One step closer to batteryless smart devices

By David Jones

We are now one step closer to batteryless smart devices, say scientists at the University of Waterloo in Canada. They say they have taken a massive step towards making smart devices that do not need batteries. In other words, battery-free smart devices. Therefore, they do not need recharging either.

These Internet of Things (IoT) devices feature an IP address for connectivity. Batteryless IoT devices are ideal for placement in areas that are off the grid. Also, their maintenance costs are significantly lower.

Some of these IoT devices have sensors that detect their environment. They can, for example, measure a room’s ambient temperature or determine what levels of light or motion there are.

Making sustainable and batteryless devices

One of the biggest challenges with these devices is making them sustainable and batteryless.

Professor Omid Abari, Professor Srinivasan Keshav, and Dr. Ju Wang have found a way to hack RFID (radio frequency identification) tags. RFID tags are electronic tags, consisting of a chip and an antenna, that exchange data with RFID readers through radio waves. They are the ubiquitous thin strands of metal with a small chip that exist in many objects. They make it possible for devices to sense the environment.

Abari is an Assistant Professor at Waterloo’s Cheriton School of Computer Science. He is also Director of Waterloo’s ICON Lab. Keshav is a Professor at the Cheriton School of Computer Science. Wang is a Postdoctoral Fellow at the Cheriton School of Computer Science.

The researchers wrote an article about their study and findings. It appeared in the Proceedings of the 24th Annual International Conference on Mobile Computing and Networking (citation below).

Regarding hacking the RFID tag, Dr. Wang said:

“It’s really easy to do. First, you remove the plastic cover from the RFID tag, then cut out a small section of the tag’s antenna with scissors, then attach a sensor across the cut bits of the antenna to complete the circuit.”

RFID tags, in their stock form, provide just location and identification. The researchers have cut the tag’s antenna and placed a sensing device across it. It’s the hack that gives the RFID tag the ability to sense its environment.

Batteryless smart devices - altering the RFID tag
The researchers modified the RFID tag by cutting out a small part of its antenna (silver ribbon). They then placed a small light-sensing phototransistor or temperature-responsive resistor on it. (Image: eurekalert.org. Credit: University of Waterloo)

Giving the tag eyes

So that the tag can see, the researchers hacked an RFID tag with a phototransistor. The phototransistor is a tiny sensor that responds to light intensity.

When they exposed the phototransistor to light, it changed the characteristics of the RFID’s antenna. This, in turn, caused the signal going to the reader to change.

The researchers then developed an algorithm on the reader side. The algorithm monitors change in the tag’s signal, which is how it senses different levels of light.

One of the simplest hacks is to add a switch to an RFID tag so that it acts as a keypad. The keypad responds to touch.

Prof. Abari said:

“We see this as a good example of a complete software-hardware system for IoT devices. We hacked simple hardware – we cut RFID tags and placed a sensor on them. Then we designed new algorithms and combined the software and hardware to enable new applications and capabilities.”

“Our main contribution is showing how simple it is to hack an RFID tag to create an IoT device. It’s so easy a novice could do it.”

Citation

“Challenge: RFID Hacking for Fun and Profit,” Srinivasan Keshav, Ju Wang, and Omid Abari. Proceedings of the 24th Annual International Conference on Mobile Computing and Networking, October 29-November 2, 2018, New Delhi, India, 461- 70. DOI: 10.1145/3241539.3241561.