Lockheed Martin subsidiary developing passive hydration sensor

By Jonah Comstock
Ronen-Polsky_sm Researcher Ronen Polsky holds the prototype sensor.

Sandia National Laboratories, a division of Lockheed Martin, has developed a potentially wearable hydration and electrolyte sensor that uses tiny needles to sample a negligible amount of interstitial fluid -- the liquid between cells. The study was published this month in the journal Advanced Healthcare Materials.

“We’re proposing a minimally invasive way to move away from centralized laboratory testing,” Researcher Ronen Polsky said in a statement. "We want to make the device wearable, noninvasive, and with real-time readout to constantly measure things a doctor might normally order for laboratory tests."

By using needles so small they don't traumatize the skin, the prototype device could be the first wrist-worn device to accomplish true continuous, passive, noninvasive monitoring of hydration and electrolytes, measurements that could be very valuable to athletes, soldiers, or just fitness-conscious consumers. The device could even open a pathway to the elusive realm of passive nutrition tracking, as it can be modified to detect specific electrolytes like potassium, sodium or calcium. 

The paper is a proof of concept, but the researchers have not yet tested the device out on humans, or in a wrist-worn form factor. Justin Baca, a physician and researcher at the University of New Mexico, will take the device into human testing next.

“Development of this benchtop device into a handheld model for consumers and patients will be a true partnership between a clinician and an engineer," Baca said in a statement. "We’re trying to get at this problem from the beginning to develop the best needle geometry.”

The eventual consumer product could even be not just a sensor but a therapy device. Researchers envision a device that could use the same needles it uses for sampling to deliver electrolytes that were found to be deficient. According to Polsky, investors have expressed interest in commercial applications for the technology.

Passive hydration tracking has been in the news recently because it was rumored to be a part of Apple's healthcare plans, although MobiHealthNews was skeptical of that prediction, precisely because passive hydration tracking hasn't yet been scientifically validated.

A few other efforts have been made in the past, including Philometron, which worked with DARPA in 2010 on a peel-and-stick sensor for the military. That technology spun out to become Corventis, using the fluid monitoring capability for congested heart failure patients instead. Cambridge, Massachusetts-based MC10 is also developing a peel-and-stick passive hydration sensor.