MARY LOUISE KELLY, HOST:
Many medical tests require blood drawn with a needle. But as NPR's Joe Palca reports, some engineers in California have turned to another bodily fluid for doing these tests - sweat.
JOE PALCA, BYLINE: There are a lot of reasons to use sweat in medical tests.
MALLIKA BARYIA: One is that it can be accessed very conveniently and non-invasively at different body sites.
PALCA: Mallika Baryia is an engineer at the University of California, Berkeley. She says it used to be that testing sweat meant collecting a sample and sending it to a laboratory. She says new technology has changed that.
BARYIA: We can do all of those measurements of molecules, ions, at the point of secretion.
PALCA: As she and her colleagues report in the journal Science Advances, they've developed a flexible patch they can attach to someone's skin. Baryia says the sweat enters a microscopic well embedded in the patch.
BARYIA: And in that well is where we have our sensors for composition analysis.
PALCA: The analysis is sent electronically to a recording device. The patch can measure the salts in sweat, but Baryia says it can also measure things like glucose, although it's not clear whether sweat glucose is as informative as blood glucose. The Berkeley team is just one of several working on sweat patches. John Rogers is at Northwestern University.
JOHN ROGERS: We do things without electronics.
PALCA: Rogers says the patch he's developing with the sports drink company Gatorade uses chemical sensors to measure the sweat.
ROGERS: For electrolytes, we have a specific chemistry that changes from a light pink to a dark red depending on the salt concentration of the sweat.
PALCA: Rogers says if measuring glucose in sweat doesn't turn out to be all that medically useful, he expects measuring other things will be.
ROGERS: Heavy metals.
PALCA: Things like mercury or cadmium that workers might be exposed to on the job.
ROGERS: You can detect those in sweat, so you can measure lead exposure directly. You know, other kinds of heavy metals, they show up immediately in sweat.
PALCA: And there could be other medically relevant compounds measurable in sweat. Berkeley's Mallika Baryia says the patches could open a new era in medical testing.
BARYIA: What challenge needs to be overcome is really understanding where sweat testing is meaningful.
PALCA: Certainly, those of us who don't like needles are eager for sweat testing to prove useful.
Joe Palca, NPR News.
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