This episode is brought to you by Brilliant. Humanity has many ambitions to reach upward to the stars, but those ambitions are only as strong as the materials those foundations are built on. So today, we’ll be looking at what advances in materials we may see in the next generation or century, though, we will also leap distantly into the future near the end to discuss the near-magic materials we hope future science might give us a path to, materials so strong they make steel seem like warm butter. Now we often do deep dives on certain topics here on Science & Futurism with Isaac Arthur, like we did with our focused look at Graphene last year, or Metamaterials a few years back. However, today’s topic is a bit broader, and so we will be touching on many different topics and many different applications.
We’ll be looking at objects that emit smells or light when exposed to air, advances in aerogels, smart materials, self-repairing ones, programmable matter, zero-g materials, new uses for liquid crystals, two-dimensional materials like graphene, but less-known, plus many more. Some of them, like Graphene, probably do deserve their own episodes, and so we’ll follow this episode with a poll over on the Channel’s Community page to pick one of these topics, so it will get its own dedicated episode in a few months. In the meantime, though, we’ve got a lot to cover in a single episode, so grab a drink and a snack. There is a tendency to think of super-materials in terms of those which are super-strong, that you can hang a building from a string of, or which could survive a tank battalion firing volleys of shells into it. Things you could make Captain America’s Shield or Wolverine’s Claws out of. And yet there are a lot of other equally valuable traits a material might have, and I thought we’d start by cataloging a few of those, and what the current reigning champion is, very quickly.
For strongest or toughest materials, those can vary whether we’re talking about how much weight it can hold, versus how much can press down on it, tensile strength versus compressive strength, and indeed even that can vary on the situation a lot, since one metal might be much weaker at a change in temperature or pressure. Bulk Modulus, the ability of a material to resist being compressed, as opposed to strained or sheared, is generally thought to be all about the electrons around that atom, and results in a graph that oscillates up and down and back up again as you move through the periodic table. Major peaks occur at Carbon – particularly its allotrope diamond – and Ruthenium and Osmium, with some lesser peaks including Silicon and Uranium. Osmium’s is the highest but this is a very rare substance, also the densest known element and it’s dual champion status as strongest and densest is not coincidental. We do not expect any alloy would be stronger in terms of Bulk Modulus, so Osmium will probably keep that champion status unless some transuranic element can be found that is stronger and has a half-life long enough to be worth building out of. This is one interest in the often discussed Island of Stability, a hypothetical region of the periodic table usually thought to be around 140 where materials would have long half-lives, or so some believe, we haven’t made any yet.
Of course, even those transuranic elements we have discovered are so small in quantity – since we have to make them an atom at a time – that their properties are poorly known. We can now begin to test things like compressive strength of just a handful of atoms with lasers, and that also raises an interesting use of lasers for creating unique materials we’ll discuss later. Also while alloys might not be stronger in this regard, allotropes of a given substance would vary in strength, like Graphene and Diamond both do as allotropes of carbon. So we may find some unknown allotropes of materials that do better than regular Osmium does, but we would not expect a big jump, if any. For strongest tensile strength, this title also remains with a long running champ, Graphene, though it is but one of many quasi-two-dimensional materials, many with interesting properties and some better than graphene in one role or another, and we’ll discuss those more today too.
Incidentally while the densest material is Osmium, the least dense solid is Aerographene, a type of Aerogel made of graphene, it is less dense than actual air. Aerogels are surprisingly strong materials that are feather light, and whose main use is as a thermal insulator as they can hold a lot of weight and pressure but barely transmit heat. This means they can potentially replace vacuum flasks, though their main uses are insulation for specialized markets, like pipeline insulation, paint thickeners, battery heat insulators, and so on. Right now it costs around 50,000 dollars a kilogram - though this is only a dollar a cubic centimeter given how light it is, hence why it's economically viable for keeping your laptop battery from heating up your laptop.
As costs drop, as they probably will, expect to see it in many more residential applications, potentially including your coffee mug and cookware. Additionally Aerographene has shown itself to work very well for 3D printing, which opens all sorts of new doors. Aerogel’s lightness makes it unsurpassed as a sturdy light-weight heat insulating material, but in terms of how hot it can go, we have a new champion. Tungsten was the long running leader for highest melting temperature of any metal, at nearly 6200 Fahrenheit or 3400 Celsius, though it usually gets mixed with Rhenium – whose melting point isn’t much lower – to create an alloy with a higher strength and corrosion resistance when used as a refractory material, and it's often alloyed with nickel, iron, copper, or even thorium to produce high-temperature sturdy materials with other necessary properties like electric conductivity. However the new champion for highest melting point of a metal is an alloy of hafnium, with Tantalum and carbon, at 7460 Fahrenheit or 4126 Celsius, vastly higher than Tungsten.
We’ve also had good results with Hafnium alloyed with Nickel and Carbon. I should probably note that carbon actually has a slightly higher melting point than Tungsten does as an element but not as a metal, and still far short of this Hafnium-Tantalum-Carbon alloy. On the low end, the element with the lowest melting point is still Helium, at just about absolute zero, 4.2 Kelvin, or -458 Fahrenheit or -272 Celsius. You mostly won’t find helium in its solid form outside a lab as even the Cosmic Microwave background radiation that permeates all the Universe is at 2.7 Kelvin and the coldest known place in the Universe is the Boomerang Nebula, about 5000 light years away, and it is at 4 Kelvin. The hottest place in the Universe is quite debatable - but barring the Big Bang, the invisible hearts of black holes, supernovae, or laboratory supercolliders - it would go to neutron stars, and with those aforementioned exceptions they’d also be the densest things in the Universe, far beyond Osmium, and is where the term Neutronium comes from, a popular superstrong material in science fiction.
It probably wouldn’t be strong in reality as degenerate neutron matter is not so much ‘strong’ as gravity is, binding all that matter together at crushing pressure, the neutrons are all that’s strong enough to resist being crushed by gravity at that strength. Ironically gravity is the weakest force, and one portion of one of those other forces, the magnetic fields of the electromagnetic force, is very hard to shield materials against. Any ferromagnetic material can help shield against magnetic fields but not very well, and for a long time the leader in this regard was mu-metal, which is a bit of blanket term for various nickel-iron ferromagnetic alloys with a high permeability, the symbol for which is mu, the Greek Letter that looks like a lower-case u and where the name mu metal derives from. However some year back experiments with metamaterials started showing us options like dielectric singularities and magnetic wormholes and while mu metal remains the reigning champion, it seems almost certain that title will next be given to some sort of metamaterial, it’s just a question of when. I should note that any sort of material that can block or dampen any of the forces is very handy.
As an example, while current physics doesn’t really allow for a gravity-blocking paint of material such as we see in some early scifi like Cavorite in H.G. Wells’s The First Men in the Moon, something able to block, reflect, or focus gravity waves or gravitons would be of incredible value, and same for anything able to interact strongly with neutrinos or dark matter. See our Dark Matter Technologies episode for some more discussions of those sorts of far-future options. Things which can reflect, absorb, or transmit other particles or forces are always of interest to us in material science, whether we’re talking about something photons can pass through but is sturdy, as clear as glass but tougher than steel, or something which moves smoothly through other things, like a friction-less material better than Teflon, or superior to oils in viscosity. For clear options, the Transparent Aluminum famous from Star Trek has in many ways long since been bested, but it's hard to call a winner because some options are strong and clear but not super clear, others handle shock well, making them good for collision resistance but not good for ultraviolet wear and tear, and so on. Diamond probably remains the all around favorite if we can upscale production – making diamond is quite easy in many ways but it's still not something we can do in bulk to start making windows.
Polycarbonate remains the cheap and tough champ, while clay nanosheets mimicking the brick-and-mortar molecular structure of seashells continue to gain ground in that and many other applications. We do actually have literal Transparent Aluminum – Aluminum Oxynitride or ALON is a transparent ceramic made of Aluminum, Oxygen, and Nitrogen, and it is quite sturdy compared to glass, coming in around the hardness of sapphire and spinel. It’s also already commercially available for windows and domes, well ahead of its use in the 23rd century of Star Trek, much like the flip phone communicator. Communicators and Computers advanced far more rapidly than Star Trek expected but Moore’s Law of Transistors and ever better computers halving in size or doubling in power every couple years does seem to be done. That said, progress continues if slower, and we are seeing commercial production of chips with transistors in the single digits of nanometers, with experimental chips down to about 2 nanometer transistors. Silicon crystals generally are just over half a nanometer across, with nearest neighbors at about a quarter of nanometer, so it's hard to imagine this getting much smaller.
Other crystals aren’t really much smaller either – for instance the hexagonally-spaced carbon atoms in graphene are .142 nanometers apart. Graphene also offers a pathway toward mechanical computing, where we replace the electric switch of a transistor with a super-tiny mechanical switch. None of these seem to offer paths to much smaller computer chips but that isn’t necessarily a big deal. Our best supercomputers are building-sized still and run on a megawatt of power, while being parallel in processing power to a human brain, which is vastly smaller and runs on about 10 watts. Our chips are 2-dimensional powerhogs, so switching into more power and heat efficient methods, and ones more 3D, is likely to be the pathway to faster computers that seem small. Existing chips are already using transistors vastly smaller than a human neuron after all.
In terms of smallest conventional transistor, we are limited by the size of crystals, and spacing between atoms. A chemist would know better, but if I had to guess, metallic hydrogen would probably be the default densest crystal in terms of atoms per volume. Not in terms of mass per volume mind you, that would go to Osmium or far denser degenerate matter states, indeed metallic hydrogen’s density is just a bit higher than water, more than a dozen times less dense than Gold, Osmium, Platinum, Uranium and other dense metals. But hydrogen is the lightest atom, containing a single proton and electron, so both Solid hydrogen – which is just a bit less dense than water – and Metallic hydrogen have very tight spacing, around an angstrom, or tenth of a nanometer. I’m not sure how you’d make a semiconductor out of these, maybe by doping with some other small nuclei or even deuterium or tritium, but you’d have to do it at ultra-cold temperatures, which admittedly is awesome for computing anyway, but not handy for pocket computers, maybe ones wrapped in aerogel to keep them cold. Incidentally the current record for coldest temperature was set earlier this year by physicists in Germany, on a quantum gas, which they dropped to 38 trillionths of a Kelvin.
For folks familiar with the Landauer Limit of temperature and computing that we so often discuss in our Civilizations at the End of Time series, that insanely cold new record would permit computer processing or digital intelligence 8 trillion times more efficient than room temperature. Getting back to Metallic Hydrogen for a quick moment, this material still seems to hold the potential as the most power-dense chemical fuel for rockets or engines in general, and the ability to mass manufacture and store it would be incredible for both rockets and more mundane purposes. We would have to make it though, mining it from Jupiter’s Core wouldn’t seem viable.
See our episode Reusable Rockets and Metallic Hydrogen for more on that. Before we leave materials at ultra-cold temperatures, I should mention that Superconductors have left those temperatures themselves. And we do finally have a room temperature superconductor, or close enough, operating at 15 celsius or 59 fahrenheit. It is also made of the utterly mundane materials of hydrogen, carbon, and sulfur, so not a cost issue to produce. Unfortunately it doesn’t superconduct until it reaches pressures you’d expect to find in Jupiter’s core, not on Earth’s surface, with the temperature it could superconduct at, rising with pressure until reaching 15 Celsius at 267 Gigapascals, over a couple million standard atmospheres. On the other hand we might be able to pull off pressures like that inside one of our superstrong tube materials like carbon nanotubes, the rolled cylinder form of graphene, and a lot of 2D materials are emerging, many of which have fascinating electrical properties, like Stanene, which might turn out to be a room temperature superconductor, though has been hard to make, and it is like Graphene only made of Tin not carbon.
Last I checked, Graphene was the most conductive material at room temperature and regular pressure, and silver keeps the role of highest conductivity of a mundane metal at standard pressure and temperature. Incidentally we shouldn’t rule out materials that not only need high-pressure to create but maintain, as we’ve gotten very good with using lasers to create tiny spots of ultra-high pressure. The University I went grad school at was very big on Liquid Crystals – these are crystals that act as a liquid but have non-symmetric shapes that can line up when temperature changes or electric fields are imposed, and thus can have varying optical properties – giving them great value when utilised in TVs and computer monitors, and it occurs to me that you might have substances that do the same for specific wavelengths of light – changing some property or another, not just optical but hardness or viscosity or permeability – and millions of tiny lasers might let you pixelate that at the small scale. Not a current tech or prediction, just throwing that one out there, materials that responded by changing properties under the wavelength or radiant pressure of a laser beam..
Speaking of viscosity, Superfluid Helium still holds the record for lowest viscosity of any liquid, being zero, as superfluids are the viscosity equivalent of superconductors and generally need even lower temperatures. This has that creepy effect of making thin films of Superfluid climb up and out of beakers, which is only possible by that utter lack of viscosity. Needless to say any superfluid that could exist at Room temperature or engine temperatures would have some amazing uses and in roles besides lubrication. The solid material with the lowest friction, slippier even than Teflon, is BAM, a mix of Boron, Aluminum, and Magnesium that not only has just 40% of the frictional coefficient of Teflon, but is very nearly as hard as diamond.
Needless to say, an ultra-hard material more slippery than ice is probably not a good option for ice skating rinks, especially for skaters like myself who tend to slip and fall on our backsides a lot, but might be an easier option for summer time rinks, and obviously has tons of other less athletic uses, like engine pistons. That’s a non-exhaustive list of a lot of material properties and their current advances and record-holders, and I thought we were talking a lot about things made at ultra-high pressures, so I thought we would flip around to looking at materials made in a vacuum or made in zero-gravity for a moment. When it comes to space, our interests these days are mostly in what ultra-lightweight material can handle radiation damage and the general corrosive effects of space dust and unfiltered sunlight, and improvements in those materials offers us a path to better space ships and space stations, but space stations may be the place we do a lot of manufacturing in the future. We discussed a lot of these in our episode Kickstarting Space Industry, but one I’d point to for today, as we were discussing ever-smaller semiconductors, is that you can grow semiconductors with far fewer defects, in microgravity.
It is very hard to make atomic scale patterns of elements to allow supersmall semiconductors because almost anything can throw-off clean defect-free formation, and gravity is no friend to this process. So space offers us much cheaper and better crystals, and semiconductors are just one such example. Cost-wise, transistors and computer chips are already much more valuable than their weight in gold.
So the time and fuel spent running them up and down from orbit isn’t as prohibitive as it would be for other current purposes. Interestingly there are materials that will be handy for space we might not tend to expect, like a material that fluoresces or one that gets smelly when cracks emerge in them to indicate weaknesses in that material, for in a spaceship hull or helmet. Much like we put artificial scents in fuel gases to make people notice leaks, films of undercoating on materials that when exposed to oxygen or light grabbed our attention through glowing or stinking has a shocking number of real world applications, and such materials are now being explored for those applications.
One of the most obvious is maintenance, as vast amounts of money are wasted and injuries un-avoided from folks simply not knowing a device or structure they are nearby is needing some routine maintenance. Someone once joked to me that the upside of a sewer pipe over a water pipe is that when they started leaking people noticed and reported it, and that is one application of scratch and sniff tech, damaged components getting smelly or glowing. Needless to say, while Smell-o-vision as a way of augmenting audio and video has been a joke for decades, digital or material generation of smells or flavors is also something of great value if achievable.
Not really something I hear much about in serious discussion, but same as hearing-loss really hurts quality of life, loss of taste and smell does too, and smell and taste simulation or stimulation has applications in near-future quality of life issues, not just really good virtual reality. It could make prosthetic options available for damage to those types of organs, which is common. It's also a reminder that not all material advances involve some property like strongest, coldest, lightest, densest, and so on, but properties more biological. As these last couple years have shown us, rich as they have been in Grandfather Nurgle’s Blessings, material advances in biotechnology will matter a lot too in preventing disease.
I mentioned prosthetics a moment ago and we are constantly battling the rejection issues we have with prosthetics, implants, and biotechnology in general, and that’s where materials which minimize rejection or prevent biofilm developing to allow growing infections can come in handy. Polyethylene glycol is one of the most widely-used polymer coatings for preventing bacterial adhesion, as are titanium nanotubes. Sadly we haven’t got time to go into discussion on these or some other neat options like Programmable matter, which will be one of our poll options, which is mostly not about robots – rather it’s stuff like liquid crystals, folding proteins, quantum wells, and metamaterials, but it does include a couple robot examples like claytronics, which is essentially very tiny and simple machines designed to clump up to form more complex machines like a person molding clay in clay animation.
It's not the same as nanoclay, just a similarity of name, but that’s another interesting material hitting the commercial and ecological realms. Nanoclays are tiny particles of mineral silicates that are relatively easy to make and which have been explored in recent years for their use, when incorporated into polymers, of improved mechanical, electrical, and thermal properties, as well as flame and corrosion resistance, offering potentially superior alternatives to coatings that are widely-used today. Coatings on materials to alter their properties or improve them is nothing new in chemistry, but ultra-thin coatings, bordering on the two-dimensional, is also an emerging option and takes us to 2D materials. Now there’s way too much on this topic for us to do justice to it today, so it will be a poll option for a future episode too, but graphene was just the first of many emerging quasi-two-dimensional materials, one-atom thick sheets, many of which also have fascinating properties when stacked two layers thick or with a second layer of a different 2D material. But four recent developments I wanted to mention quickly are boron nitride, sometimes nicknamed ‘white graphene’ which when stacked with another sheet of itself has ferroelectric properties showing promise as an option for ultra-dense and quick computer memory.
Boron Nitride has also been heavily used in quantum computing, and recent use of it in tandem with gold films has been enhancing the brightness of qubits to make ‘seeing’ them far easier. We also have these materials being used to make ultra-tiny electrodes, which would be able to be used for many purposes but for channel regulars probably the most interesting would be that you could use it to do a neural lace good enough to attach to every single neuron individually, so a powerful development for mind-machine interfaces and mind augmentation. Lastly, for today anyway, a mix of tungsten selenide 2D sheets with black phosphorus sheets is giving us a polarized and photovoltaic material, meaning a solar panel light and flexible enough to be woven into your clothing to provide power to your devices or woven into pretty much anything else. There are a lot of materials we barely had a chance to touch on, some not even all that high-tech and many in use now and often strange, like Blood Bricks – which are exactly what they sound like, a building brick made out of sand and blood – and Pykrete, and ultra-strong material made of ice and fibrous materials, usually sawdust.
Wood may be waning as a building material after a period of sharp lumber cost increases but wood may even have a role in future skyscrapers. Plyscrapers, as some dub them, utilizing cross-laminated timbers, have begun to see some use, and are being sold as a quicker and lower-energy cost means of tall construction, one maybe safer ecologically and also weirdly, safer in event of fires than many buildings too. As to how tall you can go, even beyond super-strong materials, we have options like active support that permit the construction of supertall buildings we call Space Towers - see that episode for details.
But folks sometimes ask what might be even stronger than Graphene, and a lot stronger at that. To finish up for today, I thought we would discuss a few of the hypothetical materials that are only theoretical possibilities for now but may one day leave the pages of science fiction novels for science textbooks. One of those is Magmatter, which gets its name from Magnetic Monopoles. Now magnetic monopoles are a topic of hot debate in physics and have been for many years, but if they existed they would represent a particle that only had a north or south pole. Normally a magnet has a north pole and south, and if you cut it in half, you just get a new north and south on each half, much as you would get a new top and bottom on each half. It’s rather hard to imagine cutting an object with a top and bottom in half so that it only had a top on one half, with no bottom, and vice versa on the other half, and the same is true of magnetic monopoles but there’s some decent reason to think they exist in theory, and indeed they are predicted by string theory and most grand unified theories too.
If they exist they would effectively be a very tiny particle, tinier than atoms, and one limit on material strength is atom spacing. As I mentioned earlier, the spacing on graphene for carbon atoms is very small, only .142 nanometers apart, and as an over-simplified example, an electron and proton at this distance from each other pull four times harder on each other than they do if twice as far apart, so it takes four times more force to rip that bond apart, and this is essentially what tensile strength is, tearing apart those bonds between atoms.
It’s all electric and magnetic forces though and so distance matters, and magnetic monopoles are so small they might be spaced to create “Magatoms” millions of times smaller than normal atoms and thus with bonds millions of times stronger, making things like space elevators a breeze to build. Indeed I’ve heard some calculations of this put it as much as a trillion-trillion-trillion times stronger than normal chemical bonds, which if true would let you flat out construct tensile-strength titans like Banks’ Orbitals and Ringworlds. These sort of strengths also open the door to options like Neutronium, which is matter made entirely of neutrons and which is so dense it can absorb neutrinos, though I should note both it and Magmatter are dense the way neutron stars are dense, even single-atom thick sheets, or rather single neutron or magatom thick sheets, are going to be monstrously heavy if monstrously strong, able to withstand direct hits from nukes or even antimatter.
Also monstrously sharp, they should be able to cut basically anything. If we reach to the deeper future and more Clarketech style options, those bordering on magic, we can even imagine materials that are composed of dark matter or interact with it, or weirder options like materials so sharp they can cut space or time. Materials that can take photons and turn them into neutrinos or gravitons, much as we have photovoltaics to turn photons into electricity.
Materials that might be able to generate gravity directionally or even warp space or time directionally, crunching it or sending it as a beam. In a world where superconductors and superfluids were thought impossible only a couple generations back, we probably don’t want to rule out what wonders we might discover hundreds of generations from now, but as we’ve seen today, we don’t have to wait generations to encounter wondrous new advances in Material Science. So today’s topic was as much chemistry as physics and ranged over a broad variety of subdisciplines, but at its core a lot of the material on materials is about those basic chemical reactions and if you’re looking to understand the science behind those better, there is an excellent course, “The Chemical Reaction” over on Brilliant. Now if you’re a regular of this channel or lots of other science channels for that matter you’ve probably heard us talking about why we love Brilliant, and I think for myself and others a lot of it is that Brilliant's the sort of interactive, handson platform we all wish we had when we learning science. And I thought that was worth noting here in the holiday season because so many of us know folks looking to learn science and math, and there really is no better gift than the gift of knowledge.
Brilliant makes an awesome gift for any of the ambitious learners in your life. Whether it's an inquisitive niece, an all-knowing parent, or the neighbor who seems to have everything, I know your curious loved ones of all ages will be excited to grow with Brilliant's interactive learning approach. Brilliant is the hands-down best hands on interactive STEM-learning platform out there which can assist you or loved one in learning concepts by visualizing them and interacting with them, the best way to learn. On Brilliant you can just pick a course you’re interested in and get started, be it the basics or advanced. If you get stuck or make a mistake you can read the explanations to find out more and learn at your own pace.
Knowing and understanding Math, Science, and Computer Science unlocks whole new worlds, and if you’d like to start your journey to them, you can try out Brilliant for free and get 20% off a year of STEM learning, click the link in the description down below or visit: brilliant.org/IsaacArthur. So we’re winding our way towards new years and only have 3 more Thursday’s to go but we also have our Scifi Sunday episode this weekend, December 12th to look at folks staking and jumping claims on asteroid mines and similar, and two weeks after that we’ll have our End of the Month Livestream Q&A, on Sunday, December 26th at 4pm Eastern Time. But first, a week from now we will have a discussion of Vertical Farming, the technology that may let us nourish many billions of people while keeping our planet pristine.
Then we’ll take a look at Escaping the Galaxy the week after that, if we need to get away from someone who has blown up our planet, before closing out the month and the year with a look at the Challenges we will be facing in the next 100 years. Then we will explode into 2022 with a look at using Nuclear Bombs to propel Spaceships. Now if you want to make sure you get notified when those episodes come out, make sure subscribe to the channel, and if you enjoyed the episode, don’t forget to hit the like button and share it with others. If you’d like to help support future episodes, you can donate to us on Patreon, or our website, IsaacArthur.net, and patreon and our website are linked in the episode description below,
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2021-12-10