The All-Devouring Blob

I might be a bit late to the party, but I just saw this the other day:

Holy Tokyo-devouring B-movie blob, Batman! That is awesome! You can check out the clip here: http://www.youtube.com/watch?v=LcQ3GWpy22Y

I’m a little curious how they get the magnetic cube sitting there at the start. Maybe using a magnet underneath the table to hold it in place until the devouring begins? Minor details. 

We’ve clearly got some iron-infused Silly Putty having some fun here. I’m a big fan of Silly Putty, even the non-magnetic sort. We use it in our elementary/secondary school science demos for blowing kids’ minds. If you haven’t played with Silly Putty before (you poor soul…you should stop reading and go get some right now), I’ll tell you how.

The question is whether Silly Putty is a solid or liquid.  First you rip it:

Looks pretty solid to me. It also follows the basic definition of a solid: a material that keeps its own shape. But the real common sense clincher? I’ve certainly never been able to rip water. Solid.

Then you sit the putty on the edge of desk and come back a bit later to find this:

Credit same as above.

Liquids: they fill the shape of the container they’re in. And if that container is shaped like “there’s the edge of a table, and there’s the floor and oh geez cat, don’t knock that glass over!“, well, that’s where it flows. Now tell me that doesn’t look like a liquid.

The mind blowing works best with 4th/5th graders I’ve found, who have a strong feeling for solids and liquids, are certain that one cannot be the other, and aren’t yet too-cool-for-school like high schoolers (for them we save liquid nitrogen for the mind blowing).

Silly Putty can be both a liquid and a solid because it’s a cross-linked polymer. Which really just means it’s a bunch of veeeerry long molecules (polymers) that are anchored to each other. If you anchor the molecules just right, you can get some really wild physical properties – like the ability to confuse the heck out of people who thought they knew what liquids and solids were.

On really short time scales (like bouncing or ripping), it looks like a solid since the long molecules don’t have time to untangle themselves from the knotted ball of molecular yarn. At long time scales (like sittin around on the desk), those molecules can untangle a bit and move around and do liquid-y things. We call these sorts of materials viscoelastic – “visco” because they can be like a viscous fluid, and “elastic” because you can bounce them off your brother’s head. They’re very cool materials and very useful (helmet padding, car bumpers, wrestling mats…).

So the all-devouring blob? At long time scales, like the 1.5 hours making up that gif, the putty can flow around the magnetic cube like a liquid and get all of it’s metal-attracting bits as close to the cube as possible.  And it’s next stop after that? Tokyo.

 

What’s cooler than being cool?

One acceptable answer to the title question comes, of course, from Outkast.  The other comes last week from Simon Braun and Dr. Ulrich Scheider’s group at Ludwig-Maximilians-Universität, who finagled some potassium atoms until they were colder than absolute zero.  I’ll let that sink in.  Colder than what is the coldest temperature possible.

As the Governator once said: Alright everyone, chill!

Your first reaction is probably: ….what.  That doesn’t make any kind of sense.  Isn’t absolute zero the temperature where all atoms and particles just freeze solid?  No more motion, no more energy.  How can you get colder than that?  To answer that, it helps to remember what temperature is, from a physics perspective (instead of maybe a smartphone app perspective).  Temperature is really just a number representing how much energy a system has.  Are the atoms bouncing and flipping out like a Jackie Chan flick?  High temperature.  Are they slow and solid enough to build a snowman out of?  Low temperature.  But usually it’s not that simple.  Even at one specific temperature, say 27.2F (the temperature outside my apartment right now), a small handful of atoms (or particles or molecules) have high energy, while most of them have lower energy.

The atoms in that snowflake definitely aren’t Jackie Chan.

Here’s a useful analogy: the majority of people across the world are lazy.  The Elon Musks and Tina Feys and Ghandis are very rare.  Probably why we find them impressive and inspiring and hilarious.  On a given night, most people would much rather grab some drinks, lounge on the couch, and catch up on Netflix than, say, assemble a massive undertaking to solve the unsolvable inequalities of the world.  Small atoms are the same way.  The vast majority of them are in the lowest energy state – passed out with bowl of cheetos in their cozy electron blankets, if you will.  Then there are a few rare ones that jump up and do a Robin Williams routine.

[[WARNING: There’s going to be an equation at the end of the next paragraph.  I’m warning you ahead of time so no one freaks out.  It’ll be ok.]]

The distributions of those energy states – the number of atoms which are lazy and the number which are amped up – follow a very specific pattern.  Physicists have come up with some pretty handy formulas that describe those numbers very accurately, an area broadly called statistical thermodynamics.  Here’s a general equation (the one I warned you about!) for one of those distributions:

n ∝ exp⁡(-E/(kB*T)) 
The Boltzmann Distribution!

I’ll give you time to get blood flowing back through your fainted grandmothers.  Good?  The details of the equation aren’t important.  But what is important is to notice is that the number of atoms with a certain energy, the symbol n, depends on temperature (plus a bunch of other things) which I highlighted.  Bringing it back full circle, this a way we can unambiguously define temperature.  It’s the quantity that gives a bunch of particles their specific energy.  If you’ve got more high energy Robin Williams-particles, that’s a higher temperature.  A very convenient side effect is that now you’ve also got a number to tell your friends to let them know how blisteringly cold it is in the morning.

Back to Simon Braun and colder-than-absolute-zero potassium.  What he and his group did was get some potassium atoms good and frosty while trapping them in a very high energy configuration.  For this part they got to use all sorts of cool-sounding physics tools like anti-traps and superfluid transitions.  So they now had very cold atoms, trapped in a high-energy phase.  Now the exact details of what happened next are beyond me, but as I can figure it, they could use what they knew about the distribution of energy (a cousin to the equation above) to figure out what statistical “temperature” defines such an arrangement.  And lo and behold: less than absolute zero!

At this point it’s tempting to get a little agitated.  “Hey, that’s just splitting hairs over how you define temperature!”  I know I wanted to at first.  But when you realize that this result comes from what thermodynamics tells us temperature physically is, it opens up some really fascinating questions about how quantum things (the very smallest, seemingly most basic particles you can have) play nice or don’t play nice with the way we understand thermodynamics.

Regardless, someone needs to get Outkast on the phone and tell him to write Hey Ya v2.0.

Touch me, touch me

Benjamin Tee from Zhenan Bao’s group at Stanford recently put out this research article on self-healing electronic “skin”:

http://www.nature.com/nnano/journal/vaop/ncurrent/full/nnano.2012.192.html

Oooh! Ahhh! What might someone use this for? Robots we can torture, obviously! (As illustrated by the fantastic Sci-ence comic blog.) Because I’m working on flexible electronics, my mind goes straight to consumer gadgets too. This sort of material is the sort of thing you bet Apple or Samsung would pay a pretty penny for once they eventually get the roll-up foldable tablet computers into the hands of folks with little kids who would like to pull on them. Or dogs. Not kids pulling dogs, but dogs pulling things, 21st century edition: The Dog Ate My Transparent Rolled Up Data Pad. But not with this baby. Just stick the halves back together, hold for a few seconds, and voila! Good as new, according to the data here. I can see the B-roll on the late night commercials now.

The “skin” part of the work comes from the fact that the material is also pressure sensitive. As a number of folks have pointed out, that could really benefit materials for high tech prostheses too.

Look at these poor robots, with their tough and rigid skin.  So last century.

It’s also worth mentioning that the conductive part of the skin comes from microscopic nickel particles.  Nickel, of course, being the winner of the much under-reported “Allergen of the Year” award in 2008. I can’t see that being an issue for our eventual self-repairing soft-skinned android overlords.

Who wants some infographics?

Nanotechnology is a pretty big deal these days. Not only is it a huge buzzword for science grants, I also end up talking in nanoscale pretty much everyday (yesterday for example: “Ok, that film needs to be thinner than 150 nanometers”). It recently hit me that I have a very hard time conceptualizing what a nanometer actually is. Sure, I know it’s about 50,000 times smaller than the width of a single hair, but so what? Like “a billion”, it really doesn’t mean anything to me.

So inspired by that really cool star-size comparison I’m sure everyone’s seen, I decided to make one for small stuff. I’m no graphic artist, so it isn’t too pretty, but it works. It’s just as much for my own edification than for anyone else, but it might be fun to look at.