Tiny new antennas could create 'undetectable' surveillance bugs

Ultra-compact antennas could create a new wave of virtually “undetectable” surveillance bugs, an expert has said.

A team of engineers at Northeastern University in Boston in the US created the antennas, which are roughly 100 times smaller than existing examples. They could have a “great impact” on wearable electronics and biological implants, the scientists said, enabling smaller, more efficient devices. The mini-antennas could also enable tiny new Internet of Things (IoT) devices.

Typical antennas pick up signals by resonating with electromagnetic waves and converting them into electricity. The devices have to be roughly one-tenth the length of the wavelengths they are receiving – about 1.25cm for a WiFi wavelength of 12.5cm.

“A lot of people have tried hard to reduce the size of antennas,” said engineer Nian Sun to News @ Northeastern. “We looked into this problem and thought, ‘Why don’t we use a new mechanism?’.”

To overcome the size problem, the Boston team decided to utilise shorter-wavelength acoustic resonance – the same vibrations as sound. The mini-antennas use sheets of material called “piezoelectric thin-film heterostructures”, which expand and contract in magnetic fields. When picking up a signal, the sheets vibrate and convert the signal into voltage.

The use of acoustic resonance allowed the team to create antennas with a diameter of just 200µm – only 0.2mm, much smaller than current state-of-the-art examples.

“They are more mobile and more versatile… that can be a big advantage,” said University College London engineering professor Hugh Griffiths to Professional Engineering. “They can be covert – which is of course very interesting for military or security-type applications… bugs and things like that.”

The new antennas could be virtually undetectable, said Griffiths, who was not involved in the research. Although they would radiate signals, he said they are so small it would still be incredibly difficult to find them.

“I suppose the only questions are how difficult and costly it is to fabricate these things and that is probably something that will take time, many years, to sort out – but just knowing it is possible is very exciting,” said Griffiths.

The research was published in Nature.