# Diamond Anvil Cell: Operation and Applications

https://www.youtube.com/watch?v=NkhiIRoSqag

[00:00] Imagine being able to recreate the extreme conditions found deep inside planets or even uh in the hearts of distant stars right here in a lab.
[00:09] It sounds like science fiction, right?
[00:11] Well, today we're taking a deep dive into a device that does just that.
[00:13] The diamond anvil cell or DAC.
[00:16] It really is a remarkable piece of engineering.
[00:19] It lets scientists explore the fundamental properties of matter under well mind-boggling pressures.
[00:25] mindboggling pressures that can reach over 770 gigapascals.
[00:30] That's uh 7.7 million atmospheres.
[00:34] Just to give you a sense, that's like the pressure right at the center of the Earth.
[00:37] Wow.
[00:37] Okay.
[00:39] So, our mission today is to unpack this uh ingenious design of the ESC, explore the really intricate process of setting up these delicate experiments, and they are delicate.
[00:47] Discover the cutting edge measurements they allow, and maybe reveal some of the surprising scientific breakthroughs they've made possible.
[00:54] We're drawing from practical guides, detailed manuals, scientific overviews, all that good stuff.
[00:58] Bringing you the key insights.
[00:59] Exactly.
[00:59] Okay, let's
[01:01] unpack this.
[01:01] So, at its heart, the DAX seems deceptively simple.
[01:05] Yeah.
[01:08] Just two opposing diamonds.
[01:08] But these aren't just any diamonds, like off-the-shelf ones, are they?
[01:11] Oh, not at all.
[01:11] No, we're talking high gem quality, essentially flawless diamonds, often around say 18 to 13 karat.
[01:18] Okay.
[01:18] And their tips, the clets, they're polished flat, typically maybe 100 to 250 micrometers across.
[01:25] They face each other.
[01:27] Oh.
[01:27] And they have to be perfectly parallel.
[01:31] Why is that so critical?
[01:31] Well, that precision is absolutely vital.
[01:33] It ensures the pressure is uniform across the sample, any slight tilt, even a tiny misalignment, and you concentrate the force, you get uneven pressure, and you can easily shatter a very expensive diamond.
[01:45] Right.
[01:45] Makes sense.
[01:45] And the force, how do you generate that kind of pressure?
[01:47] It comes from a force generating device.
[01:48] It could be as simple as tightening screws on the cell body or uh for more controlled pressure using hydraulic pressure like an oil filled bellows.
[01:58] What's just fascinating here is how such a compact device I mean you can
[02:01] often hold them in your hand.
[02:03] Some of them how they can generate pressures high enough to mimic environments deep inside planets.
[02:09] It lets scientists create materials, phases of matter that just don't exist under normal conditions here on the surface.
[02:15] Exactly. It's like a tiny window into alien environments.
[02:17] So you're basically creating miniature planetary cores in the lab in a sense.
[02:23] Yes. And the results are often things that challenge our basic understanding of chemistry and physics.
[02:27] We've seen uh for instance non-molecular ice X. Ice X.
[02:32] What's that?
[02:32] It's a phase of water ice that forms at very high pressures where the water molecules actually dissociate.
[02:38] It behaves completely differently from the ice, you know, and it could exist deep within ice giants or even Earth.
[02:45] That gives us clues about planetary interiors.
[02:46] Incredible. And other exotic materials.
[02:49] Oh yeah. Things like polymer nitrogen, a super dense form of nitrogen bonded together, not like the N2 gas we breathe.
[02:56] And even metallic phases of xenon.
[02:58] Xenon, a noble gas becoming metallic under enough pressure.
[03:01] Yes. The
[03:04] electron shells get squeezed so much they start to overlap, allowing conductivity.
[03:07] And beyond just making these things, a huge advantage of the DOC is that diamonds are transparent.
[03:14] Ah, so you can see what's happening precisely.
[03:16] You can shine visible light through X-rays, lasers.
[03:18] You can use all sorts of spectroscopic technique to directly observe the material's properties while it's under pressure.
[03:25] It gives scientists a real-time window into these extreme transformations.
[03:29] Okay, so let's get practical.
[03:31] How do you actually get a tiny sample in there and apply the pressure?
[03:35] It sounds uh like a real test of patience and steady hands.
[03:37] It certainly is.
[03:40] Yeah, patience is key.
[03:42] One really critical component is the gasket.
[03:44] The gasket.
[03:45] Okay.
[03:46] This is usually a thin metal disc.
[03:48] Often made of something strong but non-magnetic like reinium or maybe a tungsten alloy.
[03:50] First you pre-indent it.
[03:52] Pre-indent.
[03:53] You squeeze it between the two diamond tips to make it thinner in the center.
[03:56] Maybe down to 60 or 90 micrometers thick for say a 500 micrometer kellet diamond.
[04:01] Okay.
[04:02] So you thin it out right where the pressure
[04:05] will be highest.
[04:07] Exactly.
[04:07] Then you drill a tiny hole right in the center of that indented area.
[04:12] Typically about a third to a half the diameter of the diamond clet.
[04:14] How tiny are we talking?
[04:17] Well, if a klet is 250 micrometers, the hole might be uh 80 to 120 micrometers.
[04:23] Historically, people use tiny drills on watch makers lathes, but now there must be a better way.
[04:27] Oh yeah.
[04:27] Electrical discharge machining, EDM.
[04:32] It makes much cleaner, perfectly centered holes, much more reliable.
[04:35] Sometimes they might even sputter a thin layer of gold onto the gasket for certain electrical measurements.
[04:40] And inside that tiny, tiny hole in the gasket, that's where the sample goes.
[04:44] That's the sample chamber.
[04:46] Yes, the sample goes in there along with what we call the pressure transmitting medium.
[04:50] Okay.
[04:50] What does that do?
[04:52] That medium is absolutely vital.
[04:55] It surrounds the sample and transmits the pressure from the diamonds evenly onto the sample from all sides.
[04:59] You need what's called hydrostatic pressure.
[05:03] Hydrostatic meaning uniform pressure.
[05:03] Exactly.
[05:05] Uniform stress.
[05:08] If the diamond's pressed directly on a solid sample, the pressure wouldn't be even.
[05:10] The medium ensures it is, which is crucial for getting accurate results.
[05:15] What kind of mediums do you use?
[05:17] Well, for lower pressures, say up to a 10gpa, liquids can work.
[05:22] A common one is a 4:1 mixture of methanol and ethanol.
[05:27] But above that, liquids tend to solidify or become very viscous, losing that hydrostaticity.
[05:30] So for really high pressures, noble gases are preferred.
[05:34] Things like helium, neon, or argon.
[05:37] You load them cryogenically as liquids or gases and then seal the cell.
[05:42] They stay relatively soft and hydrostatic even after they solidify under pressure.
[05:46] Plus, they're transparent and don't interfere much with optical or x-ray measurements.
[05:51] Right.
[05:52] Because they're chemically inert.
[05:54] Precisely.
[05:54] Okay, here's where I imagine it gets really tricky.
[05:56] Getting those diamonds, the gasket, the sample, the medium all perfectly aligned.
[05:58] I hear it's incredibly finicky.
[06:01] You heard right.
[06:03] Precision is absolutely paramount.
[06:04] And yes, misalignment is
[06:06] probably the number one reason for breaking diamonds.
[06:07] Very costly mistake.
[06:10] So, how do you align them?
[06:11] Diamond alignment involves three main types.
[06:13] Translational side to side, rotational,
[06:16] making sure flats are aligned if they have them, and planer, ensuring the faces are perfectly parallel.
[06:19] And you do this how?
[06:21] Under a microscope?
[06:24] Yes.
[06:24] Typically under a high-powered microscope, you make tiny careful adjustments using set screws on the cell.
[06:30] Then once aligned, you often use special jigs to hold the diamonds perfectly still while you apply an epoxy.
[06:35] Glue.
[06:35] You glue the diamonds in essentially.
[06:39] Yes.
[06:39] A specialized epoxy like diecast mixed carefully is used to fix the diamond to its backing plate.
[06:46] Often made of tungsten carbide for support.
[06:47] The glue needs to be strong, but also ideally non-magnetic and stable.
[06:52] Even cleaning sounds like it needs care.
[06:54] Absolutely.
[06:54] You'd use ethanol or methanol, never acetone that can attack many epoxies.
[06:58] And the backing plates, the tungsten carbide supports, they also help prevent the diamond from cracking under the immense stress.
[07:06] The samples themselves must be microscopic.
[07:08] Yes, sub millimeter is standard.
[07:10] You might have a sample that's say 70 by 70 micrometers, maybe 20 micrometers thick inside a 200 micrometer diameter hole in the gasket.
[07:19] That small.
[07:19] And you have to be careful not to make the sample too big for the chamber.
[07:24] If it touches the gasket walls or gets squeezed directly by the diamonds, you lose hydrostaticity and your results can be way off.
[07:28] And you mentioned ruby earlier, right?
[07:30] Often tiny ruby chips just a few micrometers across are placed in the sample chamber alongside the actual sample as pressure gauges.
[07:40] Exactly.
[07:40] Ruby fluorescence.
[07:43] The light it emits when you shine a laser on it shifts wavelength a very well-calibrated way with pressure.
[07:50] So you measure that shift and you know the pressure inside the cell.
[07:52] I also saw a mention of wiring things up inside the cell for conductivity tests.
[07:56] That looks like a whole different level of complexity almost an art form.
[08:00] It really is.
[08:00] Yeah.
[08:00] Connecting ultrafine wires, maybe just tens of micrometers thick,
[08:07] from the sample inside to external measurement leads.
[08:11] It requires incredibly careful application of epoxy for insulation and mechanical stability.
[08:15] Maybe using conductive silver paint for contacts.
[08:17] And for things like magnetic measurements, AC susceptibility, right?
[08:22] For AC susceptibility, you need tiny coils inside.
[08:24] You actually wind miniature coils, sometimes just 60 micrometer copper wire, maybe multiple layers, and carefully glue them into recesses in the gasket or near the diamonds.
[08:34] Wow.
[08:34] And soldering is bad.
[08:36] Solder often contains lead or tin, which can become superconducting or have magnetic signals, especially at low temperatures.
[08:43] So, spark welding is preferred.
[08:45] You use very specific settings like maybe 80 volts and a short pulse to weld say copper or gold wires together without introducing unwanted magnetic materials.
[08:54] It's delicate work.
[08:57] Sounds incredibly fiddly.
[08:57] It is.
[08:59] You might even have to rotate the sample stage slightly after welding just to detach the tungsten electrode from the wire without breaking anything.
[09:04] Okay.
[09:04] So, let's say you've managed this
[09:08] incredible feat of delicate assembly.
[09:10] It's all sealed up.
[09:12] How do you actually measure what's happening inside at these extreme pressures and maybe temperatures too, right?
[09:16] Measurements.
[09:18] So pressure, as we said, is primarily done using ruby fluorescents.
[09:20] You shine a laser on those little ruby chips inside, collect the fluorescent light with a spectrometer.
[09:27] Okay.
[09:27] And measure the wavelength of the main peaks, the R1 and R2 lines.
[09:29] You use a neon lamp spectrum for precise wavelength calibration.
[09:35] Then you plug that wavelength shift into established equations like the chioke expression which is pretty accurate up to about 150 gpa.
[09:40] And above that does ruby stop working?
[09:42] It gets more difficult.
[09:44] The fluoresence gets weaker and broader.
[09:48] So at really high pressures, often above 100 gpa or so, scientists increasingly rely on ROM measurements of the diamond anvils themselves.
[09:55] Measuring the diamonds, how does that tell you the pressure?
[09:58] The frequency of a specific vibration in the diamond crystal lattice, the diamond vibrant also shifts predictably with pressure.
[10:03] By measuring that ROM shift right at the tip of the diamond, very close to the sample, you can get an
[10:09] accurate pressure reading.
[10:10] Okay, pressure covered.
[10:12] What else can you probe inside the DSSE?
[10:14] You mentioned AC susceptibility.
[10:18] Yes, AC susceptibility.
[10:20] This measures how a material's magnetization responds to a small oscillating magnetic field.
[10:25] It's great for detecting magnetic phase transitions like a material becoming ferroagnetic or superconducting.
[10:31] You use those tiny coils we talked about connected to sensitive lockin amplifiers outside.
[10:35] But interference must be a huge issue.
[10:37] Oh, absolutely.
[10:39] It's critical that everything near the sample, the gasket, the backing plates, the epoxy, even tiny impurities in them is non-magnetic.
[10:45] Even a minuscule ferroagnetic impurity, maybe in the gasket material like reinium or tungsten carbide, can create a background signal, especially one that changes with temperature, potentially masking the real signal from your tiny sample.
[10:58] You have to carefully test all your components beforehand, right?
[11:02] And electrical properties like resistivity.
[11:04] For resistivity measurements, you need to electrically isolate the sample and bring wires to it.
[11:07] This often involves
[11:09] creating an insulated gasket.
[11:12] Insulated how?
[11:13] You might take your pre-indented metal gasket and press a mixture of diamond powder and epoxy into the indentation.
[11:19] Diamond powder is insulating.
[11:22] Once that cures, you have an insulating layer on the metal gasket.
[11:25] Then you carefully place tiny electrodes, often cut from thin platinum foil, maybe gold or palladium, onto this insulating layer.
[11:34] They wire them up.
[11:36] Exactly.
[11:38] You position them so they contact the sample, but not the underlying metal gasket outside the sample chamber.
[11:42] that would cause a short circuit.
[11:45] It's very precise work, often involving little tricks like using a tiny dab of superlue to hold masking tape in place while you position things.
[11:51] It sounds like you need the skills of a watch maker and an electrical engineer combined.
[11:55] Pretty much.
[11:57] And then there's temperature, right?
[11:59] Recreating planetary cores means extreme heat, but you also mentioned cooling.
[12:03] Exactly.
[12:05] Temperature control in DAX is incredibly versatile.
[12:07] For heating, you can use external resistive heaters wrapped around the cell body or the anvils.
[12:08] In an inert
[12:11] atmosphere to prevent oxidation, you can reach over a,000° C, maybe even up to,400° C with some designs.
[12:18] And for even higher temperatures, laser heating, you shine high power lasers, often infrared lasers like WG lasers, directly through the diamonds onto the sample.
[12:28] The sample absorbs the laser light and heats up dramatically.
[12:31] How hot can that get?
[12:32] Potentially up to 7,000 Kelvin.
[12:35] hotter than the surface of the sun.
[12:37] Though measuring temperature accurately with laser heating is tricky, especially below about 12,200° C, where the sample doesn't glow brightly enough for standard optical parametry.
[12:46] And you need to heat evenly.
[12:48] Yes, that's crucial.
[12:48] So, typically double-sided laser heating is used with lasers coming in from both sides, hitting the same spot on the sample to minimize temperature gradients.
[12:57] Okay.
[12:57] And cooling.
[12:57] You can go really cold, too.
[13:00] Definitely you can place the entire DAC inside cryostats by using liquid helium itself as the pressure medium loading it into the cell and using sophisticated dilution
[13:11] refrigerators you can cool the sample down to millichelvin temperatures.
[13:13] Wow.
[13:15] So for millichel up to 7,000 Kelvin and millions of atmospheres.
[13:18] That's an incredible range.
[13:20] It really is.
[13:23] But given how complex and delicate all this is, you mentioned finicky.
[13:25] What are some of the common pitfalls?
[13:28] What goes wrong?
[13:31] Ah, where to start?
[13:33] High-pressure experiments are, yes, famously finicky.
[13:36] One of the biggest headaches is just figuring out if the signal you're measuring is actually coming from your sample as opposed to as opposed to the gasket material changing under pressure or the pressure medium itself undergoing a transition or electrical noise or even sometimes cosmic rays hitting your detector.
[13:53] Data analysis can be really challenging.
[13:55] You need careful background measurements, subtractions, lots of cross checks.
[13:56] So, it's not always straightforward.
[13:59] Far from it.
[14:00] Often, it feels like you're relying on well, cobble together hacks, little tricks and techniques developed over years to make things work or simplify analysis.
[14:07] And you absolutely need patience.
[14:09] I've seen guides that literally end a complex
[14:13] setup procedure with the instruction.
[14:15] Celebrate and hope.
[14:19] Laugh slightly.
[14:19] Right.
[14:22] That captures the feeling.
[14:22] I imagine it really does.
[14:24] Yeah.
[14:24] Because you can spend days preparing an experiment, getting everything perfect, and then something unexpected happens, right?
[14:30] A tiny leak, a broken wire you can't see, an air bubble trapped in the medium.
[14:34] It requires perseverance.
[14:34] Okay, so beyond the fundamental physics and making these exotic materials, what are some of the more surprising applications?
[14:42] Where else is this data technology making an impact?
[14:46] Well, beyond the material science relevant to say planetary interiors or designing super hard materials, the day has found some really innovative uses.
[14:53] One area that's quite fascinating is astrobiology.
[14:57] How does high pressure relate to the search for life?
[15:02] Well, it allows us to test the limits of life.
[15:07] Can life survive or even thrive under the immense pressures found deep within Earth or potentially on other planets or moons, places we previously might have written off as
[15:14] uninhabitable?
[15:15] Okay, now this sounds really interesting.
[15:17] Using these pressure cells to understand the boundaries of life itself.
[15:22] Exactly. Scientists have actually put living organisms into DAX to see what happens.
[15:24] For example, back in 2002, there was a landmark study.
[15:29] They took common bacteria as E.oli and another type called Shouanellan densis.
[15:34] Okay.
[15:37] Put them in a nutrient broth inside a DIA and cranked up the pressure to 1.6 GPA.
[15:39] 1.6 6 gigap pascals, over 16,000 times the atmospheric pressure here at sea level.
[15:46] Immense pressure.
[15:48] And what happened to the bacteria?
[15:50] Well, they left them there for 30 hours and afterwards about 1% of them had survived.
[15:54] 1% survived 16,000 atmospheres.
[15:57] That's incredible.
[15:59] It is.
[15:59] And what's even more remarkable is that under that pressure, the water solution they were in actually turned into a solid form of ice called ice and high, even though it was at room temperature.
[16:07] All right, temperature ice.
[16:07] Yes.
[16:09] one of the many exotic phases of ice that form under pressure.
[16:11] Yet, even encased in this ice, the surviving bacteria were
[16:15] found to still be metabolically active.
[16:17] They could break down a nutrient formate that was provided in the broth.
[16:21] So, they were alive and functioning.
[16:22] It appears so.
[16:24] They even formed little liquid pockets around themselves as a result of their metabolic activity and microscopy showed them clinging to the diamond surfaces almost like they were trying to move.
[16:31] Wow.
[16:31] Any other examples?
[16:34] Yeah, other studies have shown that even baker's yeast, sacchroyces cervisier, can actually grow and reproduce at pressures around 15 to 50 MPa, which is still hundreds of times atmospheric pressure.
[16:44] So when these results first came out, the bacteria surviving 1.6 gpa, what was the reaction in the scientific community?
[16:52] Was it immediately accepted?
[16:54] There was definitely a lot of excitement, maybe a bit of initial skepticism.
[16:59] You know, was it really metabolic activity or just some residual chemical reaction?
[17:03] But subsequent work using various techniques has broadly confirmed that microbial life can indeed survive and maintain some metabolic function at these truly extreme pressures.
[17:11] And what did that discovery do to our thinking about where life could exist?
[17:15] It fundamentally challenged
[17:17] our definition of a habitable environment.
[17:19] Before the focus was very much on Goldilock zones, moderate temperatures, liquid water on the surface.
[17:25] These Deianne experiments show that life might persist deep underground or in the oceans of icy moons like Europa or Enceladus where pressures are enormous but liquid water might exist beneath the ice.
[17:37] It forced us to think much more broadly.
[17:39] So it dramatically expanded the potential real estate for life in the universe.
[17:43] Absolutely.
[17:45] If life can handle pressure regimes that turn water into solid ice at room temperature, it suggests that the physical limits for life are far wider than we previously imagined.
[17:53] It pushes our understanding of what life can endure and where we might find it both here on Earth in deep unexplored niches and potentially far beyond.
[18:01] So from recreating those colossal pressures inside planets to probing the very edge of life's resilience, the diamond anvil cell really is an amazing testament to human ingenuity, isn't it?
[18:12] And our well endless curiosity.
[18:15] It truly is.
[18:18] tool that lets us peek into these hidden worlds, whether they're deep beneath our feet or across the vastness of the cosmos.
[18:25] It teaches us that under these extreme conditions, the familiar rules of chemistry and physics can bend or even break.
[18:32] Surprising things happen.
[18:32] Exactly.
[18:34] Phenomena emerge that challenge our basic assumptions about how materials behave and as we've seen about what life itself is capable of.
[18:41] It really underscores that the universe is likely far more diverse and life potentially far more adaptable than our intuition might suggest.
[18:50] Which brings us to a final thought for you, our listener.
[18:54] Given these extraordinary conditions we can now create in the lab, conditions mimicking deep planets or maybe even asteroid impacts, and given the surprising resilience of life we've seen inside the DC, what does this really imply for our search for life beyond Earth and perhaps even for finding life in unexpected places right here on our own planet?
[19:12] How should this ability to study life under extreme pressure reshape our understanding of what makes an environment habitable?
[19:18] Where else might life be hiding?