MIT's 2-cent RFID tags sense soiled diapers on the cheap
The icky business of soiled diapers has motivated many to pursue connected nappies that alert carers when they’re in need of changing, but scientists at MIT are now putting forward a more cost effective option. The team’s new smart diapers make use of an RFID tag that works with a hydrogel to form a cheap moisture sensor, which sends an alert to a carer when it’s time for a change.
While there have been a number of attempts at developing smart diapers that can help avoid rashes and discomfort in babies carrying around their own waste, the MIT team sees room for improvement in a number of ways. Some, like the TweetPee concept from Huggies way back in 2013, require clip-on hardware, and others call for bulky batteries to power the wireless communications.
Moreover, current solutions are rather costly, according to Pankhuri Sen, a research assistant in MIT’s AutoID Laboratory, who estimates that the sensors needed for these types of devices can retail for more than US$40. Her and her colleagues set out to build a far cheaper option, which caregivers can therefore easily dispose of once sullied.
The sensor is made of an RFID tag that can be printed out as an individual sticker, which is then placed below a layer of hydrogel super absorbent polymer (SAP). As the hydrogel moistens, it expands and, thanks to copper embedded inside, becomes slightly conductive. This enables the RFID tag to send a radio signal to an RFID reader up to 1 meter (3.2 ft) away.
This RFID reader could be placed in the basinet or baby's room, and relay the signal to a parent's smartphone or computer. The team estimates that the sensor costs less than two cents to make, and imagines that it mightn't just prove useful for infants, but adults, too. This could mean identifying health problems like constipation or incontinence, and helping out nurses in busy wards.
“Diapers are used not just for babies, but for aging populations, or patients who are bedridden and unable to take care of themselves,” Sen says. “It would be convenient in these cases for a caregiver to be notified that a patient, particularly in a multibed hospital, needs changing.”
The research was published in the journal IEEE Sensors.