May 26, 2023 • 31 mins
Temple University scientists have found a new way to improve chocolate and it involves electric fields. Learn about the technology and physics behind improving a nearly perfect food.
See omnystudio.com/listener for privacy information.
Mark as Played
Transcript
Episode Transcript
Available transcripts are automatically generated. Complete accuracy is not guaranteed.
Speaker 1 (00:04):
Welcome to tech Stuff, a production from iHeartRadio. Hey there,
and welcome to tech Stuff. I'm your host, Jonathan Strickland.
I'm an executive producer with iHeartRadio. And how the tech
are you? It is time for a classic episode of
tech Stuff. This episode originally published way back on July sixth,
(00:29):
twenty sixteen. Really, I probably should have published this one
on Valentine's Day now that I look at the topic.
The topic is how tech could make better chocolate. Let's listen.
In so, a consulting firm working on behalf of Mars Incorporated,
which is a giant candy company that makes a lot
(00:52):
of different chocolate products. This consulting firm went to a
group of physicists at Temple University, and physicist is one
of those words I have difficulty pronouncing. I think I
might just say scientists. Scientists at Temple University. Hey, that's
way better. And these guys had developed a method to
make crude oil flow more easily through pipes using electric fields.
(01:16):
So the question that the consulting firm had was could
you do the same thing you did for crude oil
for chocolate? And here's a spoiler alert, yeah they could,
but I want to talk more about what they did
and how they did it because it's a really interesting story.
So I'm going to go into a bit more detail
(01:36):
about the physics and the technology behind the scientist solution
for this problem. It's pretty cool, and a lot of
it was stuff I had no idea about before I
began to research the story. So today's episode is going
to be about chocolate. It's going to be about viscous fluids,
about electroreological fluids and how an electric field can change
(01:58):
their fluidic properties, specifically viscosity. So yeah, this episode's going
to be science heavy, but there's also chocolate, so stick around.
You know, everyone loves chocolate. So let's get into the
physics first. Now, fluid dynamics is pretty complicated, and also
there's some stuff that's related to this that falls into
(02:18):
the category of misinformation about viscosity. So I'll be talking
a lot about not just the principles in general, but
some specific myths that I would like to bust as
some of my former coworkers used to do on a
regular basis. So, first of all, viscosity is a property
(02:39):
of fluids or semi fluids, and it can be described
as a fluid's thickness or stickiness, and its resistance to
flowing due to internal friction. More accurately, viscosity is a
measure of the resistance of a fluid's deformation due to
tensile or shear stress. Now, sheer stress is mechanical stress
(03:00):
that's parallel to the surface of that substance. So you
could think of sheer stress as it's not perpendicular. It's
not like an impact, right, It's more of a tearing
tenstyle stress is a pulling stress rather than a compression stress,
So again, instead of compressing stuff closer together, it's about
(03:22):
pulling stuff further apart. And water has a pretty low viscosity.
Honey has a very high viscosity. So we actually measure
viscosity in units called poises poises. Water at room temperature
twenty degrees celsius or so has a viscosity of zero
point zero one poises or acenti poise. In other words,
(03:47):
a thick oil might have a viscosity of one point
zero poise. Now we measure viscosity with a viscometer. I'm
not making that up. It's actually the name of the
tool used to measure fluid's viscosity. Now, typically we will
call a liquid viscous if its viscosity is higher than
(04:08):
that of waters, and if the viscosity is lower than
that of waters, because water is not the least viscous
material that we know of, if it has a lower viscosity,
then water we call that fluid mobile. So some fluids
are so viscous that they can actually seem to be
a solid, And this leads us to that misinformation I
(04:29):
was talking about. It's one of those things that I
hear bandied about pretty well, not as frequently as it
used to, but it's one of those mis understandings that
gets passed around as fact every now and again. And
that is the idea that glass is one of these fluids,
that glass is actually a fluid that is so viscous
(04:51):
that it appears to be a solid, And that is
not true. Glass is not a very, very viscous fluid.
It's a little more complicated than that. So here's the
basic idea. People have noticed that if they look at
windows and very old buildings like medieval churches, they see
(05:12):
that the base of the window is thicker than the
top of the window. And this has led some people
to conclude to jump to a conclusion that the reason
why the base is thicker than the top is that glass,
over the course of centuries has been flowing downward, and
(05:33):
that it's so slow that it's not detectable under normal situations.
It's only over the course of centuries that you can
see the difference. Here's the problem is that that's just
not that's not the case. That's not true, it's not
what's happening. If you look at the glass making approach
(05:55):
in the Middle Ages, you'll see why there's a thicker
part of the paine of glass. Glass was created generally
speaking in the Middle Ages through something called the crown
glass process. It's a pretty neat idea pretty neat way
of making glass windows. Here's how it worked in general. First,
(06:15):
you get your raw materials to make glass, and in
the Middle Ages that was essentially sand and potash, and
you mix it together and you melt them in a
very hot furnace. Then you would get a glass blower
with a pipe and they would get a roll out
a lump of molten glass put on the pipe, blow
(06:36):
out the glass, so they expand the glass outward before
flattening it. So they don't just you know, create a
globe of glass, They actually flatten it back out. Then,
with the flat glass, which is still hot and still malleable,
it hasn't cooled to the point where it is really solidified,
you would put that on a disc, a spinning disc,
(06:56):
and the disk spins around to draw out the glass
to flatten it further. Sort of like how a pizza
maker will toss and spin dough in the air in
order to make that circular pizza. It's kind of similar
to that. So the disk spins and the centripetal force,
if you like, is pushing the glass outward toward the edges.
(07:17):
So then once that's done, you would cut the glass
into panes so that you could fit them in a window. Now,
that would mean that when you would get anywhere close
to where the edge of the glass was, the outer edge,
because you put the glass on that disk and you
spun it around, the outer edge was thicker than the
rest of the glass, just because that's where the excess
(07:40):
was accumulating as it was being pushed outward due to
the spinning motion. So typically window makers would cut panes
so that a thicker edge would only be on one
side and they'd put that side at the bottom at
the base of the window, so glass didn't flow to
the base. Hundreds of years it started out like that.
(08:02):
It was like that from the beginning. That being said,
glass is a really interesting substance. It's what we would
call an amorphous solid, so saying that it's a fluid
or a liquid is not accurate. But it is an
amorphous solid, which is a little hinky compared to other
materials that you might be familiar with. So typically not everything,
(08:26):
obviously metals and glass being exceptions, but a lot of
solids have an ordered crystalline structure, so that means the
molecules are organized in a pretty regular lattice. They form
a nice repeating pattern that goes throughout the entire material.
When you heat up this solid, those molecules start to
(08:49):
shimmy and shake, some of the molecular bonds might start
to break down a little bit, the bonds between one
molecule and another. The essentially the crystalline order breaks down,
and if you heat a solid beyond its melting point,
the crystalline structure completely breaks down and molecules will begin
to flow freely, or as freely as the viscosity of
(09:09):
that fluid allows and there's a very clear delineation between
the solid and liquid stages. You can see the difference
molecularly from the way this substance looks when it's in
solid form versus in liquid form, and we call that delineation,
that border between the two the first order phase transition.
(09:32):
It's obvious when you look at it from a microscopic standpoint.
I mean it's obvious from a macroscopic standpoint two, because
a solid behaves one way and a liquid behaves another way. Now,
when you cool a liquid down, its viscosity tends to increase.
If you introduce a nucleation site into the liquid, crystals
(09:54):
can form and you get that nice solid structure again
once you get down below what the melting point was.
But glass doesn't do this. Glass doesn't form a crystalline structure.
Glass's viscosity increases, so it does what other fluids do
at that point. But since it doesn't crystallize, it solidifies
(10:17):
in a different way. The molecules actually form an irregular arrangement,
not that nice ordered structure that you see in other solids.
But that irregular arrangement is still cohesive enough to maintain rigidity.
So glass does become a solid, it's just not a
crystalline solid. It's an amorphous solid. We'll be back with
(10:39):
more about how technology could make better chocolate after these messages. Now,
there's no first order phase transition here. It's not like
if you looked at the liquid form of glass and
the solid form of glass, you would a massive difference
(11:01):
in the molecular structure. But there is a second order transition.
Now that transition is a little more subtle than first
order transitions. It involves the thermal expansion and heat capacity
of a material, so it wouldn't be as obvious to
casual observation on a microscopic level, but there would still
(11:24):
be differences with the thermodynamics of the material, so we still
would say the glass is a solid, not a liquid.
All right, I'm done with glass now, I promise. I
had to go on that little track just because it
was related to the stuff I was talking about, and
I get really irritated seeing that one myth passed around
as fact. So now you know, if you ever go
(11:44):
through a tour and the tour guide says and the
reason that the windows are thicker at the bottom is
because glass flows over the course of hundreds of years.
You can raise your hand and say, well, actually and
tell them Josh Clark sent because I don't want that
kind of burden on me. I like being able to
take tours. Anyway, Let's get back to viscosity in general. So,
(12:07):
like I said earlier, viscosity is due to internal friction
of a liquid. And you might think that that sounds weird,
like how can a liquid have friction inside of it?
But we're talking about liquid specifically that have like molecules,
and those molecules can have a tendency to resist getting
by each other. So some molecules are more resistant to
(12:29):
slip and by each other than others. Or a liquid
could actually have particles that are suspended in it. It could
be a suspension, which is different than just a pure liquid.
But if it's a suspension, it's got particles suspended within
the liquid at some level of density, right, Like some
may be a pretty weak suspension where you don't have
(12:50):
a whole lot, but others could have a greater density
of particles inside a suspension of fluid. Make chocolate bars, say,
and you're laying out melted chocolate into the mold for
the chocolate bars, and it clogs up, and you have
to stop production and clean out the clog and get
everything back up to temperature and start it all over again.
(13:13):
It's time consuming and expensive when that happens. So one
solution to preventing it from happening is dilute the cacao
more so that those particles don't clump up as much
because there's a less dense CACW component in the fluid.
That essentially means replacing CaCO with something else, typically something
(13:36):
that is less viscous, like that oil that fat essentially,
so you usually add more fat to the recipe so
you get the more fat but less cacw. However, it
ends up flowing better and creates the chocolate bars that
you want without creating the clogs. But it's not necessarily
(13:56):
the best product you could create. It's just the most
convenient upon the method of production. So that's where this
alternative solution comes in. If you could change the shape
of those cacal particles in the fluid so that they
packed together more effectively, you would reduce that viscosity, that
(14:16):
internal friction of the fluid. So imagine you've got one
of those inflated rubber balls, like a kickball or something. Now,
imagine that you're able to grab hold on either side
of this ball and pull it outward so that you're
elongating it. Now it would become a more of an
(14:37):
oval shape, or as the researchers at Temple University called them,
prolate spheroids. Now, the interesting thing about these prolate spheroids
is if you align them in the direction of the
flow of chocolate, you can pack more of them together.
They have these elongated sides, and they will fit together
(14:57):
much more snuggly. You can create chains of them, and
chocolate would flow much more readily. But how do you
change the shape of those cacal particles. What is it
that you could do to make them actually assume a
different shape than their natural globular ball like shape. This
(15:19):
is where electric fields come in. We're going to talk
about applying magnetic or electric fields to a fluid to
change its viscosity. But first, this doesn't work with every fluid.
Not every fluid reacts to electric fields and magnetic fields
in a way that will alter its viscosity. But it
does work in fluids that have certain non conducting or
(15:41):
weakly conducting particles suspended in an electrically insulating fluid. Now
we call this a special type of liquid electroreeological fluid
electroheological fluids. That essentially means that when you apply an
electric or magnetic field to such a fluid, it changes
its viscosity. Sometimes we also call them smart fluids, but
(16:04):
more about that in a bit. Now. Interestingly, the property
was completely discovered by chance. There was an inventor named
Willis Winslow who observed the effect in the nineteen forties,
and he actually patented it in nineteen forty seven. Now,
for this reason, we sometimes call this effect of changing
an electroheological fluids viscosity the Winslow effect, And I'll mostly
(16:29):
be using that term from here on out, because there's
only so many times I'm going to be able to
say electroreeological before my mouth just decides to rebel against
the rest of me and march out the door. And
as entertaining as that would be, I kind of need it. Well,
we know that the candy man can make better chocolate,
(16:51):
but how could tech make better chocolate? I guess we'll
conclude that when we come back from these messages. All right,
So Applying an electric or magnetic field to such a
(17:14):
fluid changes that fluid's viscosity within melliseconds like it's practically instantaneous,
And if you remove the field, the particles in the
fluid will snap back to their original shape, to the
fluid's viscosity will return to what it normally would be.
So the change isn't permanent. It only persists as long
(17:34):
as the respective field persists, which is super cool because
you can do these temporary changes that are really useful
in specific situations and then have it go back to
normal and it's like it never happened in the first place.
But one thing to keep in mind is the direction
of the electric or magnetic field is critically important when
(17:57):
you want to make a particular effect. So in the
case of chocolate, if you apply the electric field perpendicular
to the direction of flow, you will actually increase the
viscosity of the chocolate. You will make it thicker, more
like a gel. Melted chocolate will turn into this kind
of thick gel. It'll otherwise have all the same properties
(18:19):
that had before, but that viscosity will increase dramatically. However,
if you were to apply that electric field in the
direction of the flow of chocolate. Then you would decrease
the viscosity of chocolate and it will flow more freely
at that point. Now this makes some sense because imagine
that you have these elongated ovals, these prolate spheroids. Right.
(18:47):
If you stand them vertically, then you could imagine them
slipping through a pipe very easily. If you laid them
out horizontally, you could imagine them ending up like blocking
pipe easily. Because it's like trying to fit a long
stick through a narrow doorway. If you don't turn it
the right way, you're just gonna hit against the door.
(19:08):
This is making me think of my dog, Timbalt, who
has done this on numerous occasions. He just he can't
get it through his little doggy mind that he needs
to turn the stick vertical in order to move it
through a doorway. He just wants to charge ahead full
steam with the stick horizontal. In many other ways, He's
(19:28):
an intelligent dog, so we forgive him this lapse of judgment. Anyway,
the chocolate on a molecular level is essentially the same thing.
If you are applying this electric field perpendicular to the
flow of chocolate, then you get this much thicker mixture.
And an interesting side note, the electro rheological properties of
(19:49):
chocolate aren't a new discovery, right. I mean, I covered
this story for house Stuffworks now because there was a
new application of this property with chocolate. But we actually
knew that chocolate would react this way already, at least
to the point of increasing the viscosity, because back in
nineteen ninety six there was a Michigan State University grad
(20:12):
student who observed the Winslow effect on chocolate. And his
name is doctor Christopher R. Daubert, and as professor, doctor
James Steph worked with him. They both conducted experiments on
liquid chocolate and observed the Winslow effect. Now, in that experiment,
Daubert was again increasing the viscosity, not decreasing it, so
he was turning chocolate into that thicker gel. That the
(20:34):
liquid chocolate into thick gel. It wasn't until recently that
we saw someone try and do the opposite. So that
brings us to the Temple University experiment. So you had
these researchers. They had worked on crude oil and decreased
the viscosity of crude oil, which is a huge thing
for the oil industry to be able to move oil
(20:57):
more effectively without the fear of clogs or viscosity screwing
up things that had been planned ahead of time. They
wanted to see if they could, in fact use a
similar approach to have liquid chocolate move more smoothly through
a system, so that manufacturers could save money by not
(21:17):
having to worry about cleaning up clogs and shutting down
production for maintenance. So they had to test this hypothesis
that an electric field directed in the flow of liquid
chocolate would reduce viscosity. So they built a cool chocolate
zapping gadget. It's not really a zapper, it's a it's
(21:39):
kind of not entirely accurate, but I like the idea
of using electricity to zap chocolate to make it better.
That's just an oversimplification of what happened, but that's okay.
I'll explain to you what was actually going on. They
built this thing where it starts with a bit of
a melting chamber. You can just think of it as
(21:59):
like a a pot. It could even be a glass vial. Really,
it could just be any little container that can hold chocolate.
They put the chocolate in the container, and they cover
the container, sealing it shut. They added compressed nitrogen gas
into the chamber simply really to just increase the pressure
(22:20):
inside the chamber itself. The chamber was heated so that
you had chocolate melting into a liquid. There was a
therma couple in there to make sure that the temperature
was correct so that the chocolate would not overheat or
cool down so much that it becomes solid again. And
then the base of this container was essentially a drain,
so there's like a hole at the bottom of the
(22:43):
container that liquid chocolate could flow through. Attached to that
was a tube, and inside the tube they put a
series of metal mesh screens, and the screens were what
generated the electric field. They had electricity running to those
screens and creating electric field that way in the direction
of the flow of chocolate, so the chocolate would end
(23:06):
up flowing very smoothly through the tube and didn't have
any issues. At the other end, they had another vessel
container that the liquid chocolate would flow into, it would
cool down solidify. So once that liquid chocolate flowed through
into the collecting vessel and once it was free of
(23:26):
the electric field, the cacal particles they went back to
their original shape immediately. Again, they didn't have to transform
or anything. It wasn't a gradual process. They boop moved
back into those globe shapes that they typically are in,
and the chocolate cooled and solidified and was, to all
(23:46):
intents and purposes, indistinguishable from the chocolate that was being
fed through at the top at that top chamber. So
they were able to reduce the viscosity of the flowing
chocolate and to the point where it was no there
were no issues of clogging, it was perfectly fine. So
(24:07):
they were able to prove that their hypothesis was correct,
that in fact, this electric field applied in this way
would decrease chocolate's viscosity. Hooray. But there's more to it
than that. So this experiment was not just a success.
The researchers actually realized that it had a lot more
implications than just having chocolate flow freely through a machine.
(24:32):
That again, the reason why chocolate has such a relatively
high fat content is to create that oily fluid to
reduce viscosity, to have the cacao particles suspended within it
at a density that's low enough so that you're not
likely to clog up the machines. But if you use
this approach, if you use the electric fields to reduce viscosity,
(24:57):
you don't need as much oil or fat in your
chocolate content. You could actually start with a recipe that
has less fat in it, and the electric fields would
take care of the viscosity problem, so you don't have
to have as much fat there. That also means you
could have more cacal in your mixture. It could be
(25:18):
a higher proportion of the overall recipe. So they found
that they could reduce the fat content in certain types
of chocolate by as much as twenty percent and still
have no negative impact on the fluid's viscosity. Now, it
depends on what type of chocolate they were using. They
were actually using name brand chocolates, you know, like chocolate bars.
(25:43):
They would try different types and depending on the type,
they could actually end up removing up to twenty percent
of the fat in the mixture and still have the
chocolate flow without any problems. And beyond that, the researchers
said that people who are tasting the chocolate afterward, because
keep in mind, other than the fact that there was
(26:05):
less fat in it, there was really no difference between
the original chocolate and the end result. They said that
the end result chocolate actually tasted better to them. He said,
I had a more intense cacw flavor. It was more
chocolatey than the original chocolate. Now that could be just subjective,
or it could be purely psychological, but it's not outside
(26:27):
the realm of possibility that by increasing the proportion of
chocolate of cacao in your mixture because you've removed some
of the fat, so you've got more cacal per unit
of chocolate than you would previously, that you would also
affect the taste. It is entirely possible that that is true.
(26:50):
It hasn't really been tested on a scientific level. It's
mostly people saying, hmm, this tastes really good. Also, I
should mention this is not the same as fat free chocolate.
Fat free chocolate is essentially using some different type of
fluid other than oil to suspend cacal particles. So fat
free chocolate has that particular weird taste. It's not the
(27:14):
same as the stuff that Temple University was producing. So
I just want to clear that up. It's not like
you would take a bite of a brand new chocolate
bar that was made using this procedure and think, oh,
this tastes like fat free chocolate. No, So the end
result here is that we could end up with better
(27:34):
tasting chocolate with less fat in it in the future,
which seems pretty awesome to me. Now, earlier I mentioned
that electroheological fluids are also called smart fluids. That's because
these fluids can change their viscosity almost instantly in the
presence of an electric or magnetic field, and then go
right back to what they were before once the field
(27:55):
is turned off, and they become really important in ways
be on making superior chocolate. For example, car manufacturers have
been using smart fluids and suspension and braking systems. The
fluid can actually go from relatively thin to thick in
just a moment's notice, which makes it superior to a
lot of mechanical solutions that would take time to propagate
(28:16):
through a system. And you can have a variable suspension
in this way. Imagine that you have a suspension, it's
a fluid suspension, like literally, it's a suspension for a
car with fluid in it, not that it was a
fluid that has a suspension in it. It's kind of confusing,
so car suspension's got fluid in it. Very high end
sports cars have these, and you can set your suspension
(28:37):
to different modes, like you can predetermine which mode you
want at any given time. So let's say you're going
to be driving on like a racetrack, a nice smooth racetrack,
and you're really going to push the car to its limits.
You might want a pretty stiff suspension for that to
really be able to feel the car as you're driving
(29:00):
along this very smooth surface. But that stiff suspension would
be a torture device. If you were driving down a
normal everyday road that had some bumps and maybe some
potholes in it, that would be very jarring. You would
feel every single little bump. So in that case, you'd
want a more loose suspension, a little spring in it.
(29:23):
So you might want to reduce the viscosity of the
fluid inside the suspension to allow for more give really,
and you could do that with a smart fluid and
just change the electric or magnetic field that ends up
affecting the viscosity of the fluid. So you can actually
have settings and say I want a very stiff suspension
(29:45):
in this circumstance and so it generates the electric field,
the viscosity increases and you get your stiff suspension, or
you might say, oh, I want it to be a
more forgiving suspension, and it turns off that electric field.
The viscosity decreases and you have your more your suspension
when more given it. It's a pretty cool idea. I
chatted with Scott Benjamin about this before I came in here.
(30:08):
He was very interested when I started talking about chocolate,
but then when I started talking about smart fluids, he
really lit up because he knew exactly what I was
talking about. I mean, Scott is a car genius and
knows everything there is to know about cars, it seems.
So we had a good discussion about, you know, the
physical properties of smart fluids and why they behave the
way they do. So this technology could be used in
(30:30):
lots of different applications moving forward. When you can induce
some mechanical change in a fluid with something as simple
as an electric or magnetic field, a lot of different
opportunities open up. But for me, you know, I'm happy
with the chocolate thing. I'm going to settle for that
because I do love me some chocolate that wraps up
the classic tech episode of How Tech Could Make Better Chocolate.
(30:53):
Hope you enjoyed it. If you have suggestions for topics,
I should cover future episodes of tech Stuff a couple
different ways you can let me know. One you can
go on over to Twitter and you can send me
a message. The show's handle is tech Stuff hsw or
if you prefer, you can download the iHeartRadio app. It's
free to download. It's free to use. Navigate on over
(31:15):
to tech Stuff by putting that into the little search
field that I'll take it to the tech Stuff podcast page.
You'll see a little microphone icon. If you click on that,
you can leave a voice message out, but thirty second
ten length either way. I hope you're doing well and
I'll talk to you again really soon. Tech Stuff is
(31:37):
an iHeartRadio production. For more podcasts from iHeartRadio, visit the
iHeartRadio app, Apple Podcasts, or wherever you listen to your
favorite shows.
Welcome to tech Stuff, a production from iHeartRadio. Hey there,
and welcome to tech Stuff. I'm your host, Jonathan Strickland.
I'm an executive producer with iHeartRadio. And how the tech
are you? It is time for a classic episode of
tech Stuff. This episode originally published way back on July sixth,
(00:29):
twenty sixteen. Really, I probably should have published this one
on Valentine's Day now that I look at the topic.
The topic is how tech could make better chocolate. Let's listen.
In so, a consulting firm working on behalf of Mars Incorporated,
which is a giant candy company that makes a lot
(00:52):
of different chocolate products. This consulting firm went to a
group of physicists at Temple University, and physicist is one
of those words I have difficulty pronouncing. I think I
might just say scientists. Scientists at Temple University. Hey, that's
way better. And these guys had developed a method to
make crude oil flow more easily through pipes using electric fields.
(01:16):
So the question that the consulting firm had was could
you do the same thing you did for crude oil
for chocolate? And here's a spoiler alert, yeah they could,
but I want to talk more about what they did
and how they did it because it's a really interesting story.
So I'm going to go into a bit more detail
(01:36):
about the physics and the technology behind the scientist solution
for this problem. It's pretty cool, and a lot of
it was stuff I had no idea about before I
began to research the story. So today's episode is going
to be about chocolate. It's going to be about viscous fluids,
about electroreological fluids and how an electric field can change
(01:58):
their fluidic properties, specifically viscosity. So yeah, this episode's going
to be science heavy, but there's also chocolate, so stick around.
You know, everyone loves chocolate. So let's get into the
physics first. Now, fluid dynamics is pretty complicated, and also
there's some stuff that's related to this that falls into
(02:18):
the category of misinformation about viscosity. So I'll be talking
a lot about not just the principles in general, but
some specific myths that I would like to bust as
some of my former coworkers used to do on a
regular basis. So, first of all, viscosity is a property
(02:39):
of fluids or semi fluids, and it can be described
as a fluid's thickness or stickiness, and its resistance to
flowing due to internal friction. More accurately, viscosity is a
measure of the resistance of a fluid's deformation due to
tensile or shear stress. Now, sheer stress is mechanical stress
(03:00):
that's parallel to the surface of that substance. So you
could think of sheer stress as it's not perpendicular. It's
not like an impact, right, It's more of a tearing
tenstyle stress is a pulling stress rather than a compression stress,
So again, instead of compressing stuff closer together, it's about
(03:22):
pulling stuff further apart. And water has a pretty low viscosity.
Honey has a very high viscosity. So we actually measure
viscosity in units called poises poises. Water at room temperature
twenty degrees celsius or so has a viscosity of zero
point zero one poises or acenti poise. In other words,
(03:47):
a thick oil might have a viscosity of one point
zero poise. Now we measure viscosity with a viscometer. I'm
not making that up. It's actually the name of the
tool used to measure fluid's viscosity. Now, typically we will
call a liquid viscous if its viscosity is higher than
(04:08):
that of waters, and if the viscosity is lower than
that of waters, because water is not the least viscous
material that we know of, if it has a lower viscosity,
then water we call that fluid mobile. So some fluids
are so viscous that they can actually seem to be
a solid, And this leads us to that misinformation I
(04:29):
was talking about. It's one of those things that I
hear bandied about pretty well, not as frequently as it
used to, but it's one of those mis understandings that
gets passed around as fact every now and again. And
that is the idea that glass is one of these fluids,
that glass is actually a fluid that is so viscous
(04:51):
that it appears to be a solid, And that is
not true. Glass is not a very, very viscous fluid.
It's a little more complicated than that. So here's the
basic idea. People have noticed that if they look at
windows and very old buildings like medieval churches, they see
(05:12):
that the base of the window is thicker than the
top of the window. And this has led some people
to conclude to jump to a conclusion that the reason
why the base is thicker than the top is that glass,
over the course of centuries has been flowing downward, and
(05:33):
that it's so slow that it's not detectable under normal situations.
It's only over the course of centuries that you can
see the difference. Here's the problem is that that's just
not that's not the case. That's not true, it's not
what's happening. If you look at the glass making approach
(05:55):
in the Middle Ages, you'll see why there's a thicker
part of the paine of glass. Glass was created generally
speaking in the Middle Ages through something called the crown
glass process. It's a pretty neat idea pretty neat way
of making glass windows. Here's how it worked in general. First,
(06:15):
you get your raw materials to make glass, and in
the Middle Ages that was essentially sand and potash, and
you mix it together and you melt them in a
very hot furnace. Then you would get a glass blower
with a pipe and they would get a roll out
a lump of molten glass put on the pipe, blow
(06:36):
out the glass, so they expand the glass outward before
flattening it. So they don't just you know, create a
globe of glass, They actually flatten it back out. Then,
with the flat glass, which is still hot and still malleable,
it hasn't cooled to the point where it is really solidified,
you would put that on a disc, a spinning disc,
(06:56):
and the disk spins around to draw out the glass
to flatten it further. Sort of like how a pizza
maker will toss and spin dough in the air in
order to make that circular pizza. It's kind of similar
to that. So the disk spins and the centripetal force,
if you like, is pushing the glass outward toward the edges.
(07:17):
So then once that's done, you would cut the glass
into panes so that you could fit them in a window. Now,
that would mean that when you would get anywhere close
to where the edge of the glass was, the outer edge,
because you put the glass on that disk and you
spun it around, the outer edge was thicker than the
rest of the glass, just because that's where the excess
(07:40):
was accumulating as it was being pushed outward due to
the spinning motion. So typically window makers would cut panes
so that a thicker edge would only be on one
side and they'd put that side at the bottom at
the base of the window, so glass didn't flow to
the base. Hundreds of years it started out like that.
(08:02):
It was like that from the beginning. That being said,
glass is a really interesting substance. It's what we would
call an amorphous solid, so saying that it's a fluid
or a liquid is not accurate. But it is an
amorphous solid, which is a little hinky compared to other
materials that you might be familiar with. So typically not everything,
(08:26):
obviously metals and glass being exceptions, but a lot of
solids have an ordered crystalline structure, so that means the
molecules are organized in a pretty regular lattice. They form
a nice repeating pattern that goes throughout the entire material.
When you heat up this solid, those molecules start to
(08:49):
shimmy and shake, some of the molecular bonds might start
to break down a little bit, the bonds between one
molecule and another. The essentially the crystalline order breaks down,
and if you heat a solid beyond its melting point,
the crystalline structure completely breaks down and molecules will begin
to flow freely, or as freely as the viscosity of
(09:09):
that fluid allows and there's a very clear delineation between
the solid and liquid stages. You can see the difference
molecularly from the way this substance looks when it's in
solid form versus in liquid form, and we call that delineation,
that border between the two the first order phase transition.
(09:32):
It's obvious when you look at it from a microscopic standpoint.
I mean it's obvious from a macroscopic standpoint two, because
a solid behaves one way and a liquid behaves another way. Now,
when you cool a liquid down, its viscosity tends to increase.
If you introduce a nucleation site into the liquid, crystals
(09:54):
can form and you get that nice solid structure again
once you get down below what the melting point was.
But glass doesn't do this. Glass doesn't form a crystalline structure.
Glass's viscosity increases, so it does what other fluids do
at that point. But since it doesn't crystallize, it solidifies
(10:17):
in a different way. The molecules actually form an irregular arrangement,
not that nice ordered structure that you see in other solids.
But that irregular arrangement is still cohesive enough to maintain rigidity.
So glass does become a solid, it's just not a
crystalline solid. It's an amorphous solid. We'll be back with
(10:39):
more about how technology could make better chocolate after these messages. Now,
there's no first order phase transition here. It's not like
if you looked at the liquid form of glass and
the solid form of glass, you would a massive difference
(11:01):
in the molecular structure. But there is a second order transition.
Now that transition is a little more subtle than first
order transitions. It involves the thermal expansion and heat capacity
of a material, so it wouldn't be as obvious to
casual observation on a microscopic level, but there would still
(11:24):
be differences with the thermodynamics of the material, so we still
would say the glass is a solid, not a liquid.
All right, I'm done with glass now, I promise. I
had to go on that little track just because it
was related to the stuff I was talking about, and
I get really irritated seeing that one myth passed around
as fact. So now you know, if you ever go
(11:44):
through a tour and the tour guide says and the
reason that the windows are thicker at the bottom is
because glass flows over the course of hundreds of years.
You can raise your hand and say, well, actually and
tell them Josh Clark sent because I don't want that
kind of burden on me. I like being able to
take tours. Anyway, Let's get back to viscosity in general. So,
(12:07):
like I said earlier, viscosity is due to internal friction
of a liquid. And you might think that that sounds weird,
like how can a liquid have friction inside of it?
But we're talking about liquid specifically that have like molecules,
and those molecules can have a tendency to resist getting
by each other. So some molecules are more resistant to
(12:29):
slip and by each other than others. Or a liquid
could actually have particles that are suspended in it. It could
be a suspension, which is different than just a pure liquid.
But if it's a suspension, it's got particles suspended within
the liquid at some level of density, right, Like some
may be a pretty weak suspension where you don't have
(12:50):
a whole lot, but others could have a greater density
of particles inside a suspension of fluid. Make chocolate bars, say,
and you're laying out melted chocolate into the mold for
the chocolate bars, and it clogs up, and you have
to stop production and clean out the clog and get
everything back up to temperature and start it all over again.
(13:13):
It's time consuming and expensive when that happens. So one
solution to preventing it from happening is dilute the cacao
more so that those particles don't clump up as much
because there's a less dense CACW component in the fluid.
That essentially means replacing CaCO with something else, typically something
(13:36):
that is less viscous, like that oil that fat essentially,
so you usually add more fat to the recipe so
you get the more fat but less cacw. However, it
ends up flowing better and creates the chocolate bars that
you want without creating the clogs. But it's not necessarily
(13:56):
the best product you could create. It's just the most
convenient upon the method of production. So that's where this
alternative solution comes in. If you could change the shape
of those cacal particles in the fluid so that they
packed together more effectively, you would reduce that viscosity, that
(14:16):
internal friction of the fluid. So imagine you've got one
of those inflated rubber balls, like a kickball or something. Now,
imagine that you're able to grab hold on either side
of this ball and pull it outward so that you're
elongating it. Now it would become a more of an
(14:37):
oval shape, or as the researchers at Temple University called them,
prolate spheroids. Now, the interesting thing about these prolate spheroids
is if you align them in the direction of the
flow of chocolate, you can pack more of them together.
They have these elongated sides, and they will fit together
(14:57):
much more snuggly. You can create chains of them, and
chocolate would flow much more readily. But how do you
change the shape of those cacal particles. What is it
that you could do to make them actually assume a
different shape than their natural globular ball like shape. This
(15:19):
is where electric fields come in. We're going to talk
about applying magnetic or electric fields to a fluid to
change its viscosity. But first, this doesn't work with every fluid.
Not every fluid reacts to electric fields and magnetic fields
in a way that will alter its viscosity. But it
does work in fluids that have certain non conducting or
(15:41):
weakly conducting particles suspended in an electrically insulating fluid. Now
we call this a special type of liquid electroreeological fluid
electroheological fluids. That essentially means that when you apply an
electric or magnetic field to such a fluid, it changes
its viscosity. Sometimes we also call them smart fluids, but
(16:04):
more about that in a bit. Now. Interestingly, the property
was completely discovered by chance. There was an inventor named
Willis Winslow who observed the effect in the nineteen forties,
and he actually patented it in nineteen forty seven. Now,
for this reason, we sometimes call this effect of changing
an electroheological fluids viscosity the Winslow effect, And I'll mostly
(16:29):
be using that term from here on out, because there's
only so many times I'm going to be able to
say electroreeological before my mouth just decides to rebel against
the rest of me and march out the door. And
as entertaining as that would be, I kind of need it. Well,
we know that the candy man can make better chocolate,
(16:51):
but how could tech make better chocolate? I guess we'll
conclude that when we come back from these messages. All right,
So Applying an electric or magnetic field to such a
(17:14):
fluid changes that fluid's viscosity within melliseconds like it's practically instantaneous,
And if you remove the field, the particles in the
fluid will snap back to their original shape, to the
fluid's viscosity will return to what it normally would be.
So the change isn't permanent. It only persists as long
(17:34):
as the respective field persists, which is super cool because
you can do these temporary changes that are really useful
in specific situations and then have it go back to
normal and it's like it never happened in the first place.
But one thing to keep in mind is the direction
of the electric or magnetic field is critically important when
(17:57):
you want to make a particular effect. So in the
case of chocolate, if you apply the electric field perpendicular
to the direction of flow, you will actually increase the
viscosity of the chocolate. You will make it thicker, more
like a gel. Melted chocolate will turn into this kind
of thick gel. It'll otherwise have all the same properties
(18:19):
that had before, but that viscosity will increase dramatically. However,
if you were to apply that electric field in the
direction of the flow of chocolate. Then you would decrease
the viscosity of chocolate and it will flow more freely
at that point. Now this makes some sense because imagine
that you have these elongated ovals, these prolate spheroids. Right.
(18:47):
If you stand them vertically, then you could imagine them
slipping through a pipe very easily. If you laid them
out horizontally, you could imagine them ending up like blocking
pipe easily. Because it's like trying to fit a long
stick through a narrow doorway. If you don't turn it
the right way, you're just gonna hit against the door.
(19:08):
This is making me think of my dog, Timbalt, who
has done this on numerous occasions. He just he can't
get it through his little doggy mind that he needs
to turn the stick vertical in order to move it
through a doorway. He just wants to charge ahead full
steam with the stick horizontal. In many other ways, He's
(19:28):
an intelligent dog, so we forgive him this lapse of judgment. Anyway,
the chocolate on a molecular level is essentially the same thing.
If you are applying this electric field perpendicular to the
flow of chocolate, then you get this much thicker mixture.
And an interesting side note, the electro rheological properties of
(19:49):
chocolate aren't a new discovery, right. I mean, I covered
this story for house Stuffworks now because there was a
new application of this property with chocolate. But we actually
knew that chocolate would react this way already, at least
to the point of increasing the viscosity, because back in
nineteen ninety six there was a Michigan State University grad
(20:12):
student who observed the Winslow effect on chocolate. And his
name is doctor Christopher R. Daubert, and as professor, doctor
James Steph worked with him. They both conducted experiments on
liquid chocolate and observed the Winslow effect. Now, in that experiment,
Daubert was again increasing the viscosity, not decreasing it, so
he was turning chocolate into that thicker gel. That the
(20:34):
liquid chocolate into thick gel. It wasn't until recently that
we saw someone try and do the opposite. So that
brings us to the Temple University experiment. So you had
these researchers. They had worked on crude oil and decreased
the viscosity of crude oil, which is a huge thing
for the oil industry to be able to move oil
(20:57):
more effectively without the fear of clogs or viscosity screwing
up things that had been planned ahead of time. They
wanted to see if they could, in fact use a
similar approach to have liquid chocolate move more smoothly through
a system, so that manufacturers could save money by not
(21:17):
having to worry about cleaning up clogs and shutting down
production for maintenance. So they had to test this hypothesis
that an electric field directed in the flow of liquid
chocolate would reduce viscosity. So they built a cool chocolate
zapping gadget. It's not really a zapper, it's a it's
(21:39):
kind of not entirely accurate, but I like the idea
of using electricity to zap chocolate to make it better.
That's just an oversimplification of what happened, but that's okay.
I'll explain to you what was actually going on. They
built this thing where it starts with a bit of
a melting chamber. You can just think of it as
(21:59):
like a a pot. It could even be a glass vial. Really,
it could just be any little container that can hold chocolate.
They put the chocolate in the container, and they cover
the container, sealing it shut. They added compressed nitrogen gas
into the chamber simply really to just increase the pressure
(22:20):
inside the chamber itself. The chamber was heated so that
you had chocolate melting into a liquid. There was a
therma couple in there to make sure that the temperature
was correct so that the chocolate would not overheat or
cool down so much that it becomes solid again. And
then the base of this container was essentially a drain,
so there's like a hole at the bottom of the
(22:43):
container that liquid chocolate could flow through. Attached to that
was a tube, and inside the tube they put a
series of metal mesh screens, and the screens were what
generated the electric field. They had electricity running to those
screens and creating electric field that way in the direction
of the flow of chocolate, so the chocolate would end
(23:06):
up flowing very smoothly through the tube and didn't have
any issues. At the other end, they had another vessel
container that the liquid chocolate would flow into, it would
cool down solidify. So once that liquid chocolate flowed through
into the collecting vessel and once it was free of
(23:26):
the electric field, the cacal particles they went back to
their original shape immediately. Again, they didn't have to transform
or anything. It wasn't a gradual process. They boop moved
back into those globe shapes that they typically are in,
and the chocolate cooled and solidified and was, to all
(23:46):
intents and purposes, indistinguishable from the chocolate that was being
fed through at the top at that top chamber. So
they were able to reduce the viscosity of the flowing
chocolate and to the point where it was no there
were no issues of clogging, it was perfectly fine. So
(24:07):
they were able to prove that their hypothesis was correct,
that in fact, this electric field applied in this way
would decrease chocolate's viscosity. Hooray. But there's more to it
than that. So this experiment was not just a success.
The researchers actually realized that it had a lot more
implications than just having chocolate flow freely through a machine.
(24:32):
That again, the reason why chocolate has such a relatively
high fat content is to create that oily fluid to
reduce viscosity, to have the cacao particles suspended within it
at a density that's low enough so that you're not
likely to clog up the machines. But if you use
this approach, if you use the electric fields to reduce viscosity,
(24:57):
you don't need as much oil or fat in your
chocolate content. You could actually start with a recipe that
has less fat in it, and the electric fields would
take care of the viscosity problem, so you don't have
to have as much fat there. That also means you
could have more cacal in your mixture. It could be
(25:18):
a higher proportion of the overall recipe. So they found
that they could reduce the fat content in certain types
of chocolate by as much as twenty percent and still
have no negative impact on the fluid's viscosity. Now, it
depends on what type of chocolate they were using. They
were actually using name brand chocolates, you know, like chocolate bars.
(25:43):
They would try different types and depending on the type,
they could actually end up removing up to twenty percent
of the fat in the mixture and still have the
chocolate flow without any problems. And beyond that, the researchers
said that people who are tasting the chocolate afterward, because
keep in mind, other than the fact that there was
(26:05):
less fat in it, there was really no difference between
the original chocolate and the end result. They said that
the end result chocolate actually tasted better to them. He said,
I had a more intense cacw flavor. It was more
chocolatey than the original chocolate. Now that could be just subjective,
or it could be purely psychological, but it's not outside
(26:27):
the realm of possibility that by increasing the proportion of
chocolate of cacao in your mixture because you've removed some
of the fat, so you've got more cacal per unit
of chocolate than you would previously, that you would also
affect the taste. It is entirely possible that that is true.
(26:50):
It hasn't really been tested on a scientific level. It's
mostly people saying, hmm, this tastes really good. Also, I
should mention this is not the same as fat free chocolate.
Fat free chocolate is essentially using some different type of
fluid other than oil to suspend cacal particles. So fat
free chocolate has that particular weird taste. It's not the
(27:14):
same as the stuff that Temple University was producing. So
I just want to clear that up. It's not like
you would take a bite of a brand new chocolate
bar that was made using this procedure and think, oh,
this tastes like fat free chocolate. No, So the end
result here is that we could end up with better
(27:34):
tasting chocolate with less fat in it in the future,
which seems pretty awesome to me. Now, earlier I mentioned
that electroheological fluids are also called smart fluids. That's because
these fluids can change their viscosity almost instantly in the
presence of an electric or magnetic field, and then go
right back to what they were before once the field
(27:55):
is turned off, and they become really important in ways
be on making superior chocolate. For example, car manufacturers have
been using smart fluids and suspension and braking systems. The
fluid can actually go from relatively thin to thick in
just a moment's notice, which makes it superior to a
lot of mechanical solutions that would take time to propagate
(28:16):
through a system. And you can have a variable suspension
in this way. Imagine that you have a suspension, it's
a fluid suspension, like literally, it's a suspension for a
car with fluid in it, not that it was a
fluid that has a suspension in it. It's kind of confusing,
so car suspension's got fluid in it. Very high end
sports cars have these, and you can set your suspension
(28:37):
to different modes, like you can predetermine which mode you
want at any given time. So let's say you're going
to be driving on like a racetrack, a nice smooth racetrack,
and you're really going to push the car to its limits.
You might want a pretty stiff suspension for that to
really be able to feel the car as you're driving
(29:00):
along this very smooth surface. But that stiff suspension would
be a torture device. If you were driving down a
normal everyday road that had some bumps and maybe some
potholes in it, that would be very jarring. You would
feel every single little bump. So in that case, you'd
want a more loose suspension, a little spring in it.
(29:23):
So you might want to reduce the viscosity of the
fluid inside the suspension to allow for more give really,
and you could do that with a smart fluid and
just change the electric or magnetic field that ends up
affecting the viscosity of the fluid. So you can actually
have settings and say I want a very stiff suspension
(29:45):
in this circumstance and so it generates the electric field,
the viscosity increases and you get your stiff suspension, or
you might say, oh, I want it to be a
more forgiving suspension, and it turns off that electric field.
The viscosity decreases and you have your more your suspension
when more given it. It's a pretty cool idea. I
chatted with Scott Benjamin about this before I came in here.
(30:08):
He was very interested when I started talking about chocolate,
but then when I started talking about smart fluids, he
really lit up because he knew exactly what I was
talking about. I mean, Scott is a car genius and
knows everything there is to know about cars, it seems.
So we had a good discussion about, you know, the
physical properties of smart fluids and why they behave the
way they do. So this technology could be used in
(30:30):
lots of different applications moving forward. When you can induce
some mechanical change in a fluid with something as simple
as an electric or magnetic field, a lot of different
opportunities open up. But for me, you know, I'm happy
with the chocolate thing. I'm going to settle for that
because I do love me some chocolate that wraps up
the classic tech episode of How Tech Could Make Better Chocolate.
(30:53):
Hope you enjoyed it. If you have suggestions for topics,
I should cover future episodes of tech Stuff a couple
different ways you can let me know. One you can
go on over to Twitter and you can send me
a message. The show's handle is tech Stuff hsw or
if you prefer, you can download the iHeartRadio app. It's
free to download. It's free to use. Navigate on over
(31:15):
to tech Stuff by putting that into the little search
field that I'll take it to the tech Stuff podcast page.
You'll see a little microphone icon. If you click on that,
you can leave a voice message out, but thirty second
ten length either way. I hope you're doing well and
I'll talk to you again really soon. Tech Stuff is
(31:37):
an iHeartRadio production. For more podcasts from iHeartRadio, visit the
iHeartRadio app, Apple Podcasts, or wherever you listen to your
favorite shows.
TechStuff News
Hosts And Creators
Oz Woloshyn
Karah Preiss
Popular Podcasts
Stuff You Should Know
If you've ever wanted to know about champagne, satanism, the Stonewall Uprising, chaos theory, LSD, El Nino, true crime and Rosa Parks, then look no further. Josh and Chuck have you covered.
Crime Junkie
Does hearing about a true crime case always leave you scouring the internet for the truth behind the story? Dive into your next mystery with Crime Junkie. Every Monday, join your host Ashley Flowers as she unravels all the details of infamous and underreported true crime cases with her best friend Brit Prawat. From cold cases to missing persons and heroes in our community who seek justice, Crime Junkie is your destination for theories and stories you won’t hear anywhere else. Whether you're a seasoned true crime enthusiast or new to the genre, you'll find yourself on the edge of your seat awaiting a new episode every Monday. If you can never get enough true crime... Congratulations, you’ve found your people. Follow to join a community of Crime Junkies! Crime Junkie is presented by Audiochuck Media Company.
NFL Daily with Gregg Rosenthal
Gregg Rosenthal and a rotating crew of elite NFL Media co-hosts, including Patrick Claybon, Colleen Wolfe, Steve Wyche, Nick Shook and Jourdan Rodrigue of The Athletic get you caught up daily on all the NFL news and analysis you need to be smarter and funnier than your friends.