RFID Tags Used to Covertly Collect Vital Signs

Researchers at Cornell University (Cornell; Ithaca, NY, USA) have developed small RFID tags that emit radio waves that bounce off the body and internal organs, and are then detected by an electronic reader that gathers the mechanical motion data from a location elsewhere in the room, using near-field coherent sensing (NCS). The RFID tags are powered by electromagnetic energy supplied by the central reader; since each tag has a unique ID code, up to 200 people can be monitored simultaneously using just one central reader.

According to the researchers, the approach has two possible implementations, using either passive or active RFID tags. Passive tags can be integrated into garments at the chest and wrist areas, with the two multiplexed far-field backscattering waveforms collected at the central reader to retrieve the heart rate, blood pressure, respiration rate and breathing effort of a single person. The researchers suggest that the passive approach can be used when minimal deployment and maintenance costs are required.

To maximize reading range and immunity to multipath interference caused by indoor occupant motion, active RFID tags could be placed in the front pocket and in the wrist cuff of the patients clothing in order to measure the antenna reflection due to NCS, with vital signals sampled and then transmitted entirely in digital format. As a result, the active system can monitor multiple people simultaneously, and could lead to the cost-effective automation of vital sign monitoring in care facilities. The study was published on November 27, 2017, in Nature Electronics.

“The system works like radar. If this is an emergency room, everybody that comes in can wear these tags or can simply put tags in their front pockets, and everybody's vital signs can be monitored at the same time. I'll know exactly which person each of the vital signs belongs to,” said study co-author professor of electrical and computer engineering Edwin Kan, PhD. “The technology could also be used to measure bowel movement, eye movement, and many other internal mechanical motions produced by the body.”

In NCS, more electromagnetic energy is directed into the body tissue than with typical radiofrequency methods, where the energy is mostly reflected by the body surface, resulting in the backscattered signal from internal organs implicitly amplified by the multiplexed radio signals. At the same time, the shorter wavelength inside the body renders a small mechanical motion into a relatively large phase variation, which also increases sensitivity.

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