Eindhoven student Hao Gao was due to receive a Ph.D. earlier this month for his thesis in which he discusses his development of the sensor that has an area of 2 square millimeters and weighs 1.6 mg. The sensor is made using a 65 nm CMOS manufacturing process.
A specially developed wireless router communicates with the sensor, which has an antenna on chip and picks up both energy and information from the millimeter wave signals. The current version of the sensor has a range of 2.5 cm but researchers hope to extend this to a metre within a year.
Temperature sensor on the finger of PhD-student Hao Gao. Photo: Bart van Overbeeke. Source: Technical University of Eindhoven.
The autonomous nature of the temperature sensor means it can be put behind plasterboard or included in a screed of concrete or paint
The sensor stores the energy received and once there is enough, switches on, measures the temperature and sends a signal to the router. Each temperature is indicated by a slightly different frequency at which the return signal can be sent. The router determines the temperature by the distinctive frequency.
Next: Broader application