The tags harvest some of the RF energy sent by the reader to power up an integrated chip that stores data, and uses the remaining energy to modulate the returning signal. But in a traditional RFID system that amounts to only a few microwatts of power, which limits their communication range to less than a meter.
The researchers' sensor consists of an RFID tag – containing an IC that is directly connected to an array of customized perovskite solar cells - built on a plastic substrate. As with traditional RFID systems, a reader sweeps the room, and each tag responds. But instead of using energy from the reader, say the researchers, it draws harvested energy from the perovskite cell to power up its circuit and send data by backscattering RF signals.
The initial RFID circuit was prototyped to only monitor temperature, but, say the researchers, their aim is to scale up and add more environmental-monitoring sensors to the mix, such as humidity, pressure, vibration, and pollution. Deployed at scale, the sensors could especially aid in long-term data-collection indoors to help build, say, algorithms that help make smart buildings more energy efficient.