Interscatter’ tech lets implants talk Wi-Fi

August 22, 2016 // By Junko Yoshida
University of Washington researchers have developed what they call “interscatter communication” technology that backscatters (or reflects) existing signals like Bluetooth in the air, transforming wireless transmissions from one technology to another.

Specifically, the team of UW electrical engineers and computer scientists has demonstrated for the first time that Bluetooth transmissions can be used to create Wi-Fi and ZigBee-compatible signals.

As a result, the new technology can now give power-constrained devices like medical implants the ability to “talk” to other devices using standard Wi-Fi communication.

‘Recycle’ radio signals
Picture tiny devices such as smart contact lenses, brain implants or credit cards, said Vikram Iyer, a UW electrical engineering doctoral student who co-authored the paper. “They can’t use Bluetooth or Wi-Fi chips because they consume too much power in generating their own radio signals.”

Enter the world of “interscatter communication.”

Instead of generating their own radio signals, those “interscatter” devices can “recycle” radio signals transmitted by nearby devices like smart watches.

“We allow a device like a smartwatch or smartphone to do the power expensive generation of radio signals, and then our low-power contact lens, implant or credit card reflects this signal in a way that encodes its own data,” he explained. The transmitter of such interscatter devices isn’t a normal radio. It’s just a switch connected to an antenna, Iyer added.

“Turning on and off this switch allows us to change how the antenna reflects energy. Just by turning on and off this switch at the right rate, our interscatter device is reflecting a Bluetooth signal created by something like a smartwatch to make it look like a Wi-Fi packet that can be received on your phone.”

“Interscatter” communication generates low-power Wi-Fi transmissions using everyday mobile devices. In one example, Bluetooth signals from a smartwatch (left) transmit data from a neural device that can be implanted in a patient’s brain (right) to a smartphone via Wi-FI.(Source: Mark Stone/University of Washington)

In one example, the team demonstrated a smartwatch transmitting a Bluetooth signal to a smart contact lens outfitted with an antenna. To create a blank slate on which new information can be written, the UW team developed a way to transform the Bluetooth transmission into a “single tone” signal that can be further manipulated and transformed.

By backscattering that tone signal, the contact lens can encode data — such as health information it may be collecting — into a standard Wi-Fi packet readable by a smartphone, tablet or laptop.

Preserving battery life is paramount for implanted medical devices. “If you have a radio that quickly drains the battery then you might need surgery to replace it,” said Iyer. “Contact lenses are even more extreme in that their tiny batteries may not even be able to power normal Wi-Fi and Bluetooth chip.”

Interscatter enables Wi-Fi for these implanted devices while “consuming only 10,000x less power than a normal Wi-Fi chip,” he added.