Researchers at Eindhoven University of Technology have developed the world's tiniest temperature sensor that is unencumbered by wires or batteries. Instead, the sensor is powered by radio waves that are part of its wireless network itself.

The sensor has an antenna capable of capturing energy from the router. Once it has enough energy, the sensor switches on, measures the temperature and sends a signal to the router.

The sensor's router has an antenna that sends radio waves to power the device. The router as well as sensors consume very little electricity. The wireless chip can operate even beneath a layer of paint, plaster or concrete, and so can be incorporated into buildings to monitor their temperature.

The wireless temperature sensor measures just 2sq mm and weighs 1.6mg, which is equivalent to a grain of sand. It can currently measure temperature in a 2.5cm range. Researchers expect to widen its coverage range to a meter within a year and finally to 5m.

This kind of technology could also be used to build sensors that measure movement, light and humidity. Peter Baltus, professor of wireless technology at Eindhoven University of Technology and lead researcher, says the applications of the wireless sensor are enormous, ranging from payment systems and wireless identification to smart buildings and industrial production systems. Besides, it would work out to be economical as well.

"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," according to the University's release.