Radio waves power world’s tiniest temperature sensor

The sensor uses the wireless signal bounced back by a nearby wireless router to power itself up, but there is a snag – since it relies on radio waves the sensor must be 2.5 metres away. Instead, it picks up radio waves from a special router, converts them into electricity, and uses it to transmit readings. 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. Although the most obvious application for the technology will be in developing sensors for IoT applications, the scientists behind the chip said they anticipated a variety of potential uses for it.

The arrival of such sensors is an important development on route towards smart buildings, for instance.

Like many other forecasters, TU/e sees a future where smart buildings are filled with sensors and other devices that gather information and carry out tasks to automate the business of living while making it more sustainable. The sensor will ensure that the aspects like heating and lightingare optimally used and will only be switched-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. And the sensors themselves are made such that their energy consumption is extremely low.

The energy-efficient sensors could be placed under a layer of paint, plaster or concrete without it affecting their performance.

The radio signals are targeted on the sensor, which means the router requires minimal energy to work. The researchers ultimately hope to bump that up to 5 meters. The router can then deduce the temperature based on that signal. The sensor is also created to be as energy efficient as possible.

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.