Cut the Cord

Wearable electronic devices can offer plenty of utility, but if they do not get recharged on a regular basis, they are not of any use at all. And if those devices are designed to track the health of the wearer, then there will always be a gap in data collection during the recharging period. These factors limit the effectiveness of wearable electronics, and also frustrate users to the point that they often stop using them altogether.

A team of researchers at the Massachusetts Institute of Technology have created a shocking solution to remedy this current state of affairs — if you do not mind using your body as a wire to transmit power, that is. While the name of their technology, ShaZam, may sound more like something you would hear about in an infomercial than read about in an academic paper, it looks to be a promising advance in intra-body power transfer.

The concept was prototyped with a wrist-worn device. An electrode, which could be placed on a desk, keyboard, steering wheel, or any number of other locations, injects an RF signal into body tissue that comes into contact with it. This serves as the forward electrical signal. Of course we only have one skin surface, so there is no return path to complete the electrical circuit. To establish that return path, another copper electrode is positioned nearby, but not in direct contact with the body. Natural capacitance between the RF signal in the body and this nearby electrode serves as the return path for the electrical current.

The feasibility of the technology was assessed in a study through ten participants that interacted with a keyboard on a desk, a laptop, and the steering wheel of a car — all of which were instrumented with electrodes as previously described. These scenarios showed that in principle the idea can work to transfer power through the human body in real world situations. The desk-based scenario was found to transfer the greatest amount of power due to the layout of the various electrodes, which shows the importance of proper electrode placement.

While the amount of power being transferred is very small and causes no pain, many people may not find the concept to be very agreeable. However, when study participants were informed about the safety of the device, they reported that they were not concerned about their safety.

Before you try to build your own ShaZam implementation to charge your smartwatch, note that the system has only been tested to transfer 0.5 - 1.0 milliwatts of power thus far. This limits the applications of ShaZam to specialized, low-power devices at present. The team also noted variability in the amount of power that could be transferred depending on the season, and the individual user. They are presently working to minimize such variabilities.