Who doesn’t love a bubble?

Technically, a bubble is any gas  surrounded by a solid or a liquid. It could be a lot of liquid, like the ones made   when you open that bottle of water  you didn’t realize was carbonated… or, it could be the thinnest possible  film of liquid, surrounded by more air.

Like these! But bubbles do more than tickle our  tongues, and delight our inner child. They’re cheap, easy to handle, and versatile,   which makes them a great candidate  for scientific experimentation, too.

Over the years, these whimsical wonders  have found their way into a ton of research,   from human health to sci-fi sensors. So let’s take a look at some of the  surprisingly sciencey uses for bubbles. [♪ INTRO] Our first example comes to us  courtesy of particle physics. Back in the first half of the 20th century,   scientists used this nifty  tech called cloud chambers.

As the name suggests, they  were filled with a vapor. And as an energetic particle passed though,   it would cause some of that vapor  to condense into tiny droplets. Then in 1952, the American  physicist Donald Glaser took   a look at a cloud chamber and thought to himself: “What if we swapped everything around?” In  other words, he invented the bubble chamber.

Instead of a vapor, you start with a  liquid inside a pressure-tight container. You then heat it to just below its boiling point. After you’ve got that set up, a piston  built into the chamber pulls out,   reducing the pressure inside the container.

Since liquids tend to have lower  boiling points at lower pressures,   the liquid suddenly finds  itself above its boiling point. It’s still a liquid, although scientists call   it superheated so you know  something weird is going on. Whenever a charged particle passes through  the chamber, it’ll interact with a trail of   molecules in this superheated liquid and  leave them with a charge of their own.

These newly charged particles can then trigger  the liquid around them to turn into a gas. And voila, you’ve got yourself a bunch of bubbles! Scientists can measure these bubbly  tracks, like how long and curvy they are,   to calculate the properties of that original  interloping particle, including its energy,   mass, and ultimately exactly what kind  of particle it was in the first place.

Bubble chambers quickly became a more effective  tool than their cloud chamber predecessors,   on account of the liquid inside them  having a much higher density than a vapour. There were way more molecules for a  mystery particle to interact with,   so physicists could study  particles with even higher   energies that wouldn’t be slowed  down enough inside a cloud chamber. For his invention, Glaser was awarded  the Nobel prize in Physics in 1960.

And during the 70 and 80s, a 1000-ton  bubble chamber at CERN helped reveal   some of the crucial details of the  Standard Model of Particle Physics. The instrument was called Gargamelle,   and it not only unlocked crucial information  about the existence and properties of quarks. It helped scientists discover the W and Z bosons,   which are basically the particles that mediate  the entire process of radioactive decay.

Today, bubble chambers are still being used to  search for heavyweight particles called WIMPs,   which some scientists think could be behind   the mysterious dark matter  that permeates the universe. However, in other areas of particle physics,   bubble chambers have largely been replaced  by more high-tech, electronic instruments. Not because those scientists secretly hate  bubbles, but because the analog technology   can’t keep up with the high energies of  the particles we have left to investigate.

But that doesn’t mean there aren’t other   scientific fields where bubbles are  able to keep pace with electronics. Like computing! Modern computers are typically  made from electronic components,   and work by shuttling around  bits of high and low voltage.

However, there are certain cases where it helps  to have computers that are a bit more… fluid. In the field of microfluidics,   scientists move teeny tiny volumes of fluid  through channels to do chemical reactions. We’re talking picoliters here, which  are a billionth of a milliliter.

The tech basically replaces all the flasks, tubes,   and glassware you associate with a stereotypical  chemistry lab, and it’s useful when you’re dealing   with incredibly expensive chemicals or want  to try a bunch of different combinations. If you’re wondering what the heck this has  to do with computers, we’re getting to that. Traditionally, these microfluidic  devices are controlled by tiny   valves inside their channels that are  programmed and controlled externally.

But in 2007, scientists found a way to  use bubbles within the channels to not   only do the chemical reactions,  but control the flow internally. No external oversight needed! The team carefully designed the layout of the  channels on their microfluidic device to act   like logic gates, which produce a certain output  depending on the exact combination of inputs.

But instead of the classic voltage variation you   find in traditional computing, these  inputs come in the form of bubbles. See, when a bubble reaches a junction in a  network of narrow channels…a fork in the road,   so to speak… it will always follow  the path of least resistance. Like, say, the slightly wider of the two channels.

But if a second bubble reaches that same  junction, and finds the wider channel   blocked by the first bubble, it will have  no choice but to go in the other direction. In other words, the team basically used channel  thicknesses to create an AND-OR logic gate. But with more complex networks of channels,  they also designed a full logic family for these   tiny bubble computers, including gates,  memories, amplifiers, and oscillators.

While this approach is about 1000  times slower than electronic circuits,   it’s still 100 times faster than the  traditional valve-based microfluidic control. Another cool thing is, although the researchers  proved the concept using nitrogen bubbles in   water, bubble circuits could work with  any two fluid phases that don’t mix. This means that they could be used  for so-called ‘lab on a chip’ devices,   which are used in the quest to  develop new drugs, for example.

Other possible applications for the bubble  computers include programmable print heads,   devices for cheap but large-scale chemical  analysis, and bespoke chemical dispensaries. All places where it helps to combine  chemistry and computing into one device. We’ll just have to see  where the research takes us.

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Thanks! We now move from bubbles getting  moved around inside a thing,   to bubbles moving a thing inside them. Because it turns out that an ordinary  soap bubble can make a pretty good laser.

And it’s all thanks to a quirky bit of  physics inspired by a cathedral in London. Lasers work by amplifying light rays and  collecting them into a coherent beam. In fact, that’s what the A in  Laser stands for: amplification.

Usually, this amplification is done  by bouncing the light between mirrors. But you can also do it by bouncing it around  the inside of a curved surface, like a sphere. Doing this creates what’s known  as whispering gallery modes,   named after a strange acoustic phenomenon  that occurs inside St Paul’s Cathedral.

If you and a friend are standing on opposite  ends of the 32-meter-wide dome, and one of you   whispers, the other can hear you just as clear  as if you were standing right next to each other. I mean, it doesn’t have to be your friend. It could also be an enemy, a complete stranger,  parasocial crushes…the possibilities are endless!

The reason why this happens is because of the way  the sound waves reflect off the curving surface. The same thing happens with  light waves inside a curve, too. And all these bouncing waves wind up  interfering with each other in such a   way that they get amplified… just like in a laser.

Now, lasers have been made from spheres  and cylinders made of glass for decades. But in 2024, scientists showed that  a soap bubble could also do the job. The trick is to add a special fluorescent dye to   the water that gets trapped in  the soapy part of your bubble.

That way, when you shine a particular  wavelength of light at the bubble,   it stimulates the dye molecules and  triggers the release of more light. Every so often, a new light ray just  so happens to be emitted into one of   the bubble’s whispering gallery modes,  which stimulates even more dye emission. In other words, amplified light.

You’ve got yourself a laser. Now, these soap bubble lasers  are a bit unpredictable,   because as thin as they might look, bubble  “surfaces” actually have a thickness to them. The light will end up bouncing off both  the inner and outer sides of that surface.

Not only that, but the thickness at  any given spot is always changing,   as gravity pulls the water  to the bottom of the bubble. So while you can make a laser, its  frequency isn’t particularly consistent. Instead of monochromatic light, you  get a broad and changeable spectrum,   which is hard to interpret and difficult  to use for any real-world applications.

And eventually it also pops. To solve all of these problems, the  researchers suggested swapping soap   and water for something called  a smectic liquid crystal. You know how some computer monitors and watches   have LCD screens that go all  rainbowy when you press on them?

Yeah, those bubbles are made of the same stuff. Importantly, with liquid crystals, the  bubbles don’t have any water involved. This makes them more controllable  with a consistent layer thickness.

It also makes them less prone to  bursting, lasting up to 10 minutes. But what, you may ask, is the point of  making LCD bubble lasers in the first place? The difference between using these and  solid glass spheres to make a laser is   that a bubble is soft and filled with air, and  so it’s sensitive to environmental conditions.

The exact types of light that get  amplified ultimately depend on the size,   shape, and air pressure of the bubble. And those properties are, in turn,   affected by such things as the  ambient temperature and pressure. In other words, a bubble laser could be used  to monitor pressure changes in an environment.

And with surprisingly high accuracy, too. I’m talking changes as small as 1.5 Pascals! That’s about 100,000th the  air pressure at sea level.

And at the same time, it’d be  robust enough to withstand up   to 100 atmospheres of pressure without popping. All of this research is pretty new,   so the bubbles haven’t yet been  put to the test in the real world. But the team behind the technology thinks their   approach could be useful  in the aerospace industry.

And on top of that, what works for  light could also work for sound. Those whispering gallery modes  could come full circle to help   scientists create bubble laser microphones. But speaking of sound waves… Bubbles have also found a critical  role in the field of medical imaging.

Specifically, in improving ultrasound scans. Traditional medical imaging often  involves adding something into the   body to increase the visibility,  or more accurately the contrast,   of whatever structure your  device is trying to look at. For example, if you’re getting  an MRI scan of your brain,   you can be injected with a contrast agent  containing the heavy metal gadolinium.

Or you might be given a barium  meal before an X-ray or CT scan,   to increase the visibility of your gut. They gave that to my cat the time that he ate   foam and had to get an x-ray  to get it out of his tummy. But for an ultrasound, it’s  a little bit different.

Ultrasound imagery relies on sound  waves bouncing off an interface   between two different substances in the body. It’s often used to look at very  squishy things, like the liver,   the heart, and perhaps most  famously, growing babies. But sometimes, it’s hard for our  technology to distinguish between   all the different squishy things in the body.

It can be especially hard to  image blood flow with ultrasound,   since the lower density liquid appears  dark compared to the surrounding tissue,   which means you don’t have a  lot of information to work with. And since blood flow is crucial to telling us   how well our organs are working,  this can be a bit of a problem. Luckily, scientists realized you can increase  the contrast by introducing a different state   of matter to the bloodstream,  in the form of tiny gas bubbles.

Now normally, gas bubbles are the  last thing you want inside your body. But in the case of microbubble contrast, which  requires less than 2 milliliters of gas in total,   the volumes are so small that  they don’t pose a major risk. Each of these microbubbles  contains an insoluble gas,   and is designed to be about the  same size as red blood cells.

That way, they can go wherever the blood goes. And with about a billion bubbles per  millilitre, a little goes a long way. They’re also just the right size for the  ultrasound waves passing over them to make   them expand and contract in resonance…that’s  the phenomenon you experience when you’re on   a swing pumping your legs back and forth at  just the right rate to make you go higher.

This rapid vibration winds up making the  microbubbles super reflective compared to   the stuff around them, and therefore making the  blood vessels they’re inside of more visible. Some parts of the body can benefit  from this effect more than others:   For example, bubbles can improve the  visibility of blood flow to the brain,   which is usually difficult to see on account  of that big ol’ bony skull getting in the way. Meanwhile, in the liver, doctors can more easily  spot lesions caused by things like liver cancer.

These can show up on normal ultrasounds,  but microbubble contrast reveals lesions   when they’re much smaller,  leading to earlier diagnosis. And in the heart, the fact that the bubbles  are in the blood but not in the heart tissue   allows cardiologists to clearly see the  difference between them, helping to measure   things like the volume of the chambers, and  the condition of the heart walls and valves. But that’s not all!

By using more intense sound waves to  pop the bubbles in a specific area,   doctors can time how long it takes for  that region to refill with bubbles,   giving a read on how fast the blood flow is. Microbubble contrast has become a staple  of ultrasound imagery, but it’s also being   investigated as a way of treating a patient too,  as a kind of targeted drug delivery mechanism. This is because the presence of  the bubbles makes it easier to   penetrate cell membranes without damaging them.

So hypothetically, you can put your drug inside  some bubbles, inject them into a patient’s blood,   and then focus an ultrasound beam onto the  place you want that drug to be delivered. When the high-intensity ultrasound waves pop the   bubbles, the drug pushes into the  cells directly where it’s needed. This therapy is still in the early phases  of research, but the people working on it   propose it could be especially helpful  for breaching the blood-brain barrier,   which is usually very effective at keeping foreign   substances in the blood away from  the delicate cells of the… the brain.

So hypothetically, bubbles could help  us treat things like brain tumors and   Alzheimer’s without resorting to surgery. These seemingly sci-fi bubble therapies  might be just around the corner. But they’re not the only super futuristic  bubble application being explored.

Scientists have recently figured out how to use   bubbles to encode and store  messages in blocks of ice! Whether it’s in your freezer  or beneath a penguin’s feet,   water ice naturally forms  with bubbles trapped inside. And those bubbles can either  be egg-shaped or needle-shaped.

Originally, the team behind this  research was just trying to figure   out what conditions caused those egg-  or needle-shaped bubbles to form,   as well as what conditions would  create ice with no bubbles at all. It turns out, a bubble’s shape depends on the  rate of freezing: the fastest freezing creates   egg-shaped bubbles; if it’s a little slower, the  freezing makes a mixture of eggs and needles. If it’s even slower than  that, you just get needles.

And finally, the slowest freezing rate… less than   3 micrometers per second…gives  you clear ice with no bubbles. So if you’re a fan of whisky on the rocks,  there’s a free tip for your crystal clear ice! By manually controlling the freezing rate of  a thin vertical slice of ice…by tweaking the   temperature of a cold plate at its  base…the team discovered that they   could create whatever shape bubbles  they wanted, in whatever order.

This allowed them to then try encoding information  using morse code and binary code, assigning layers   of clear ice and bubbly ice to either ‘dits’  and ‘dahs’, or to 0s and 1s, respectively. Binary proved to be more useful, since it allowed  messages up to 10 times longer to be recorded. In addition, the team found their encoded  messages were relatively easy to read.

A greyscale image of the surface of the ice  shows dark regions where there were no bubbles,   and lighter regions of different shades  for the egg and needle bubble layers. With this information, a computer can  quickly decode the frozen message. Now at first glance, it might  be hard to see a practical use   for this frozen-bubble data storage system.

But their paper notes that encoding  information this way uses less energy   than electronic telecoms, and it can  be preserved for a really long time. In Antarctica, scientists have recovered ice cores   full of natural bubbles that are  more than one million years old! For obvious reasons, this particular technology is   going to be most valuable  in naturally cold places.

But that can also include places that  aren’t even on Earth, like Mars or Europa! So who knows? Maybe thousands of years from now, after humanity  has accidentally wiped most of itself off of the   face of the universe, some alien archaeologist  will dig up what they think is a super important   message we’ve left behind and it’s, like,  “Ea-Nasir sells terrible bubble mixture”.

Maybe bubbles will be the messaging medium  of a dystopian future, or maybe they’ll   help elevate us to an advanced civilization  based on bubble computers and bubble lasers. But for now, they might just be  the low-tech, high-potential,   overlooked heroes of the scientific world. [♪ OUTRO]