Helping smart credit cards, implanted medical devices and smart contact lenses achieve Internet connectivity. [Credit: Mark Stone/University of Washington]

Scatter brain implant to communicate with wearable devices

University of Washington engineers have developed a technology that enables devices including brain implants, contact lenses and smaller wearable electronics to talk to devices such as smartphones.

The new ‘interscatter communication’ works by converting Bluetooth signals into Wi-Fi transmissions. Using only reflections, an interscatter device, such as a smart contact lens, converts Bluetooth signals from a smartwatch, for example, into a Wi-Fi signal that can be picked up by a smartphone.

"Wireless connectivity for implanted devices can transform how we manage chronic diseases," said developer Vikram Iyer, a University of Washington electrical engineering doctoral student. "For example, a contact lens could monitor a diabetic’s blood sugar level in tears and send notifications to the phone when the blood sugar level goes down."

Due to their size and location within the body, these smart contact lenses are too constrained by power demands to send data using conventional wireless transmissions. Those same requirements also limit emerging technologies such as brain implants that treat Parkinson's disease, stimulate organs and may one day even reanimate limbs.

The University of Washington team of electrical engineers and computer scientists has demonstrated for the first time that these types of power-limited devices can ‘talk’ to others using standard Wi-Fi communication. Their system requires no specialised equipment, relying solely on mobile devices commonly found with users to generate Wi-Fi signals using 10,000 times less energy than conventional methods.

The team's process relies on a communication technique called backscatter, which allows devices to exchange information simply by reflecting existing signals. Because the new technique enables inter-technology communication by using Bluetooth signals to create Wi-Fi transmissions, the team calls it ‘interscattering’.

Interscatter communication uses the Bluetooth, Wi-Fi or ZigBee radios embedded in common mobile devices like smartphones, watches, laptops, tablets and headsets, to serve as both sources and receivers for these reflected signals.

"Bluetooth devices randomise data transmissions using a process called scrambling," said lead faculty Shyam Gollakota, Assistant Professor of Computer Science and Engineering. "We figured out a way to reverse engineer this scrambling process to send out a single tone signal from Bluetooth-enabled devices, such as smartphones and watches, using a software app."

The challenge, however, is that the backscattering process creates an unwanted mirror image copy of the signal, which consumes more bandwidth as well as interferes with networks on the mirror copy Wi-Fi channel. The University of Washington team developed a technique called ‘single sideband backscatter’ to eliminate this unintended by-product.

Beyond implanted devices, the researchers have also shown that their technology can apply to other applications such as smart credit cards. The team built credit card prototypes that can communicate directly with each other by reflecting Bluetooth signals coming from a smartphone. This opens up possibilities for smart credit cards that can communicate directly with other cards and enable applications where users can split the bill by just tapping their credit cards together.

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