Smartphones, smart TVs, and now... smart diapers?

Researchers at the University of Tokyo make a super-thin sensor that can go inside diapers to alert caretakers when it's time for a change.

Michael Franco
Freelancer Michael Franco writes about the serious and silly sides of science and technology for CNET and other pixel and paper pubs. He's kept his fingers on the keyboard while owning a B&B in Amish country, managing an eco-resort in the Caribbean, sweating in Singapore, and rehydrating (with beer, of course) in Prague. E-mail Michael.
Michael Franco
3 min read
Diaper sensor
The new sensor is thin enough to be comfortable, but robust enough to transmit valuable data. The University of Tokyo

Imagine this: You're sitting in your living room watching the season premiere of "Game of Thrones" when suddenly you get a text message from your 2-month-old daughter saying her diaper needs to be changed. No, she's not a super-smart infant who learned how to text at birth -- but her diaper is pretty smart and it knows when it's wet and needs your help -- even if winter is finally coming right this second.

That future that might be possible, thanks to a new invention from Takao Someya and a team of researchers at the University of Tokyo. This team, in July 2013, announced in the journal Nature that they'd come up with flexible circuits, thinner than a piece of plastic wrap, that could be implanted in the body to monitor body temperature or blood pressure or implanted on the roof of the mouth to be used as a touch pad for quadriplegics.

Now, they've applied their research to a truly worthwhile problem -- knowing when a diaper is soiled without having to undress the wearer first.

While another recent attempt to make diapers more intelligent involved QR codes, the Tokyo team, led by Someya and Takayasu Sakurai (both professors at the university) have created a disposable, organic sensor that can be embedded in a diaper. The sensor, which is printed on a film using inkjet technology, responds to conditions that cause a change in electrical resistance, such as pressure, temperature, and -- most relevantly -- wetness. When it senses that a diaper needs to be changed, it sends a signal to an external data-reading device.

Someya believes he can produce each sensor for mere pennies, so that it wouldn't add much cost to diapers. He also told me via e-mail (after I expressed some safety concerns), that the device is completely safe to wear next to the skin, primarily because it receives its power from the external monitoring device, rather than generating its own electricity (which could lead to a shocking experience). He added that its bendability was a plus. "It is completely flexible," he said, "therefore it's much safer than the conventional rigid electronics when it is put very close to skin."

The device needs to be within a few inches of the film to work, so the diaper wearer would have to be prepared to have his or her private parts scanned. Not such a big deal perhaps for infants, but one application of the technology would be to install it in adult diapers where the sensor would eliminate the sometimes difficult chore of undressing patients to see if they need changing. And we're not so sure how Grandpa would feel about having a gizmo waved around his nether regions.

Someya, who's presenting his research at the 2014 IEEE International Solid-State Circuits Conference (ISSCC) in San Francisco on Wednesday, says his team is investigating ways to boost the distance of the signal so that up-close monitoring won't be necessary. Which means that maybe, someday, you'll be able to get that text from your daughter -- hopefully before your favorite show starts.

Update, Thursday at 4:25 p.m. PDT: Added comments from Someya on the safety of the device.