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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,
liquify 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,
liquify 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.
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