The Auto-ID Lab at MIT has long been at the forefront of developing RFID technology. Now engineers in this group are flipping the technology toward a new function: sensing. They have developed a new ultra-high-frequency, or UHF, RFID tag-sensor configuration that senses spikes in glucose and wirelessly transmits this information. In the future, the team plans to tailor the tag to sense chemicals and gases in the environment, such as carbon monoxide.
Imagine creating thousands of these inexpensive RFID tag sensors which you can just slap onto the walls of an infrastructure or the surrounding objects to detect common gases like carbon monoxide or ammonia, without needing an additional battery.
Currently, RFID tags are available in a number of configurations, including battery-assisted and “passive” varieties. Both types of tags contain a small antenna which communicates with a remote reader by back scattering the RF signal, sending it a simple code or set of data that is stored in the tag’s small integrated chip.
Battery-assisted tags include a small battery that powers this chip. Passive RFID tags are designed to harvest energy from the reader itself, which naturally emits just enough radio waves within FCC limits to power the tag’s memory chip and receive a reflected signal.
The researchers built a simple circuit around the memory chip, enabling the chip to switch to a local energy-assisted mode only when it senses a certain stimuli. When in this assisted mode (commercially called battery-assisted passive mode, or BAP), the chip emits a new protocol code, distinct from the normal code it transmits when in a passive mode. A reader can then interpret this new code as a signal that a stimuli of interest has been detected.
The design is also more efficient. A tag can run passively on RF energy reflected from a nearby reader until a stimuli of interest comes around. The stimulus itself produces a charge, which powers a tag’s chip to send an alarm code to the reader. The very act of sensing, therefore, produces additional power to power the integrated chip.
The researchers developed an RFID glucose sensor. They set up commercially available glucose-sensing electrodes, filled with the electrolyte glucose oxidase. When the electrolyte interacts with glucose, the electrode produces an electric charge, acting as a local energy source, or battery.
In this design just plug and play with these commercially available electrodes, which makes this whole idea scalable. Then you can deploy hundreds or thousands, in your house or in a facility where you could monitor boilers, gas containers, or pipes.
News Source: http://news.mit.edu/2018/mit-engineers-configure-rfid-tags-to-work-as-sensors-0613
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