Smart devices implanted in the body have thus far not been able to communicate via Wi-Fi due to the power requirements of such communications. Surgery is required when the battery in a brain stimulator or a pacemaker needs to be replaced. Not only is this expensive, but any surgery has inherent risks and could lead to complications. It is therefore critically important that the battery life in implanted medical devices be preserved for as long as possible.

Other constraints limiting how much power a device can use include their location in the body and their size. New emerging devices that could one day reanimate limbs, stimulate organs, or brain implants that treat Parkinson’s disease are limited by the same factors.

Implants and Smartphone

Smartwatches, smartphones and other similar Bluetooth enable devices continuously transmit communication signals. A team from the University of Washington (UW) consisting of computer scientists and electrical engineers, have developed a method that utilizes these signals and converts it to Wi-Fi signals. The new method uses ten thousand times less energy than traditional methods do. Another huge advantage of this method is that it does not need any specialized equipment.

“Interscatter” communication creates low-power Wi-Fi transmissions with the help of smartphones. In this example, Bluetooth signals from a smartwatch (left) was used to transmit data from a neural device, that can be implanted in human brain (right), to a smartphone via Wi-FI. Image credit: Mark Stone/University of Washington

The process developed by the team uses a communication technique called backscatter. Devices can exchange information by using existing signals and simply reflecting them. The team has dubbed the technique used in their development “interscattering” because it allows inter-technology communication by creating Wi-Fi transmissions by using Bluetooth signals.

Co-author Joshua Smith, associate professor of electrical engineering and of computer science and engineering at UW, explains that Wi-Fi, ZigBee or Bluetooth radios embedded in everyday mobile devices such as headsets, smartphones, laptops, tablets and watches can be used to generate interscatter communication. The devices act as both the receivers and sources for the reflected signals.

In a first of its kind demonstration, the team showed that power-limited devices could talk to others by using standard Wi-Fi. Co-author Vamsi Talla, a recent UW doctoral graduate in electrical engineering, notes that the breakthrough came about because of their device not having to generate its own Wi-Fi signals. Talla, who is now a research associate in the Department of Computer Science & Engineering, goes on to say their technology creates Wi-Fi by using Bluetooth transmissions from any mobile devices that are close enough. That means that the limitation of implanted devices not being able to send data to smartphones and other mobile devices using Wi-Fi is something of the past.

smart contact lenses
UW engineers the first smart contact lens antenna that can communicate with everday devices like smartphones or smartwatches. Image credit: Mark Stone/University of Washington

In one of the demonstrations done by the team, a smart contact lens outfitted with an antenna receives a Bluetooth signal from a smartwatch.  The UW team established a state-of-the-art method to transform the Bluetooth transmission into a “single tone” signal so that a blank slate is created on which new information can be written. Once written, the data can be further transformed and manipulated. The contact lens can encode data by backscattering the single tone signal. Collected information such as health data is then compiled into a standard Wi-Fi packet that can ultimately be read by a laptop, smartphone or tablet.

Lead faculty Shyam Gollakota, assistant professor of computer science and engineering, explains that Bluetooth devices use scrambling to randomize data transmissions. The team reverse engineered this scrambling process enabling Bluetooth-enabled devices to send out a single tone signal. A software app on the device is used to control and manage the process. The development was however not without challenges. The backscattering process creates a mirror image copy of the signal. This unwanted copy consumes bandwidth needlessly and interferes with networks on the mirror copy Wi-Fi channel. The development of a single sideband backscatter technique does however eliminate this accidental byproduct.

Co-author and electrical engineering doctoral student Bryce Kellogg points out that the result of this technique is that other Wi-Fi networks operate without interference while their technology utilizes as much bandwidth as a Wi-Fi network does.

Working from the UW’s Networks and Mobile Systems Lab and Sensor Systems Lab, the engineers set about to conquer previously infeasible applications. Their three proof-of-concept (POC) models included an implantable neural recording device and a smart contact lens. These devices are able to communicate directly with watches and smartphones while consuming only tens of microwatts of power.

interscatter communication-example
Interscatter communication examples include:
1. A smart contact lens that uses Bluetooth signals from a smartwatch and sends its data to a smartphone.
2. Bluetooth headset and smartphone that communicates with an implantable brain interface
3.) Credit cards communicating by backscattering Bluetooth connections from a smartphone. (Image credit: University of Washington)


Other than being used with implanted devices, this technology has a whole host of other potential applications. One of these for which prototypes have already been built is smart credit cards. The cards reflect Bluetooth signals coming from a smartphone and then communicate directly with each other. This makes it possible for the smart credit cards to communicate directly with other cards and enable applications. Possible application for this include the scenario where users can split the bill by just tapping their credit cards together.