If you’re one of the approximately 36 million adults in the United States with high blood pressure (also called hypertension), your doctor may have lectured you about the importance of reducing your sodium intake. Maybe you listened, and maybe you even intended to follow your doctor’s advice.
But sodium, the primary component of table salt, is everywhere in our modern diets—in snack foods, in restaurant meals, even in beverages—and your good intentions probably didn’t get you very far.
To tackle this problem, researchers at the Georgia Institute of Technology have invented a flexible electronic sensor that can be embedded in a dental retainer for real-time monitoring of sodium intake. The device, which they described in the journal PNAS, could send info to your phone, giving you instant data about whether you’re busting your low-sodium diet.
Whether you decide to change your diet based on that data is another question entirely. But getting the data is the first step.
W. Hong Yeo, an assistant professor of micro and nano engineering who led the research team, says it would also be possible to stick the sensor directly to the tongue or the roof of the mouth, or to laminate it onto a tooth. The soft retainer they used in this experiment was just phase one. “For the first prototype device, we wanted to offer easy handling and cleaning capability via the integration with a soft retainer,” he said.
Yeo says the biggest challenge was making the entire electronic device soft, flexible, and comfortable enough to wear in the mouth. So the team designed a chip that uses stretchable circuits mounted on an ultrathin porous membrane.
A new wireless sensor made of stretchable circuits mounted to a porous membrane can measure how much sodium a person eats in real time.Image: Georgia Institute of Technology
Its power source is a rechargeable micro-coin battery (measuring 6.8 mm in diameter), which could continuously monitor real-time sodium intake for 12 hours. Yeo thinks that’s a long enough battery life for practical use, as a wearer could put in the retainer just at meal times and recharge it at night. But his team is considering removing the battery in the design of an even smaller sensor, which could receive power from an external source via inductive coupling.
The sodium sensor itself uses inexpensive materials that respond to the presence of sodium ions. To test the gadget, Yeo’s team first had people take sips of water with various concentrations of salt. When it proved adept at measuring those sodium levels, they moved to a harder challenge: real food and drink. The test subjects took a gulp of veggie juice, slurped up a mouthful of chicken noodle soup, and crunched down on a potato chip.
The device did well with the juice and soup, but the chip was a little trickier. The measurement of its sodium level showed an initial spike, caused by the chip physically hitting the sensor, and the reading was significantly off from the actual sodium value, a discrepancy Yeo chalks up to dilution from saliva.
But both these issues can be addressed by good data processing, he says. If the software system is calibrated with the user’s baseline sodium levels, it could remove spikes and outlier readings. And it could be connected to an existing health or fitness app (such as MyFitnessPal) that contains info about the sodium content of millions of different food items—including potato chips.
The team has already created an Android app, and the sensor uses Bluetooth to send its data to a smartphone or tablet. While Yeo says his team is working to miniaturize the device further, he thinks it’s nearly ready for practical use. “It’s very close to commercialization, it just depends on companies coming and expressing interest,” he says.
The data is out there. Whether medical device companies decide to act on it—or people choose to make dietary changes based on it—is another question entirely.
Eliza Strickland is a senior editor at IEEE Spectrum, where she covers AI, biomedical engineering, and other topics. She holds a master’s degree in journalism from Columbia University.