Diapers with RFID: Widely Useful or Trivial Pursuit?

Article By : Bill Schweber

A recent project from MIT – yes, MIT – developed a low-cost, easy-to-use system to signal a caregiver via smartphone when a diaper is wet.

I generally have mixed feelings when I see an application that solves what seems to be a trivial problem, using various advanced technologies. On one side, I think “so many engineers and others worked so hard, and for this?” On the other side, sometimes truly beneficial innovations are those that address a small but persistent, widespread problem by leveraging available technologies. After all, what to one person is a small nuisance may be a constant irritation to another person. Not surprisingly, these products seem to peak around the time of CES (formerly the Consumer Electronics Show) every January, but they are not limited to that time window.

A recent project from MIT – yes, MIT – gave me these misgiving and mixed feelings, but also forced me to, yet again, try to look at things from multiple perspectives. The idea and application are simple enough: by embedding a passive radio frequency identification (RFID) moisture sensor, the MIT team developed a low-cost, easy-to-use system to signal a caregiver via smartphone when a diaper is wet.

The RFID tag is inserted in a layer of a standard diaper’s super absorbent polymer (SAP) during manufacturing. (SAP is a type of hydrogel that is typically used in diapers to soak up moisture, among its many other uses). When the hydrogel is wet, the normally non-conductive SAP material expands and becomes slightly conductive — enough to trigger the RFID tag to send a radio signal to a small RFID reader up to about one meter away (Figure 1). The system doesn’t require batteries, as it uses the well-known backscatter principle of RFID tags for power.

Figure 1 A passive RFID triggered by liquid making the hydrogel super absorbent polymer of a diaper become conductive, a nearby RFID reader can be notified that a diaper is wet and report this to a smartphone. (Image source: MIT News)

This is not the first “wet-diaper” detection and signaling system. There ae wireless and Bluetooth-enabled devices that attach to a diaper’s exterior, some with relatively bulky batteries to power long-range connections to the internet. These sensors are designed to be reusable and must be cleaned before attachment to each new diaper. Obviously, this is a relatively costly and effort-intense solution.

In contrast, the passive RFID approach is estimated to cost just a few cents, and the MIT visited diaper production facilities to understand the fabrication process and ensure that their RFID tag would be compatible with the high-volume production. The RFID tag has two elements: an antenna for backscattering radio frequency signals, and an RFID chip that stores the tag’s information. The sensor itself is shaped like a bow tie with the middle consisting of the RFID chip connecting the bow tie’s two triangles, each made of SAP.

Note that RFID is sometimes viewed as competing with ubiquitous “free” bar codes for non-contact identification and labeling. This application is clearly a case where the transformable nature of SAP and linking it to the passive tag accomplishes what a printed bar code cannot.

On one side, this diaper plus passive RFID system still seems like a solution that is bigger and more complicated than the problem itself. Or perhaps it’s a solution looking for a problem to solve – and the world already has plenty of those. On that proverbial other hand, in a toddle daycare or even an elderly-care facility, this sort of quick-check with a scanner could be a real time saver and encourage prompt changing before rashes or other problems can set in. I suppose if I worked taking care of a room of newborns or toddlers who are not trained, I might have a clearer perspective.

This is, of course, not the first time that a solution to what seems a small, almost non-problem really makes a difference to many people. Think of those oh-so-handy “Post-It” notes developed by 3M (you can read 3M’s brief history of their unusual development and path to acceptance at History Timeline: Post it® Notes). Certainly, we had ways before that to attach notes before to things with paper clips, staples, or tape, but these could tear or deface the surface. In contrast, semi-sticky notes certainly made things easier for many people, while the underlying formulation of the adhesive and technology to coat the paper with it in a high-volume production setting with the exact amount of thickness and stickiness is fairly sophisticated.

If you are interested in the details of this MIT RFID-enabled moisture-detecting diaper, you can check out the paper published in IEEE Sensors Journal, “Low-Cost Diaper Wetness Detection Using Hydrogel-Based RFID Tags.” There’s also a broad, less-technical overview at the MIT site, “Low-cost “smart” diaper can notify caregiver when it’s wet.” One thing is sure: this is the type of innovation that, for better or worse, gets a lot of attention in the non-technical media. After all, everyone can understand the “problem” and the user-side simplicity of the solution, even if the passive RFID principle is beyond their understanding.

Can you think of other simple-looking embodiments of advanced technologies which have actually made things better for a lot of people, and with little hassles or downside? What’s your view on this passive RFID sensor tag solution to a near-universal problem: Trivial? Clever? Dumb? Unneeded? Useful? Going to be a winner? Too much? Definitely needed? Or is it some or all the above?

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