Flip the switch

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How tiny vibrations in minute metal structures – and a little bit of luck – helped make mobile phones faster and more efficient.Research from Professor Charles Smith at Cambridge’s Cavendish Laboratory led to the formation of spin-out company Cavendish Kinetics and the development of digital variable capacitors for mobile phones.
The technology, used in more than 35 million phones, increases the speed at which data can be sent and received.
It also reduces the power required to send and receive signals, increasing efficiency by 100% versus broadband antennas; and significantly reduces CO2 emissions by an estimated 2 million Kg of CO2 emissions per year.

Between 2014 and 2019, the company had a total turnover of $17 million, and employed 52 people. The company was acquired by Qorvo Inc in 2019 for $300 million.

Good vibrations

Fundamental, curiosity-led research often ends up in a place that you didn’t expect. As a PhD student at the Cavendish Laboratory, Professor Charles Smith worked on developing tiny, freestanding metal structures to study the behaviour of phonons – lattice vibrations that carry heat through insulators.

In the decades since, those little metal structures led to the realisation that they could be used to make tiny switches, which resulted in the formation of a spin-out company, which helped make the phones in our pockets faster and more efficient.

“During my PhD, I developed these tiny little devices, about 10 to 50 nanometres wide and 10 nanometres thick,” said Smith. “We found that if you cooled the substrate way down, the phonons freeze out across the wire and become a one-dimensional thermal conductivity system.”

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At the same time, other researchers were working on the development and improvement of micro-electrical mechanical switches, or MEMS.

“After my PhD, I realised that these two things together, the freestanding wires and MEMS, could have a lot of potential uses as tiny low voltage switches,” said Smith. “The switches could also be made into memory devices. This was quite similar to flash memory, but our approach used far less power: just a few volts, compared to flash. memory which used tens of volts.”

After carrying out a series of experiments to test his idea, Smith decided to form a company, Cavendish Kinetics, in 1994.

By Sarah Collins

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