Smart Threads Monitor Pregnancy Complications and Infant Health

A prototype belly band sensor around a mannequin simulating a pregnant woman. (Image courtesy of Science Nation.)

An engineer, a doctor, and a fashion designer walk into a bar. There’s no punchline, because the three professionals are simply there to discuss their collaborative research into “belly bands”, a smart fabric with RFID technology for women with high-risk pregnancies.

The belly band is exactly what it sounds like: a comfortable, stretchable fabric that pregnant women wear around their abdomen. It serves as a sensor that can monitor contractions, respiration patterns and limb movements, tracking data and alerting the doctor’s office if necessary.

Knitting Antennas that Change Shape

The belly band sensor is composed of a folded dipole antenna equipped with an inductively coupled, passive RFID tag. An in-home RFID reader, similar to a baby monitor, is used to track and send data from the band.

The sensor works using the returned signal strength indication (RSSI) of the RFID backscatter to detect deformation of the fabric. When the shape of the antenna changes, such as by the woman breathing, its resonant frequency shifts. This causes a variation in RSSI seen at the reader, providing a way to track changes in the woman’s body using machine learning techniques.

Block diagram of the full system. The RFID reader interrogates the wearable sensor, which responds with RSSI values that vary based on the level of stretching. The RSSI data are transferred to the computer for the machine learning processing and final display of the breathing activity. (Image and caption courtesy of IEEE Transactions on Biomedical Circuits and Systems.)

“We’re looking at making antennas out of knitted conductive materials,” said electrical and computer engineer Kapil Dandekar. “As those antennas stretch due to, say, uterine contraction in a pregnant woman or infant respiration, we can detect changes in signal characteristics that come off of that antenna and process that to infer what’s happening biologically.”

The use of passive RFID technology means that there’s no need for a battery in the sensor, but this is just one step in making the belly band suitable for everyday use. That’s why industrial and fashion designer Genevieve Dion is searching for ways to make the sensor both comfortable and practical.

“If it doesn’t fit well, you’ll be tugging on it, and you won’t want to wear it, and then it’s useless,” said Dion. “But also if it doesn’t interact well, then it’s a gadget, because you have to fuss with it. So I think it has to be well-designed so that we can be comfortable in them, but it also has to be well-engineered in many ways so that it functions properly.”

The team is also developing a smaller version of the belly band to monitor infants at risk for sleep apnea. Using a medical programmable mannequin, the team’s experiments have demonstrated early success in differentiating breathing and non-breathing patterns from the RSSI data.

For more news about smart clothing, check out Smart Thread Collects Data from Sutures and Wearables. Or, to learn more about how connected technology is monitoring infant health, read Clever IoT Engineering Helps Infants and Parents Alike.