EVER deliver the product!


You don't seem to understand how the scientific method works...


1. Promise the moon.
2. Get funded, by universities or the state.
3. Never get the product to market.
4. But we learned so much from the research!
5. You kept your pointless job going for a long time.

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