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Georgia Tech Researchers Create an RFID-Sensor Medical Patch

The patch's active UHF tag contains a thin-film battery as well as circuitry printed on an organic substrate, so that it can be worn as a small bandage or sewn into a hospital gown.
By Beth Bacheldor
Apr 08, 2009A group of scientists at the Georgia Institute of Technology has created a thin medical patch containing an ultrahigh-frequency (UHF) active RFID tag and a sensor designed primarily to monitor the health and whereabouts of its patients. The researchers, working at the Georgia Electronic Design Center (GEDC), launched the project in 2007, and are now talking with health-care organizations and medical device companies to create commercial applications for the patch.

The patch is known as the Prototype of the Integrated RFID-enabled Agile Sensor Lab (PIREAS)—and the Greek city of Pireas also happens to be the hometown of Emmanouil Tentzeris, a professor and leader of the GEDC's RFID activities. The tag's antenna, circuit traces and connecting pads are printed on an organic substrate using silver inkjet technology. The tag's other parts—the IC, temperature sensor, battery and oscillator—are connected to the substrate using silver epoxy.

The Georgia Tech medical RFID patch contains a thin-film battery, as well as a printed RFID tag antenna, circuit traces and connecting pads for other components.
Because the tag is so thin and flexible, it can be affixed to a patient with an adhesive backing, or sewn into a hospital gown. The researchers did not employ plastic-type substrates because plastic would not be comfortable enough for wearable electronics; instead, they used organic fiber. "This is one thing that makes our research different," says Li Yang, a GEDC graduate research assistant working on the project. "We've made this on an organic substrate, which is basically a fabric-based substrate, and we've used conductive ink. That means this tag can be made into clothing, it can be bent, it could be a small Band-Aid. It is very low-profile." The substrate, Yang adds, has a hydrophobic (water-repelling) layer coating the surface. "Otherwise," he says, "fiber will absorb a lot of conductive ink and increase the material cost."

The most recent version of the patch has only a temperature sensor, and would need to be affixed as an adhesive bandage. But the group is considering other sensors as well, including one that works with electrocardiograph (ECG) sensors that measure the heart's electrical pulses. The active RFID patch could be sewn into a gown and connected to the ECG sensors on the patient's skin with leads, then wirelessly transmit data from the ECG sensors.

The active RFID tag utilizes a proprietary communications protocol to transmit a 904 MHz signal encoded with its unique ID number and temperature data. The signal can be received and forwarded by other patches, hopping from one to the next, until it is received by an RFID reader.

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