New wireless sensor never needs charging

Dutch researchers built a wireless sensor that can draw power from a nearby wireless network. The sensor weighs as much as a grain of sand, and could be "painted" into walls to monitor temperature, light, movement, or humidity.

Bart van Overbeeke/Eindhoven University of Technology
Ph.D. student Hao Gao holds the tiny wireless sensor on his fingertip. The sensor doesn't need batteries or wires, since it can draw power from a wireless network.

The Internet of Things is expanding quickly ­– researchers at Intel predict that it will comprise 40 to 50 billion connected garments, watches, thermostats, appliances, and more by the end of the decade – but it’s also having some growing pains.

One of those pains is security. Researchers are discovering that many Internet-connected devices, including baby monitors and home security cameras, are vulnerable to common hacking attacks. Another is power. If we're heading toward a future in which most devices we interact with are connected to one another and to the Internet, such a reality shouldn’t include tangles of wires and power strips protruding from every surface.

A team of researchers at Eindhoven University of Technology in the Netherlands may have a solution to the power issue. They built a wireless temperature sensor that can charge itself using the electromagnetic waves in the air around it. In other words, by connecting to the Internet wirelessly, the sensor is automatically charging itself through those wireless waves.

Right now, the implementation is simple. The sensor, which is about 0.08 inches on a side and weighs the same as a grain of sand, will power itself on once it’s placed near a special wireless router. The router’s directional antennae send radio waves to the sensor so it can stay powered indefinitely.

Unfortunately, it won’t work if there’s more than two and a half centimeters (about an inch) of distance between the sensor and the router, which makes it hard to use the sensor for any real-world applications. However, the researchers said in a press release that they expect to extend that range to a yard within a year and that the technology will eventually work up to 16 feet away from a router.

One of the researchers, professor Peter Baltus, noted that the sensor can work even beneath a layer of paint, plaster, or concrete. That means future buildings could have tiny temperature, light, or humidity sensors embedded in the walls, allowing the building to automatically adjust its own environmental controls according to the occupants’ preferences. And if the underlying technology that allows a sensor to pull power from a wireless network takes off, current battery-powered devices could be replaced by tiny embedded sensors that control lights, heating and cooling, wireless payment, and more.

The Eindhoven researchers say the sensors could be made at scale for about 20 cents each, and that because each sensor operates on a “slightly distinctive” frequency, a number of these sensors, measuring everything from light to movement to humidity, can be powered by a single wireless router.

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