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Hank: You’ve probably seen them all over your social media feeds, and maybe even posted some yourself: Exercise statistics. Look at the thing I did. I’m proud! With all kinds of wearables turning exercise into a more and more exact science, your friends can announce that they hit 10,000 steps at 2:54 PM today, and you can tell them all about how you burned 683 Calories on your 11.5 kilometer run. And in a few years, you might have another set of stats to add to the list -- a set that’s a little more personal.

Because this week, engineers from the University of California, Berkeley unveiled the first wearable device that can quickly and accurately measure the qualities of sweat in a ton of detail. In other words, it tells you what you’re sweating out... while you’re working out. Sweat coats the surface of your body during heavy exercise, cooling you down as it evaporates. It’s mostly water, but sweat’s also chock full of other molecules -- like glucose and lactic acid -- as well as ions, like sodium and potassium. The concentrations of these things in your sweat can reveal a lot about your workout, and your health overall. And that’s what this new device is designed to detect.

You wear it on your wrist or forehead, where it’ll get a nice, steady supply of sweat as you work out. The sweat flows over an array of sensor modules, each responsible for detecting a particular substance and producing an electrical signal based on how much it finds. So, what could your sweat say about you? Well, for one thing, it could probably give you an extra-early warning that you’re getting dehydrated. If you happen to be the kind of person who enjoys long distance runs, you’ll know first-hand how important it is to stay hydrated and maintain your blood sugar levels during races. This sensor can help with that.

A sudden increase in the sodium ions in your sweat could be a sign of dehydration, and the amount of glucose in your sweat is related to your blood sugar. So, in theory, you could tell a sensor like this to beep at you when it’s time to crack open an energy bar or sports drink. The sensor also tests for lactic acid, a sign your body isn’t getting quite enough oxygen to meet the muscle’s demands -- and that can be useful for athletes, too. If you’re doing interval training, for example, you might want to see spikes of lactic acid – to show you’ve pushed your body hard. But on a long, gentle jog, keeping lactic acid levels low can help avoid cramps and muscle fatigue.

And someday, sweat-sniffing wearables might be useful for people with diabetes or cystic fibrosis -- or anyone else who could benefit from monitoring the molecules in their sweat. Before they release this thing to the general public, though, the team wants to increase the range of substances it can detect -- and make it even smaller. Their current prototype is about the size of a wristwatch, but they hope to shrink it down onto a single chip that would be easy to fit into the kinds of exercise wearables that already exist. So it might not be long before you get more up-close and personal with your sweat than ever.

Now, generally, super-charged sensors are the kind of thing that you’d want to keep around -- even if your New Year’s resolution to actually hit the gym this year has well and truly disintegrated. But there are some kinds of devices that -- well, it would be great if they dissolved. Like the ones that doctors only need to keep in patients’ brains, but only for a few days. That’s why engineers from the University of Illinois teamed up with brain surgeons to develop a tiny sensor that tracks the health of people with brain injuries … and then just vanishes away.

Traumatic brain injury is caused by a serious blow to the head. One and half million people in the US suffer this condition each year, and fifty thousand of those people die. Gunshots, falls, and car accidents are the top three causes, and young people and the elderly are the most at-risk. It’s especially dangerous, because even if a patient survives the initial impact, complications afterwards can completely disrupt the recovery process. One of the biggest concerns is brain swelling after injury. The increased pressure restricts blood flow and the vital oxygen that comes with it. If it’s not dealt with immediately, the brain could be permanently damaged.

So patients’ brains need constant monitoring after a big head injury, and that’s where this new micro-sensor comes in. It’s a small flat rectangle made mostly from silicon and magnesium encased in a biodegradable coating -- so dainty it could fit comfortably on your little fingernail. Once it’s inside the skull, this little thing can work as a pressure or temperature sensor, sending information to an external device. And after a few days, it just degrades, absorbed by the body -- which isn’t as dangerous as it might sound, because silicon and magnesium are common substances the body can easily handle, especially the tiny amounts in the device.

This chip would be a big improvement on the sensors doctors use now, which need to be surgically removed after the patient has recovered – something I imagine zero people want to deal with after a traumatic brain injury. So far, the device has only been tested in rats, but the researchers will soon be trying it out on pigs to make sure the device is completely safe before they test it on people.

Beyond pressure and temperature, the researchers are also experimenting with biodegradable sensors that measure acceleration, acidity, and fluid flow -- all useful things to know about a brain that’s just been knocked around. That info helps doctors understand what’s going on inside in their patients’ heads -- literally -- and help make better choices for their future care. So a new generation of tiny sensors that can dissolve in patients’ bodies should be a pretty big deal.

Thanks for watching. If you want to hear about some of the biggest-ever news when it comes to our solar system, check out this episode over on our SciShow Space channel, where we explain the real story behind the new ninth planet. No, it is not Pluto. And don’t forget to go to youtube.com/scishow and subscribe!

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