'Smart' diaper tells caregiver when it's wet

MIT researchers develop smart diaper
New disposable, affordable “smart” diaper embedded with an RFID tag is designed by MIT researchers to sense and communicate wetness to a nearby RFID reader, which in turn can wirelessly notify a caregiver that it’s time for a change. (MIT)

A wet diaper is a signal for the caregiver to give an infant immediate attention. A wet diaper worn too long can cause painful rashes and discomfort for both baby and parents.

To combat this issue, MIT researchers have developed a "smart" diaper embedded with a moisture sensor that can alert a caregiver when a diaper is wet. When the sensor detects dampness in the diaper, it sends a signal to a nearby receiver, which in turn can send a notification to a smartphone or computer.

The sensor comprises a passive radio frequency identification (RFID) tag, placed below a layer of super absorbent polymer, a type of hydrogel that is typically used in diapers to soak up moisture. When the hydrogel is wet, the material expands and becomes slightly conductive -- enough to trigger the RFID tag to send a radio signal to an RFID reader up to 1 meter away.

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According to the researchers, the design is the first demonstration of hydrogel as a functional antenna element for moisture sensing in diapers using RFID. They estimate that the sensor costs less than 2 cents to manufacture, making it a low-cost, disposable alternative to other smart diaper technology.

Companies looking into smart diaper technology are considering wetness sensors that are wireless or Bluetooth-enabled, with devices that attach to a diaper's exterior, along with bulky batteries to power long-range connections to the internet. These sensors are designed to be reusable, requiring a caregiver to remove and clean the sensor before attaching it to each new diaper. Current sensors being explored for smart diapers retail for over $40, according to the researchers.

The diapers MIT is researching use RFID tags, which typically comprise an antenna to backscatter radiofrequency signals, and an RFID chip that stores the tag’s information. The RFID tags work not just as wireless trackers, but also as sensors. Most recently, as part of MIT’s Industrial Liaison Program, the research team started collaborating with Softys, a diaper manufacturer based in South America, to see how RFID tags could be configured as low-cost, disposable wetness detectors in diapers. 

The scientists believe smart diapers could potentially help record and identify certain health problems, such as signs of constipation or incontinence. The sensor may be especially useful for nurses working in neonatal units and caring for multiple babies at a time.

Pankhuri Sen, a research assistant in MIT's AutoID Laboratory, envisions that the sensor could also be integrated into adult diapers, for patients who might be unaware or too embarrassed to report themselves that a change is needed.

"Diapers are used not just for babies, but for aging populations, or patients who are bedridden and unable to take care of themselves," Sen said. "It would be convenient in these cases for a caregiver to be notified that a patient, particularly in a multibed hospital, needs changing."

"This could prevent rashes and some infections like urinary tract infections, in both aging and infant populations," added collaborator Sai Nithin R. Kantareddy, a graduate student in MIT's Department of Mechanical Engineering.

Kantareddy, and their colleagues at MIT, including Rahul Bhattacharryya and Sanjay Sarma, along with Joshua Siegel at Michigan State University, published their results in the journal IEEE Sensors.

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