Researchers at Eindhoven University of Technology (TU/e) have developed a tiny, wireless temperature sensor which is powered by the radio waves that are part of the device's own network.  All it needs is energy from a nearby router -- once there's enough, it powers up and starts working. This means that the sensor needs not even a single wire, nor a battery that would have to be replaced. The arrival of such sensors is an important development on route towards smart buildings, for instance. But the applications are many and various.

According to Nanowerk, the smart buildings of the future will be full of sensors that will respond to the residents' every need, and will be as sustainable as possible. Like heating and lighting that only switches on when someone is in the room. That's only possible if these sensors are wireless and need no batteries, otherwise in a large building you would have to change the batteries every day. This is demonstrated by TU/e researcher Hao Gao who will be awarded his PhD on Monday 7 December for his thesis in which he developed a sensor that measures just 2 square millimeters and weights a mere 1.6 milligrams, equivalent to a grain of sand.

Engadget says that, right now, the sensor can't be further than an inch from its host, which isn't exactly practical. Thankfully, this isn't the end of the story. The team hopes to extend that range to nearly 10 feet within a year, and ultimately to 16 feet. If the network-based power takes off, you could see smart homes full of virtually invisible sensors that control all your devices. You could have lights that turn on the moment you enter any room (not just those you care about the most), or heating that shuts off as each room warms up.

Business Standard reports that, since this energy transfer is accurately targeted at the sensor, the router consumes very little electricity. The sensors themselves are made such that their energy consumption is extremely low. The sensor also operates beneath a layer of paint, plaster or concrete. This makes the sensor easy to incorporate in buildings, for instance by 'painting' it onto the wall with the latex, Peter Baltus, TU/e professor of wireless technology, said. 

The same technology enables other wireless sensors to be made, for example to measure movement, light and humidity. The application areas are enormous ranging from payment systems and wireless identification to smart buildings and industrial production systems. The best part may be that these sensors would be very cheap, at about 20 cents each. At that price, it wouldn't cost a fortune to make the upgrade.