WEBVTT 00:00:00.000 --> 00:00:03.040 Welcome to the deep dive. Have you ever wondered 00:00:03.040 --> 00:00:06.339 what happens if you take like a single atom, 00:00:06.660 --> 00:00:09.300 say an iron atom, and just fire it into a piece 00:00:09.300 --> 00:00:12.500 of solid plastic at supersonic speeds? Most people 00:00:12.500 --> 00:00:14.820 probably assume it just bounces off or, you know, 00:00:14.960 --> 00:00:17.059 maybe shatters the plastic completely. Right, 00:00:17.100 --> 00:00:19.100 but it actually doesn't do either of those things. 00:00:19.640 --> 00:00:23.019 It vaporizes this perfectly straight eight nanometer 00:00:23.019 --> 00:00:26.379 tunnel of just localized destruction. and then 00:00:26.379 --> 00:00:28.760 that tunnel freezes in a fraction of a nanosecond. 00:00:28.879 --> 00:00:30.980 It's incredibly violent, but at the same time, 00:00:31.100 --> 00:00:33.799 it's incredibly precise. Yeah, and that's exactly 00:00:33.799 --> 00:00:36.140 our mission for today. We have this stack of 00:00:36.140 --> 00:00:38.479 really dense technical sources on a field called 00:00:38.479 --> 00:00:41.299 ion track technology, and we're going to explore 00:00:41.299 --> 00:00:44.399 how scientists take these wild, uncontrollable 00:00:44.399 --> 00:00:46.939 subatomic collisions and basically tame them. 00:00:47.039 --> 00:00:50.920 turning them into essentially the ultimate microscopic 00:00:50.920 --> 00:00:53.460 sculpting tool. Exactly. By the end of this deep 00:00:53.460 --> 00:00:55.500 dive, you will see how understanding these tiny 00:00:55.500 --> 00:00:57.920 little atomic bullet holes lets us build everything 00:00:57.920 --> 00:01:00.920 from like hypersensitive virus detectors to the 00:01:00.920 --> 00:01:03.500 actual spintronic components inside modern computer 00:01:03.500 --> 00:01:06.260 hard drives. It's really a profound shift in 00:01:06.260 --> 00:01:08.739 how we approach manufacturing at the nanoscale. 00:01:08.840 --> 00:01:11.219 Oh, for sure. Now, the source material is pretty 00:01:11.219 --> 00:01:13.180 heavy on the physics. We're talking Rutherford 00:01:13.180 --> 00:01:16.180 backscattering spectrometry, columnar chainstitions, 00:01:16.640 --> 00:01:19.079 thermal diffusivity. Lots of big words. Lots 00:01:19.079 --> 00:01:22.319 of big words. But at its core, I promise you 00:01:22.319 --> 00:01:25.260 this is just a thrilling story about controlling 00:01:25.260 --> 00:01:29.370 matter. under extreme stress. Because for decades, 00:01:29.890 --> 00:01:32.349 nanolithography has relied on a top -down approach, 00:01:32.569 --> 00:01:35.549 right? Masking broad areas, etching away bulk 00:01:35.549 --> 00:01:39.129 material. But ion track technology flips that 00:01:39.129 --> 00:01:40.989 whole paradigm. It builds from the inside out. 00:01:41.170 --> 00:01:44.030 Exactly. We are using the kinetic energy of single 00:01:44.030 --> 00:01:46.890 atoms to dictate structural depth and geometry. 00:01:47.629 --> 00:01:50.230 Understanding the why behind these tracks unlocks 00:01:50.230 --> 00:01:52.969 a whole new level of nanotechnology. OK, let's 00:01:52.969 --> 00:01:55.150 unpack this before we can use these microscopic 00:01:55.209 --> 00:01:57.569 tunnels to build a hard drive, we have to look 00:01:57.569 --> 00:01:59.870 at the sheer physics of the formation event itself. 00:01:59.950 --> 00:02:01.969 The initial impact. Right. We're talking about 00:02:01.969 --> 00:02:05.390 a swift heavy ion acting as the projectile. This 00:02:05.390 --> 00:02:07.569 is an atom stripped of its electrons, accelerated 00:02:07.569 --> 00:02:10.770 to a massive velocity. And when it strikes the 00:02:10.770 --> 00:02:13.550 target material, the energy transfer doesn't 00:02:13.550 --> 00:02:16.210 actually happen through direct nuclear impacts. 00:02:16.430 --> 00:02:19.169 It's not atoms smashing into atoms. Wait, really? 00:02:19.560 --> 00:02:21.979 It's not a physical collision. Not exactly. It 00:02:21.979 --> 00:02:24.479 transfers energy through columbic interactions 00:02:24.479 --> 00:02:27.560 with the target's electron cloud. So the heavy 00:02:27.560 --> 00:02:29.979 ion plows through the material and violently 00:02:29.979 --> 00:02:32.460 knocks primary electrons out of their orbit. 00:02:32.520 --> 00:02:35.259 Oh wow. And those primary electrons are ejected 00:02:35.259 --> 00:02:37.360 with so much kinetic energy that they trigger 00:02:37.360 --> 00:02:40.120 a secondary cascade. They start colliding with 00:02:40.120 --> 00:02:42.340 other electrons further out. So it's a localized 00:02:42.340 --> 00:02:44.800 storm of ionization. That's a great way to put 00:02:44.800 --> 00:02:47.759 it. But the crucial factor here is momentum conservation. 00:02:48.219 --> 00:02:51.280 The mass ratio between our projectile -like, 00:02:51.280 --> 00:02:54.219 say, an iron ion and the electrons it's scattering 00:02:54.219 --> 00:02:57.020 is roughly 10 to the fifth power. Meaning the 00:02:57.020 --> 00:03:00.340 iron ion is, what, 100 ,000 times heavier? Exactly. 00:03:00.379 --> 00:03:02.639 So it doesn't even deflect. It maintains a perfectly 00:03:02.639 --> 00:03:05.000 straight trajectory, while the electron cloud 00:03:05.000 --> 00:03:07.840 is essentially just blown outward. Living behind 00:03:07.840 --> 00:03:10.960 a highly charged, highly unstable region along 00:03:10.960 --> 00:03:13.490 that primary path. What's fascinating here is 00:03:13.490 --> 00:03:16.270 how that instability resolves. Wait, wait, let 00:03:16.270 --> 00:03:18.740 me jump in because... What's fascinating here 00:03:18.740 --> 00:03:20.939 is actually the thermal spike model. That's how 00:03:20.939 --> 00:03:24.240 it resolves. Oh, right. The heat. Yes. All of 00:03:24.240 --> 00:03:26.840 those secondary electron collisions generate 00:03:26.840 --> 00:03:30.759 intense localized atomic vibration. The kinetic 00:03:30.759 --> 00:03:33.340 energy rapidly converts into thermal energy. 00:03:33.599 --> 00:03:35.819 Remember talking fast, right? Like unimaginably 00:03:35.819 --> 00:03:39.419 fast. Within 10 to the minus 14 seconds, the 00:03:39.419 --> 00:03:41.400 temperature inside that nanometer scale core 00:03:41.400 --> 00:03:44.240 spikes violently, shooting well above the melting 00:03:44.240 --> 00:03:46.840 point of the target material. It's almost like 00:03:46.889 --> 00:03:49.849 Imagine you've got a 10 -ton bowling ball. Right? 00:03:50.250 --> 00:03:52.629 And you fire it at supersonic speeds through 00:03:52.629 --> 00:03:55.150 a giant ball pit. I love that visual. The bowling 00:03:55.150 --> 00:03:57.949 ball flies perfectly straight, completely unbothered, 00:03:57.990 --> 00:04:00.610 while the plastic balls scatter wildly everywhere. 00:04:01.030 --> 00:04:03.629 And it's basically melting this momentary tunnel 00:04:03.629 --> 00:04:06.150 of heat that just instantly freezes behind it. 00:04:06.270 --> 00:04:08.810 That is precisely it. It creates a microscopic 00:04:08.810 --> 00:04:11.169 cylinder of liquid melt right through the solid 00:04:11.169 --> 00:04:13.590 lattice. But because the volume of that liquid 00:04:13.590 --> 00:04:16.410 is so tiny, the heat dissipates into the surrounding 00:04:16.410 --> 00:04:19.819 cold material almost instantly. rate is extreme. 00:04:20.360 --> 00:04:23.019 So extreme that the molten atoms simply do not 00:04:23.019 --> 00:04:25.759 have time to reorganize themselves into their 00:04:25.759 --> 00:04:28.759 original stable crystalline structure. They just 00:04:28.759 --> 00:04:32.199 rapidly quench. Exactly. The material freezes 00:04:32.199 --> 00:04:35.360 in an amorphous disordered state. The density 00:04:35.360 --> 00:04:37.819 actually changes, creating a permanent structural 00:04:37.819 --> 00:04:41.439 deficit, a latent track. Literally frozen disorder. 00:04:41.600 --> 00:04:44.410 Yep. And because that density deficit is a permanent 00:04:44.410 --> 00:04:47.470 physical change, researchers can map these eight 00:04:47.470 --> 00:04:50.629 nanometer scars later. They use tools like transmission 00:04:50.629 --> 00:04:53.750 electron microscopy or Rutherford backscattering 00:04:53.750 --> 00:04:56.370 spectrometry to see how lighter ions scatter 00:04:56.370 --> 00:04:58.649 off the disordered lattice. But the sources make 00:04:58.649 --> 00:05:01.310 it very clear that you cannot just fire these 00:05:01.310 --> 00:05:04.110 heavy ions into any arbitrary material and expect 00:05:04.110 --> 00:05:06.569 a clean usable track. Right. The canvas matters 00:05:06.569 --> 00:05:09.259 just as much as the projectile. The target material 00:05:09.259 --> 00:05:12.339 has to meet highly specific thermodynamic criteria. 00:05:12.839 --> 00:05:15.600 And the first rule is homogeneity. The material 00:05:15.600 --> 00:05:18.139 must be uniform. Which is why optically translucent 00:05:18.139 --> 00:05:21.259 polymers like polycarbonate are ideal. Right. 00:05:21.300 --> 00:05:24.939 But if you use a grain polymer like polytetrafluoroethylene 00:05:24.939 --> 00:05:27.870 teflon, doesn't work. Because the local density 00:05:27.870 --> 00:05:30.569 variations of the pristine Teflon completely 00:05:30.569 --> 00:05:34.089 mask the density deficit of the track. The track 00:05:34.089 --> 00:05:36.490 just gets lost in the background noise of the 00:05:36.490 --> 00:05:39.670 material's own texture. Ah, okay. But there's 00:05:39.670 --> 00:05:42.329 a more restrictive rule, and it governs electrical 00:05:42.329 --> 00:05:46.050 and thermal conductivity. Insulators, like minerals, 00:05:46.269 --> 00:05:49.589 glasses, and polymers, work beautifully. but 00:05:49.589 --> 00:05:52.189 highly conductive metals do not work well at 00:05:52.189 --> 00:05:55.089 all. No, they generally fail to form usable tracks. 00:05:55.370 --> 00:05:57.569 So wait, shooting a piece of solid metal with 00:05:57.569 --> 00:06:00.209 a high -energy ion doesn't work because the metal 00:06:00.209 --> 00:06:01.970 is actually too good at conducting the heat away? 00:06:02.129 --> 00:06:04.629 That's exactly it. The thermal diffusivity is 00:06:04.629 --> 00:06:07.319 coupled with their electrical conductivity. It's 00:06:07.319 --> 00:06:09.439 like trying to melt a specific dot on a massive 00:06:09.439 --> 00:06:11.779 block of copper versus a block of wax. The copper 00:06:11.779 --> 00:06:14.040 just pulls the heat away instantly. Exactly. 00:06:14.399 --> 00:06:17.360 Metals have this highly mobile sea of free electrons, 00:06:17.620 --> 00:06:19.939 so those electrons carry the thermal energy away 00:06:19.939 --> 00:06:22.800 from the impact zone before the localized thermal 00:06:22.800 --> 00:06:25.040 spike ever reaches the threshold required to 00:06:25.040 --> 00:06:27.180 melt the lattice. It just dissipates. The heat 00:06:27.180 --> 00:06:29.759 bleeds out too fast. For the molten cylinder 00:06:29.759 --> 00:06:32.720 to form, the material must trap the heat locally. 00:06:33.199 --> 00:06:35.790 That is why insulators work. Okay, that makes 00:06:35.790 --> 00:06:38.089 total sense. You also need low atomic mobility 00:06:38.089 --> 00:06:40.689 in the solid state, because if the atoms can 00:06:40.689 --> 00:06:43.750 easily migrate over time, the density contrast 00:06:43.750 --> 00:06:46.610 gradually diffuses. The track literally heals 00:06:46.610 --> 00:06:48.930 itself. The material essentially patches its 00:06:48.930 --> 00:06:51.750 own scar. Right. And this brings us to radiation 00:06:51.750 --> 00:06:54.470 sensitivity, which is why polymers are highlighted 00:06:54.470 --> 00:06:56.810 as exceptionally good candidates. Because they 00:06:56.810 --> 00:06:59.449 react so well to that secondary electron cascade. 00:06:59.649 --> 00:07:02.129 Precisely. And the ultra -hot core of the track, 00:07:02.269 --> 00:07:05.519 the energy induces chain -cision. It literally 00:07:05.519 --> 00:07:08.379 chops the long carbon backbones of the polymer 00:07:08.379 --> 00:07:12.079 into shorter degraded fragments. But in the surrounding 00:07:12.079 --> 00:07:14.860 halo where the energy is dissipating, it induces 00:07:14.860 --> 00:07:17.560 crosslinking, right? Yes, forging new bonds between 00:07:17.560 --> 00:07:20.019 adjacent polymer chains. So you are left with 00:07:20.019 --> 00:07:22.939 a highly degraded pulverized core tightly confined 00:07:22.939 --> 00:07:25.759 by a hardened cross -linked shell. Which is a 00:07:25.759 --> 00:07:27.839 perfectly packaged template for nanoscale engineering. 00:07:28.060 --> 00:07:31.420 It is. But you have to remember, relying on background 00:07:31.420 --> 00:07:34.439 cosmic radiation or weak natural isotopes to 00:07:34.439 --> 00:07:37.339 create these templates is, well, it's insufficient 00:07:37.339 --> 00:07:39.319 for industrial applications. Right, because now 00:07:39.319 --> 00:07:42.649 we need the gun. Yeah. How exactly do scientists 00:07:42.649 --> 00:07:46.350 generate these swift, heavy ions? Well, there 00:07:46.350 --> 00:07:49.009 are alpha and fission sources, like Halifornium 00:07:49.009 --> 00:07:52.850 -252 or Americium -241. They're weak, cheap, 00:07:52.990 --> 00:07:55.550 and compact. Safe to handle, but they only penetrate 00:07:55.550 --> 00:07:58.589 about 15 micrometers. So if you are mass producing, 00:07:58.589 --> 00:08:01.810 say, commercial water filters, a nuclear reactor 00:08:01.810 --> 00:08:03.889 providing a shower of fission fragments might 00:08:03.889 --> 00:08:06.839 suffice. Sure, but to achieve deep parallel tracks 00:08:06.839 --> 00:08:08.939 without leaving the material highly radioactive, 00:08:09.379 --> 00:08:12.720 you need the big guns. Heavy ion particle accelerator. 00:08:12.899 --> 00:08:15.319 Exactly. These machines fire parallel beams of 00:08:15.319 --> 00:08:17.560 heavy ions at high luminosity. We're talking 00:08:17.560 --> 00:08:20.160 shooting billions of ions per second to create 00:08:20.160 --> 00:08:22.319 tracks up to hundreds of micrometers deep. But 00:08:22.319 --> 00:08:24.459 the true breakthrough, and this blew my mind 00:08:24.459 --> 00:08:27.240 in the reading, is single ion irradiation. Oh, 00:08:27.240 --> 00:08:29.579 it's incredible. Accelerators can be throttled 00:08:29.579 --> 00:08:33.039 down to emit a severely weak beam. And they put 00:08:33.039 --> 00:08:36.779 a detector behind the target foil. The absolute 00:08:36.779 --> 00:08:39.580 microsecond, a single ion, penetrates the target 00:08:39.580 --> 00:08:42.120 and hits the detector. A feedback loop physically 00:08:42.120 --> 00:08:44.519 deflects the accelerator beam. It shuts it down 00:08:44.519 --> 00:08:47.500 instantly. It's completely wild to think we have 00:08:47.500 --> 00:08:50.360 machines that can fire literally one atomic bullet 00:08:50.360 --> 00:08:53.350 and then immediately power down. We're talking 00:08:53.350 --> 00:08:56.230 about sniper -level precision at the submicroscopic 00:08:56.230 --> 00:08:58.929 scale. And with ion microbeams, they can actively 00:08:58.929 --> 00:09:01.529 scan a surface, scribing individual tracks with 00:09:01.529 --> 00:09:04.669 an aiming precision of one micrometer. We aren't 00:09:04.669 --> 00:09:06.830 just blasting materials randomly anymore. We're 00:09:06.830 --> 00:09:09.110 intentionally placing single atoms. Exactly. 00:09:09.210 --> 00:09:11.690 We are defining structural depth by the ion's 00:09:11.690 --> 00:09:13.690 range, rather than the thickness of the material 00:09:13.690 --> 00:09:15.929 itself. Here's where it gets really interesting, 00:09:16.169 --> 00:09:18.149 though. Because once the ion has passed through, 00:09:18.289 --> 00:09:21.309 you only have a latent track. It's just a region 00:09:21.309 --> 00:09:24.200 of damn - material. That pulverized core of chopped 00:09:24.200 --> 00:09:26.899 polymer chains is still solid material. Right. 00:09:27.019 --> 00:09:28.899 It's like writing a message in invisible ink. 00:09:29.200 --> 00:09:31.419 The track is there, but the chemical etching 00:09:31.419 --> 00:09:34.080 is the developer that reveals it, literally digging 00:09:34.080 --> 00:09:37.000 out a microscopic tunnel. We call that selective 00:09:37.000 --> 00:09:39.960 ion etching. You immerse the material in a wet 00:09:39.960 --> 00:09:42.240 etchant, typically a strong alkali like sodium 00:09:42.240 --> 00:09:44.879 hydroxide. And the sodium hydroxide eats the 00:09:44.879 --> 00:09:48.240 damaged track core much faster than the pristine 00:09:48.240 --> 00:09:51.179 surrounding material. Because it hydrolyzes those 00:09:51.179 --> 00:09:53.940 damaged polymer bonds at a drastically accelerated 00:09:53.940 --> 00:09:57.080 rate. And remember that hardened cross -linked 00:09:57.080 --> 00:09:59.080 halo we discussed? Yeah, the shell around the 00:09:59.080 --> 00:10:01.820 core. That shell severely restricts the lateral 00:10:01.820 --> 00:10:04.580 etching. The etchant prefers to dig straight 00:10:04.580 --> 00:10:07.279 down the track. Leaving behind these empty cones 00:10:07.279 --> 00:10:10.679 or cylinders. But to push the geometry even further, 00:10:11.000 --> 00:10:12.960 they use something called surfactant -enhanced 00:10:12.960 --> 00:10:16.279 etching. Yes. You introduce amphiphilic molecules 00:10:16.279 --> 00:10:18.980 into the etchant. These molecules self -organize 00:10:18.980 --> 00:10:21.179 into monolayers along the walls of the newly 00:10:21.179 --> 00:10:23.980 excavated pore. They act as a chemical shield, 00:10:24.240 --> 00:10:26.179 basically blocking the acid from attacking the 00:10:26.179 --> 00:10:28.659 side walls so it only digs downward. And the 00:10:28.659 --> 00:10:30.600 geometry you can achieve with that shielding 00:10:30.600 --> 00:10:33.879 is extreme. You can get perfect barrel or cylindrical 00:10:33.879 --> 00:10:37.659 shapes with insane aspect ratios, meaning the 00:10:37.659 --> 00:10:40.080 depth divided by the width of up to 10 ,000 to 00:10:40.080 --> 00:10:43.200 1. That's wild. And then comes replication, which 00:10:43.200 --> 00:10:46.370 is just pouring liquid metal. into that tunnel 00:10:46.370 --> 00:10:49.309 to make a 3D cast. Well, electroplating specifically. 00:10:49.690 --> 00:10:51.649 You place a cathode on one side of the porous 00:10:51.649 --> 00:10:54.570 membrane and an anode on the other. Positive 00:10:54.570 --> 00:10:57.350 metal ions are pulled into the empty pores. They 00:10:57.350 --> 00:11:00.190 hit the cathode, pick up electrons, and grow 00:11:00.190 --> 00:11:02.710 a solid nanowire from the bottom up. But the 00:11:02.710 --> 00:11:05.250 crucial nuance here is the speed of deposition. 00:11:05.929 --> 00:11:08.409 Rapid deposition creates polycrystalline wires, 00:11:08.590 --> 00:11:10.549 which have lots of grain boundaries and high 00:11:10.549 --> 00:11:13.009 electrical resistance. But if you go slow? Slow 00:11:13.009 --> 00:11:15.870 deposition creates highly efficient single crystalline 00:11:15.870 --> 00:11:18.429 wires and if you alternate the electrical polarity 00:11:18.429 --> 00:11:20.730 during the process using different metal salts 00:11:20.730 --> 00:11:23.309 you get segmented nanowires like alternating 00:11:23.309 --> 00:11:26.090 disks of copper and cobalt stacked together exactly 00:11:26.090 --> 00:11:28.570 and you can even shoot ions from different angles 00:11:28.570 --> 00:11:30.929 to create multi -angular channels when those 00:11:30.929 --> 00:11:33.149 intersect and you fill them with metal and dissolve 00:11:33.149 --> 00:11:35.990 the polymer you get interpenetrating freestanding 00:11:35.990 --> 00:11:39.769 3d nanowire networks a literal three -dimensional 00:11:39.769 --> 00:11:42.669 mesh of nanowires okay so think about how this 00:11:42.669 --> 00:11:45.750 impacts you the listener We've made tiny holes 00:11:45.750 --> 00:11:48.809 and tiny wires. Why does this matter? How do 00:11:48.809 --> 00:11:51.490 these structures end up in our daily lives? Let's 00:11:51.490 --> 00:11:54.370 start with geology. Geology is fascinating because 00:11:54.370 --> 00:11:57.909 ion tracks act as geological clocks. Right, through 00:11:57.909 --> 00:12:00.769 fish and track dating. Yes. Because minerals 00:12:00.769 --> 00:12:02.970 have that ultra -low atomic mobility we talked 00:12:02.970 --> 00:12:05.830 about, natural ion tracks from trace uranium 00:12:05.830 --> 00:12:08.429 fission remain perfectly unaltered for millions 00:12:08.429 --> 00:12:11.350 of years. Geologists can etch a rock, count the 00:12:11.350 --> 00:12:13.350 tracks under a microscope, and read its exact 00:12:13.350 --> 00:12:16.429 thermal history. But we also pivot from measuring 00:12:16.429 --> 00:12:19.289 deep time to actively measuring human biology. 00:12:19.580 --> 00:12:22.460 like medical diagnostics. Specifically, the Coulter 00:12:22.460 --> 00:12:24.620 counter microchannels. These are used to size 00:12:24.620 --> 00:12:27.000 and count individual red blood cells, bacteria, 00:12:27.200 --> 00:12:29.419 and viruses. By using electrical resistance drops, 00:12:29.639 --> 00:12:31.960 right? Exactly. You have a membrane with a single 00:12:31.960 --> 00:12:34.620 etched pore fluid on both sides and a constant 00:12:34.620 --> 00:12:36.980 voltage running through it. When a virus passes 00:12:36.980 --> 00:12:39.539 through the hole, it physically displaces the 00:12:39.539 --> 00:12:41.980 conductive fluid. So the particle acts as a tiny 00:12:41.980 --> 00:12:44.720 insulator. The electrical resistance momentarily 00:12:44.720 --> 00:12:47.279 spikes. And you can calculate the exact size 00:12:47.279 --> 00:12:49.759 of the virus based on that spike. It's a highly 00:12:49.759 --> 00:12:52.600 accurate, label -free method for sizing pathogens. 00:12:53.399 --> 00:12:56.480 But biologists go even further. They chemically 00:12:56.480 --> 00:12:59.019 clad the channel walls to recognize specific 00:12:59.019 --> 00:13:02.240 DNA fragments, turning them into active biosensors. 00:13:02.399 --> 00:13:04.980 And when the target DNA binds to the wall, it 00:13:04.980 --> 00:13:07.600 literally shrinks the channel. Yes. The volume 00:13:07.600 --> 00:13:10.200 decreases, restricting the fluid flow, which 00:13:10.200 --> 00:13:12.480 registers as a permanent change in resistance. 00:13:13.019 --> 00:13:16.080 It acts as a hypersensitive detector. You immediately 00:13:16.080 --> 00:13:18.970 know that specific genetic sequences So when 00:13:18.970 --> 00:13:21.509 you need a hyper -specific blood test, you might 00:13:21.509 --> 00:13:23.509 be relying on a technology born from shooting 00:13:23.509 --> 00:13:25.490 a high -speed atom through a piece of plastic. 00:13:25.679 --> 00:13:28.100 And it even applies to the tech we use every 00:13:28.100 --> 00:13:30.679 day, like spintronics and magnetic sensors. This 00:13:30.679 --> 00:13:33.159 is where those segmented, alternating cobalt 00:13:33.159 --> 00:13:36.000 and copper nanowires come in. They engineer a 00:13:36.000 --> 00:13:38.399 device capable of giant magnetor resistance, 00:13:38.559 --> 00:13:40.679 or GMR. Without getting too deep into quantum 00:13:40.679 --> 00:13:42.879 mechanics, this relies on the spin of the electrons, 00:13:43.000 --> 00:13:45.899 right? Right. Without a magnetic field, the cobalt 00:13:45.899 --> 00:13:48.820 layers naturally settle into an anti -parallel 00:13:48.820 --> 00:13:51.340 alignment, pointing in opposite directions. Which 00:13:51.340 --> 00:13:53.840 causes a massive traffic jam for the electrons 00:13:53.840 --> 00:13:56.929 trying to pass through. high electrical resistance. 00:13:57.149 --> 00:13:59.610 But when an external magnetic field is applied, 00:13:59.850 --> 00:14:02.590 it forces all the cobalt layers into parallel 00:14:02.590 --> 00:14:05.710 alignment. The resistance drastically plummets. 00:14:06.250 --> 00:14:09.610 This binary shift is the exact foundational technology 00:14:09.610 --> 00:14:12.110 used in the reading heads of magnetic hard drives. 00:14:12.250 --> 00:14:14.350 So every time you save a file on a hard drive, 00:14:14.490 --> 00:14:16.710 you're using this. If we connect this to the 00:14:16.710 --> 00:14:18.909 bigger picture, these aren't just passive holes. 00:14:18.990 --> 00:14:22.110 They are dynamic, environmentally responsive 00:14:22.110 --> 00:14:25.269 machines. Take the pH sensor application, for 00:14:25.269 --> 00:14:27.389 instance. Oh, and this part. In a narrow track, 00:14:27.529 --> 00:14:29.970 the walls inherently carry a negative surface 00:14:29.970 --> 00:14:32.669 charge, which attracts a dense cloud of positive 00:14:32.669 --> 00:14:35.210 ions from the fluid passing through. Making the 00:14:35.210 --> 00:14:37.690 perimeter highly conductive. Right. But at a 00:14:37.690 --> 00:14:40.690 low pH, meaning high acidity, the surface charge 00:14:40.690 --> 00:14:43.710 neutrality kicks in. The extra protons neutralize 00:14:43.710 --> 00:14:46.470 the walls, the positive cloud dissipates, and 00:14:46.470 --> 00:14:48.889 that conductive layer completely vanishes. So 00:14:48.889 --> 00:14:51.649 the pore actively adapts its electrical properties 00:14:51.649 --> 00:14:54.330 based on the acidity of its environment. It's 00:14:54.330 --> 00:14:57.549 a dynamic machine. Exactly. And the source also 00:14:57.549 --> 00:15:00.990 mentions smart textures. Tracks etched at a steep 00:15:00.990 --> 00:15:03.889 angle, coated with hydrophobic material, become 00:15:03.889 --> 00:15:06.789 super hydrophobic asymmetric surfaces. They act 00:15:06.789 --> 00:15:09.570 like microscopic ratchets. If you just introduce 00:15:09.570 --> 00:15:12.629 random ambient vibration, the surface literally 00:15:12.629 --> 00:15:15.690 converts that vibration into uniform forward 00:15:15.690 --> 00:15:18.230 physical movement of water droplets. It's engineering 00:15:18.230 --> 00:15:21.250 at the absolute limits of physics. So what does 00:15:21.250 --> 00:15:23.929 this all mean? We started with the violent kinetics 00:15:23.929 --> 00:15:26.549 of a swift heavy ion slamming into a polymer. 00:15:27.269 --> 00:15:29.350 We looked at how the thermal spike model causes 00:15:29.350 --> 00:15:31.750 rapid quenching into frozen disorder. And by 00:15:31.750 --> 00:15:34.049 selecting the right insulators, we can etch and 00:15:34.049 --> 00:15:36.730 electroplate those tracks into extreme geometries. 00:15:37.049 --> 00:15:39.600 Exactly. We journeyed from a subatomic collision 00:15:39.600 --> 00:15:42.399 to nanotech sensors, hard drive components, and 00:15:42.399 --> 00:15:44.820 medical tools. Destruction at the atomic level 00:15:44.820 --> 00:15:47.519 is basically the key to our most precise creations. 00:15:47.720 --> 00:15:49.840 It really is, but it raises an important question, 00:15:50.019 --> 00:15:52.539 synthesizing two vastly different concepts we 00:15:52.539 --> 00:15:54.480 discussed today. Okay, lay it on me. We know 00:15:54.480 --> 00:15:57.120 natural ion tracks in minerals act as immensely 00:15:57.120 --> 00:16:00.080 stable geological clocks for millions of years, 00:16:00.419 --> 00:16:02.580 and we know man -made tracks can be engineered 00:16:02.580 --> 00:16:05.419 into highly reactive biosensors or thermoresponsive 00:16:05.419 --> 00:16:08.220 hydrogels. Right. What if we combine these two 00:16:08.220 --> 00:16:11.460 concepts? Could we intentionally engineer synthetic, 00:16:12.000 --> 00:16:14.559 data -encoded geological clocks in artificial 00:16:14.559 --> 00:16:17.879 material? No. Microscopic time -tapses of our 00:16:17.879 --> 00:16:20.240 current biological or atmospheric environment. 00:16:20.620 --> 00:16:23.159 We could design them to remain completely dormant 00:16:23.159 --> 00:16:26.360 and utterly stable, far -outlasting digital storage 00:16:26.360 --> 00:16:29.139 or written records. Only to naturally activate 00:16:29.139 --> 00:16:31.779 and be read millions of years from now by whoever, 00:16:32.120 --> 00:16:35.299 or whatever, finds them in the geological strata. 00:16:35.370 --> 00:16:38.090 a diagnostic message in a bottle etched into 00:16:38.090 --> 00:16:40.490 the atomic structure of an artificial rock. That 00:16:40.490 --> 00:16:42.570 is a deeply provocative thought to leave you 00:16:42.570 --> 00:16:44.169 with. Thank you for joining us on this custom 00:16:44.169 --> 00:16:46.690 deep dive into ion track technology. The next 00:16:46.690 --> 00:16:49.889 time you save a file or just look closely at 00:16:49.889 --> 00:16:52.870 a piece of smooth plastic, consider the nanoscale 00:16:52.870 --> 00:16:55.450 architecture hidden inside. Keep questioning 00:16:55.450 --> 00:16:57.409 those invisible forces shaping your world.