Wearable Oral Sodium Sensor to Monitor Salt Intake and Control Hypertension

For people dealing with hypertension and certain other illnesses, eating excess salt raises blood pressure and increases the probability of heart complications. To help monitor salt consumption, scientists have built a flexible and stretchable wireless sensing system designed to be securely worn in the mouth to calculate the amount of sodium a person takes in.

The sensor, based on an ultrathin, breathable elastomeric membrane, incorporates with a miniaturized flexible electronic system that utilizes Bluetooth technology to wirelessly report the sodium intake to a tablet or smartphone. The scientists plan to further reduce the size of the system—which currently looks like a dental retainer - to the size of a tooth.

"We can unobtrusively and wirelessly measure the amount of sodium that people are taking in over time," explained Woon-Hong Yeo, an assistant professor in the Woodruff School of Mechanical Engineering at the Georgia Institute of Technology. "By monitoring sodium in real-time, the device could one day help people who need to restrict sodium intake learn to change their eating habits and diet."

The description of the device has been published May 7 in the early edition of the journal Proceedings of the National Academy of Sciences. The device has been tried out on three adult research participants who wore the sensor system for up to a week while eating both liquid and solid foods including chicken soup, vegetable juice, and potato chips.

According to the American Heart Association, Americans on average consume over 3,400 mg of sodium each day, far more than the limit of 1,500 mg/day it proposes. The association surveyed a thousand adults and discovered that "one-third couldn't estimate how much sodium they ate, and another 54 percent thought they were eating less than 2,000 milligrams of sodium a day."

The new sodium sensing system could solve that challenge by assisting users to better monitor how much salt they ingest, Yeo said. "Our device could have applications for many different goals involving eating behavior for diet management or therapeutics," he added.

Paramount to the development of the intraoral sensor was the replacement of traditional plastic and metal-based electronics with biocompatible and ultrathin parts linked together using mesh circuitry. Sodium sensors are available in the market, but Yeo and his collaborators designed a flexible micro-membrane variety to be combined with the miniaturized hybrid circuitry.

The entire sensing and electronics package was conformally integrated onto a soft material that users can tolerate. The sensor is comfortable to wear, and data from it can be transmitted to a smartphone or tablet. Eventually, the information could go a doctor or other medical professional for remote monitoring.

Woon-Hong Yeo

Computer modeling was used to achieve the flexible design and enhance the mechanical properties of the device for use in the curved and soft oral cavity. The team then used their model to design the real nanomembrane circuitry and pick components.

The device can track sodium consumption in real-time, and record day-to-day amounts. Using an app, the system could guide users planning meals how much of their daily salt allocation they had already eaten. The device can communicate with a smartphone up to 10 m away.

Going forward, the team aims to further miniaturize the device, and test it on users who have various medical conditions to address: obesity, hypertension, or diabetes.

The scientists would also like to eliminate the small battery, which has to be recharged every day to keep the sensor operational. One possibility would be to power the device inductively, which would swap the battery and intricate circuit with a coil that could acquire power from a transmitter outside the mouth.

The study came about because of a long-term goal of creating an artificial taste system that can sense sweetness, pH, bitterness, and saltiness. That study started at Virginia Commonwealth University, where Yeo was an assistant professor prior to joining Georgia Tech.