"Smart" internet-connected devices could indeed make life easier for us, but the things do typically have to be equipped with battery-powered electronics. That may not necessarily be the case for much longer, however, if the Wi-Fi-based LiveTag system reaches fruition.

Developed by a team at the University of California San Diego, the system incorporates simple low-cost tags that can be adhered to everyday non-electronic objects. Those tags consist of patterns of copper foil that are printed onto a flexible paper-like substrate – they don't have any batteries, microchips or additional electronic components.

Each tag reflects radio signals that are already being emitted by an existing Wi-Fi router, in a unique manner. A Wi-Fi receiver, such as that in a smartphone, picks up those reflected signals. If a user should place a finger over a tag, however, they temporarily disrupt that tag's distinct reflection. Upon detecting that disturbance, the receiver proceeds to instruct a smartphone, computer or other electronic device to perform a certain action.

As an example of how the technology could be applied, the researchers created a functioning "paper-thin" interface that could be attached to a wall, clothing or other surface, and used to remotely-control a music player. Made with multiple tags assigned to different music player functions, it features a play/pause button, next track button and sliding volume bar.

Other potential applications include tags that would monitor how often users drink from a water bottle, or that tracked which objects in a store were most often handled by customers. The system could possibly even be used to monitor the progress of stroke patients.

"When patients return home, they could use this technology to provide data on their motor activity based on how they interact with everyday objects at home – whether they are opening or closing doors in a normal way, or if they are able to pick up bottles of water, for example," says Prof. Xinyu Zhang, senior author of the study. "The amount, intensity and frequency of their activities could be logged and sent to their doctors to evaluate their recovery. And this can all be done in the comfort of their own homes rather than having to keep going back to the clinic for frequent motor activity testing."

Additionally, by altering the material and pattern of the tags' coils, they could instead reflect Bluetooth, cellular or LTE signals. It should be noted that in its present form, however, LiveTag is limited to a communications range of one meter (3.3 ft). The team is working on improving that distance, along with developing a method of producing the tags via regular paper-and-ink printing.

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