For some infants, a wet diaper is cause for an instant, vociferous demand to be changed, while other babies may be unfazed and happy to haul around the damp cargo for lengthy periods without complaint. But if worn too long, a wet diaper can cause painful rashes, and miserable babies -- and parents.
Now 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 consists of a passive radio frequency identification (RFID) tag, that is 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.
The researchers say 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.
Over time, smart diapers may help record and identify certain health problems, such as signs of constipation or incontinence. The new 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. It would be convenient in these cases for a caregiver to be notified that a patient, particularly in a multibed hospital, needs changing." Pankhuri Sen, research assistant in MIT's AutoID Laboratory
"This could prevent rashes and some infections like urinary tract infections, in both aging and infant populations," adds collaborator Sai Nithin R. Kantareddy, a graduate student in MIT's Department of Mechanical Engineering.
Sen, Kantareddy, and their colleagues at MIT, including Rahul Bhattacharryya and Sanjay Sarma, along with Joshua Siegel at Michigan State University, have published their results today in the journal IEEE Sensors. Sarma is MIT's vice president for open learning and the Fred Fort Flowers and Daniel Fort Flowers Professor of Mechanical Engineering. Sticker sense
Many off-the-shelf diapers incorporate wetness indicators in the form of strips, printed along the outside of a diaper, that change color when wet -- a design that usually requires removing multiple layers of clothing to be able to see the actual diaper.
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, Sen estimates, retail for over $40.
RFID tags in contrast are low-cost and disposable, and can be printed in rolls of individual stickers, similar to barcode tags. MIT's AutoID Laboratory, founded by Sarma, has been at the forefront of RFID tag development, with the goal of using them to connect our physical world with the internet. Related Stories
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