[ INTRO ] Science fiction is famous for predicting, if not outright inspiring, the invention of some pretty awesome technologies.

Like long-distance video  conferencing, digital tablets, or a liquid metal robot that’s  sent back in time to assassinate a rebellious teen before he leads  humanity against a robot uprising. And I know what you’re thinking.

No, scientists did not just invent time travel. This week, a proof-of-concept study  published in the journal Matter showed off a new material that might give  rise to a new class of liquidy robots. The hard bodies of traditional robots limit what they can do and where they can fit.

So over the last few decades, we’ve seen the rise of soft-bodied robots. These robots can deform their bodies  to move in a bunch of different ways… swimming, climbing, rolling, and  jumping their way to get a job done. Some can even shapeshift between  several different predetermined shapes.

But since they’re still solid, they can not fit through openings  smaller than their bodies. If we needed a soft-bodied robot to, say, make its way into a hole a  couple of millimeters wide to tighten a bolt on the inside of a  machine without completely disassembling it, we would be out of luck. So for the past few years, scientists have been playing  around with liquid-based robots.

These guys can fit almost anywhere, by squishing down, stretching out, and even splitting into multiple  streams and then coming back together. But a liquid robot’s greatest strength is also its greatest weakness. Liquids can’t take much  pressure without deforming, so while they can get almost anywhere, they’re pretty weak, which limits  what they can do once they get there.

So an international team of engineers  developed a new liquid robot, mixing in solid, microscopic, magnetic particles to get the best of both worlds. They call it magnetoactive phase  transitional matter, or MPTM. By using magnets to push and  pull the magnetic particles, MPTM can shapeshift to perform tasks in the same way some soft robots do.

And much like the T-1000 from Terminator 2, it can also change from solid to liquid and back. See, the liquid metal the team used is gallium. And at sea level, gallium melts just before  its temperature hits 30 degrees Celsius.

In other words, its melting point is high enough for it to stay solid in your typical room, but low enough to melt in the palm of your hand. In order to get the gallium  to melt whenever they want, the team controls its temperature  by exposing it to a magnetic field that keeps flip-flopping the  direction it’s pointing. That causes all the magnetic  particles suspended in the gallium to collectively flip flop as well.  And all that movement creates heat.

So while it’s exposed to this magnetic field, the temperature inside the robot becomes  hot enough for it to melt and stay liquid. Then, the team can use magnets to push  or pull it wherever they want it to go and in whatever shape it needs to be in. And when they need it to be solid, they just turn the field  off and wait for the metal to cool back down like hot things do.

Now, this MPTM isn’t the first  solid-to-liquid transitioning material, but past attempts were like a lot more goopy. And that lack of fluidity  limited their usefulness. While testing their new  kind of liquid metal robot, the researchers were able to solder a  small LED into a hard-to-reach circuit by having it act as a universal screw.

The robot melted down, filled a threaded hole, and then solidified to hold  two plastic plates together. Kind of a single-use robot, but hey. It did get the job done.

They also demonstrated MPTM’s  potential as a medical device. In one test, they had it enter a  fake stomach in its solid form, liquefy to surround a foreign  object, and solidify to grab hold. Then, some magnets outside the stomach guided the whole kit-n-kaboodle right on out.

In another, they had it grab a drug, go to a  specific target location in the fake stomach, liquefy to release the drug in  that location, then skedaddle. Now, the internal temperature of a live, human body is well over the  melting point of gallium. So if this ever became an  actual medical procedure… one that I would very much  prefer to be asleep for… we would need to use a different metal.

Luckily, the team already has  their sites set on a gallium alloy that can stay solid inside  a human when it needs to. Finally, there was the prison break! They made a tiny human-shaped MPTM  robot and stuck it behind literal bars.

It was able to melt down, trickle out of its cell, and retake its human shape, all in less than 10 minutes. But don’t worry I’m pretty sure Liquid  robot assassins are still a long way off. Probably.

In the meantime though, MPTM might be used in a range  of fields that require specific, precise actions in hard to reach places. And it’s all thanks to magnetism. In other magnetic news, the Earth’s solid metal inner  core seems to have hit the breaks on its rotation rate, according to a study  published this week in Nature Geosciences.

If that just set your internal  disaster movie alarm bells a-ringing, you can go ahead and dampen them. This is probably a thing that has  happened many, many times before. There are two parts to the Earth’s core.

The inner core is surrounded  by a liquid metal outer core, which is churning all around and creating  the planet’s protective magnetic field. And since the inner core is chock full of iron, those magnetic forces are thought  to mess with its rotation rate. In fact, the inner core rotates entirely  separately from the rest of the Earth.

And how fast it rotates varies. Since at least the mid-1990s, scientists have been measuring  how long it takes seismic waves to pass through the planet. They noticed that waves which start  and end at the exact same places don't always take the exact same  amount of time to get there.

Some scientists have suggested that this is due to changes in the size of the inner core, but more recent research seems to  suggest it’s about changes in spin. Turns out, if the inner core is  spinning a little faster than usual, any seismic wave that tries to pass  through it will get a little speed boost. And when the core is spinning a little  slower, it takes a little longer.

So to study how the inner core’s  rotation has changed over time, researchers in China dove  into the seismic records, starting with the past three decades. They looked at two types of seismic waves, which take different paths through the inner core. And because they take different paths, they don’t get the same  speed boost on their way out.

So the greater the difference  in their total travel times, the faster the inner core is spinning. . And the team discovered that from  the early 1990s up until 2009, the average difference was dropping. And ever since 2009, the difference in  travel times has stayed pretty much constant.

They took that to mean that the inner  core started spinning more slowly in the years leading up to 2009, and then it…stopped. Well, not stopped stopped. It stopped  spinning faster than the rest of the Earth.

But 30-odd years is nothing  on the scale of human history, let alone Earth’s, so they went back to the records. And they found the same pattern  occurred in the late 1960s. The core’s rotation slowed down  for a few years to the point where it was briefly spinning  slower than the rest of Earth.

Or from a certain point of view, it’d  look like it was spinning backwards! So the team thinks that between 2009 and 2011, we went back to living in a world  where the inner core is a slowpoke. But there’s nothing to worry about.

In fact, they think the inner core  swings between spinning faster and slower than the rest of the  planet every 30 to 35 years or so. Now it’s tough to be certain. We don’t have data going back further in time that can definitively confirm the pattern.

But we do know that global temperatures, the Earth’s magnetic field, and the length of the day go  through cycles of a similar length. So with more research, the team  proposes we might one day learn that all of these things are actually connected. It’s just another piece in  the puzzle that shows us just how complex this big ball of rock  and metal and cute fluffy animals is.

Thanks for watching this episode of SciShow News. And thanks especially to our patrons  who help keep our world spinning here at Complexly and at Scishow. If you’d like to learn more about ways that you can help support the channel, you  can head on over to patreon.com/scishow.

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