Molding a Microlens Array

[@BreakingTaps]

**Addendum** - I meant 4mm^2 (2x2mm) in the intro, although I later measured and it's actually 1x1mm. Oops! Sorry for the confusion, I phrased it poorly :)

[@Alexagrigorieff]

A similar process is used to etch diamond. A nickel or iron mask is deposited. Under high temperatures in H2 atmosphere, carbon dissolves in the mask and gets carried away by reacting with hydrogen into CH4.

[@AndroidFerret]

Funny ..that was thebfirst thing I thought

[@izzy6301]

I wonder how many people saw the text poking fun at explosions and fire during the safety speech

[@anotheruser676]

I was thinking you must have the BIGGEST finger in the lab.

[@OMNI_INFINITY]

*Designed an HMD before and visiting china now and working on a new HMD design. Can supply some microlens arrays for the prototypes? Thanks in advance, if possible!*

[@smartereveryday]

This is better than reading a paper. Great work!

[@vexari_]

yes

[@applanateearth586]

What's a paper?

[@bumpyshow745]

@@applanateearth586 Before computers people made soup from trees and let it dry into sheets. After that they would use a mixture of chemichals to write stuff on. Basically a old kindle

[@AppliedScience]

I liked the whole journey! Maybe those laser crater spikes would make nice field emission sources. A big array could really pump out some electrons!

[@Muonium1]

That's exactly what I thought when I saw them too. It reminded me of the little picture that would invariably accompany all those "flat panel TVs could be just around the corner!" articles in the early 90s I would constantly see in Popular Science, Discover, etc.

[@dtroy15]

The production quality of this video was amazing. The backlighting, the 3d scans, everything. Bravo.

[@andymouse]

Dont mention this to Big Clive or we'll be getting more Ionizers.....cheers.

[@BreakingTaps]

Oh boy, I think you just nerd sniped me 😂 Now I'm elbow-deep in papers and patents about field emission displays and similar. Will see if I can wrangle something up with the tools I have! The other potential project I was thinking of was something like this "massively parallel AFM" paper (www.nature.com/articles/s41467-020-20612-3)

[@ThomasAndersonbsf]

@@BreakingTaps I was actually thinking if they were coated in aluminum like how thermal blankets are, these could be gathering points for phonons?(thermal equivalent to electrons and photons? not sure right now what the term is) but basically heat is absorbed easily by the unaluminized surface as IR radiation if you had say a vacuum behind it, but vacuum on the aluminized side would mean any thermal energy lost would be IR photons and these get rejected back into the vacuum so assisting very low amounts of thermal energy to collect enough in a centralized point to eject it as an IR photon, on the aluminized side could be what will make a true passive thermal diode where the thermal energy is also doing the work of moving itself from the cold side to the warm side. Just imagine a refrigeration unit that uses no power and you have an opening to let heat back in through micro pores to even it out, to regulate the temperature rather than generating loads of heat running compressors or the heat generated by running electrons through peltier units to cool something to add to the heat you have to manage, where the passive cooling system both costs no energy to run, just to build the unit, and does not have to regulate additional heat created powering it! (my idea using thermal blankets stacked with air gaps between each layer and all aluminized sides of the blankets facing the same direction to block heat from sunlight ect, during summer worked extremely effectively just with 3 layers, but like peltiers stacked I am guessing more layers would mean more efficiency, that and coupling it with using aerogel supports to spread the layers out so conduction of heat back into the chamber is minimized)

[@smartereveryday]

I wonder if you you were to tilt the specimen down just a bit before you spin it by placing it on a slight wedge. This may make the mold release to run "down" and flow out of the crater. Like this: ⦣ Angle of plate 🠒 Spin force Just an idea.

[@BreakingTaps]

Not a bad idea! Would be interesting to see how much (or if) it affects the layer thickness as well, or if there is any kind of gradient effect. One thing I neglected to mention in the video is that it's a race against solvent evaporation too... as the thin film spreads out, the solvent rapidly evaporates and the solids "crash out". Handy when you're trying to spin photoresist to a known thickness, less handy when trying to get an even coat of mold release :) Cheers for the idea! Will try it out next time I'm using the mold release again!

[@frollard]

@@BreakingTaps I wonder if it would be feasible to have a saturated atmosphere of solvent inside the spin coater to reduce evaporation giving a longer work time. Very cool vid top to bottom!

[@ThomasAndersonbsf]

@@BreakingTaps I am wondering if there is a surfactant that you could use that is a liquid at room temp so you can be sure when smon out it is a single layer of the surfactant molecules standing up off the surface of the mold either that does not bond to the resin or does but the surfactant easily lets go of the silicon. also on smoothing the surfact I wonder if a smaller molecule based material would work better like using graphite that is used for EDM machines :)

[@sakelaine2953]

6:34 it's a fundamental effect, the reason it's not in papers is because most of the people writing papers would take it for granted that their audience knows that catalysts just speed up a process that would happen by lowering the energy cost through mediation. So if you're in a situation where using a catalyst would help, remember that the desired effect is still happening at a slower rate. For most stuff this doesn't matter at all; at the scales you're working with it's important and I'm glad you figured it out.

[@johnathancorgan3994]

In Australian sheds, as long as you don't contaminate your working area with anything yellow, HF is fine to handle.

[@m1lkweed]

As all chemists know, yellow is evil

[@rickypoindexter9505]

@@m1lkweed would you mind explaining why? As a non chemist the only thing that comes to mind is yellowcake.

[@simonargus7662]

@@rickypoindexter9505 it's a meme from the the channel "Explosions&Fire", an australian guy that makes quite funny chemistry video about mostly explosive stuff

[@BCurt1776]

I like the shout out to Explosions & Fire lol. Great video!

[@MaterialsSci]

Hello! In your 'molding problems' section, you mention dimples near the top of your lenses. If indeed the problem is from an over-accumulation of mold release, you could try sputtering a thin film of gold onto the silicon surface and using that as a sort of mold release because the silicon will not stick well to the gold without a proper adhesion layer; additionally, the PDMS will not stick well to the gold without a specific chemical treatment (chemical treatment to make the gold adhere to the PDMS very well can be done really easily with a not very dangerous chemical called MPTMS). If the gold sputtering route does interest you, using the MPTMS surface treatment, you can make static mirror arrays as well as strain-tunable mirror arrays and strain-tunable plasmonic devices because of the metal first-surface on the PDMS.

[@BreakingTaps]

Oh! That's a really clever trick! Might give that a try and see how it goes, and definitely a useful tip for future work. MPTMS sounds _super_ interesting for plating PDMS, I didn't realize that was possible (at least robustly... I coated them with a thin layer of silver to help with SEM imaging but figured it would crack/delaminate quickly). That's really cool, will look into that more. Could make for some really interesting experiments in the future. Thanks!

[@MaterialsSci]

@@BreakingTaps The MPTMS route is really fascinating chemically speaking, the chemical has a sulfur group on one end that gives good bonding to gold and a silane group on the other which bonds well to the PDMS. Immersing the gold layer in a MPTMS solution is quick and easy too and that's all that you really need to do before spinning on your PDMS since the MPTMS forms a self assembled monolayer. I'd be happy to share my recipes if you'd like, could maybe save some time. Sputter coating PDMS directly with a metal is also interesting, the thickness of the metal film (at least in the case of gold) that you coat the PDMS with changes the final morphology of the film e.g., if the film is above a certain thickness range then you can end up getting a very wavy (buckled) surface which can be used for all sorts of stretchable electronic contacts and interconnects (for wearable electronics and things), as well as strain-tunable random gratings (these end up being also very interesting and strange to look at as they have an appearance that resembles silvery-white, rainbow-ish, diffractive gold)

[@jeremygalloway1348]

Uranium will work too...possibly

[@KallePihlajasaari]

What about a transparent layer so it does not affect the optical quality of the lens. Is TinOxide a possible mould release?

[@MaterialsSci]

@@KallePihlajasaari Having oxides on the surface in general is part of the sticking problem because PDMS bonds pretty well to oxides. Silicon itself will arrive with a SiO2 passivation layer for example. Since metals like Au have very weak bonding to un-modified PDMS, you can coat a surface like Si or a passivated surface like SiO2 and make a nonbonding interface that allows liftoff of the PDMS or other materials you may cast onto the surface. An oxide like SnO2 would probably stick pretty strongly to the PDMS since the PDMS itself is an Si-O polymer that bonds well to oxides and would likely not perform as well as Au or Ag for liftoff. Additionally, films of Au are pretty highly transparent (although transmitting greenish blue light) when grown in very thin films ~20 nm or less; having metals be partially transparent in thin films is sort of the basis of plasmonics and some metamaterial lenses

[@thomasesr]

You should shine a cheap laser pointer through the glass slide microlenses and project it on a wall to see if it does anything interesting.

[@kaysb80]

Anything can be handled in that one shed in Australia ;D

[@TheLtVoss]

If it turns yellow we might run in to problems

[@SeanLinsley]

this is awesome, feels like an Applied Science video

[@meetoptics]

The explanation is amazing!!!

[@abdomohamed-qt1he]

This is real research, not a traditional KZbin random trial. Loved it

[@pauls5745]

yes! generate so many of those peaks as close as possible and you'll see the material can be hydrophobic and other interesting properties

[@mikepeterson9733]

BT, you are one of the people who make KZbin an amazing place. Thank you so much for everything you show us!

[@HuygensOptics]

Very nice results Zach! I guess if you really dive a little deeper into the process, you could probably make much better lens arrays, maybe it is even possible to make well-defined aspherics. But then you need to be in control in every parameter of the process. Developing new technology into something useful is always a long and bumpy road.

[@BreakingTaps]

Thanks! Yeah, definitely a rabbit hole :) After sorting out the molding issues, would probably need to spend some time characterizing the ablation crater... it's likely not spherical at all, given the (theoretically) gaussian pulse profile. And a lot more work to make the system consistent/repeatable, no mechanical misalignments, etc. One reason I'm happy about youtube projects! I can get the idea working and then move on, skipping all the actual hard work! 😁

[@aetius31]

Btw, you could try using ammonium fluoride as an etchant instead of HF. It is much safer to work with and the fact it has a lower etching rate could remove the debris without eating too deep into the creaters. Also maybe going for an evaporation coating for the mold release agent could be better than spin coating, for instance just heat up gently a silicone oil with your slide just above the surface.

[@BreakingTaps]

Oh, will look into ammonium fluoride! That's basically what's in the glass etching creams right? Totally fine with slower rates as long as it's safer, and it'd probably be more controllable that way anyhow. Cheers for the tip (and the evap coating, will try that!)

[@aetius31]

@@BreakingTaps Glad you find the tip interesting! I heard that silicon fluoride kinda works aswell but i never tried it. Also for the mold release,you can try putting a few drops of silicone oil into toluene dipping your slide into it and let evaporate, I have not idea of the nedeed ratio of silicone tho.

[@izzieb]

The oblong micro lenses aren't bad - they're just anamorphic micro lenses.

[@xenontesla122]

Perfect for filming widescreen movies of tardigrades XD

[@BreakingTaps]

I think you both win the best-comment award :)

[@villebooks]

@@xenontesla122 watching this is on my bucket list x'D

[@DarqeDestroyer]

17:58 It's amazing how a tiny "micro spike" about a micron tall, totally looks like a giant geological feature, an enormous series of concentric rings with a giant mountain in the middle, like mount doom or something.

[@ChrisTuttle]

Ever since the first demonstration of light field photography, I have been trying to figure out how to make my own micro lens arrays. Your video covers so many aspects of whats involved that “finally” I think I understand the magnitude and scope of this task. This is an awesome video! Thanks! I am looking forward to your follow up videos regarding this project.

[@BreakingTaps]

Thanks for watching! There might be some easier methods which probably don't involve so many exotic chemicals or tools. I think the photoresist-slumping method is probably a bit easier (not sure the right keywords... basically pattern small circles of photoresist and then heat them up, causing the spots to soften and slump into hemispheres). Does require some kind of lithography technique though, and two rounds of molding to get the final shape. There might be even easier techniques, not sure, it definitely seems like a field where there are a lot of creative techniques :) Goodluck!

[@heidelbergaren5054]

@@BreakingTaps It’s called reflow, the technique to heat resist so it forms semi-spheres. But it also means that it’s only rotational symmetrical lenses that can be formed

[@98f5]

I too love and wish for light field cameras.

[@LanceThumping]

I've been thinking about light field photography too recently. I was wondering if the sensors could be made either as spires or in holes so that the angle could be detected without increasing the size of the sensor needed.

[@julians7268]

Videos can NEVER be too long. I'd have watched this for 5 hours just admiring the different structures that can be produced from laser etching.

[@fastindy]

10:21 "There's always a silver lining" I see what you did there

[@rocketman475]

The mold release buildup problem might be improved by - 1. Lowering its viscosity with a compatable solvent. 2. Spinning it with the apparatus upside down after applying mold release with a spray bottle from underneath. 3. Make sure the release agent is properly set in order to prevent it slumping into the hollow. So store it upside-down until certain that it has cured. ° Upside-down application might produce a thickening to occur around the outer rim of each micro bowl, and that might be able to be manipulated so as to result in a superior end product. Cheers. 👍

[@edgeeffect]

I love stuff like this... contrasting my own difficulties with achieving mm precision with you talking about sub micron structures is great. :)

[@julians7268]

That hexagonal pattern... that should be incorporated into merch or something. It looks freaking awesome. Loved the video.

[@BRUXXUS]

When I'm recommended a video from a (relatively) small channel that's FULL of comments from my absolute favorite channels I know I've found something special. :)

[@meetoptics]

The explanation is amazing!!!

[@BioBush]

Just watching you bounce through different problems and solutions and theories and observations is so interesting. I have zero background in this, but still want to see your future discoveries. Thanks for doing this work!

[@olpizl]

That „Explosions&Fire“ reference. Love it. Great video btw!

[@ThomasAndersonbsf]

those rough looking ridges look like a way to super micronize the thickness of a sound absorbing coating to go on a wall or something similar. might be a cool experiment to make enough to put a cone of silence around a mic so only what is directly in front of it is picked up, any side glancing sound waves get absorbed mostly and don't hit the mic?

[@Greenicegod]

The reason sound absorbing materials are big and thick is because sound waves are on the scale of centimeters to decimeters. Any obstruction smaller than the wavelength of the sound you want to absorb is no obstruction at all. The wave will just roll past it without noticing.

[@ThomasAndersonbsf]

@@Greenicegod question, how does such a long wave travel in air when gas particles are so small? LOL

[@florianf4257]

For me it was no surprise that the continuous silver layer worked like a mask. The selective metal etching requires (according to your description) the H2O2 (and afterwads HF) to get below the metal layer, so it should only work with metal structures with relative low width or porous metal structures. With a continuous silver film, there is just no way the etchant can reach the silicon and thus it acts as a mask (except on the edges).

[@BreakingTaps]

Somewhat surprisingly, it depends on thickness of the metal film. There are some papers (pubs.rsc.org/en/content/articlelanding/2015/ra/c5ra15745e/unauth) that show both effects depending on the thickness. With 40nm of gold, you mostly get edge effects like you mentioned... it edges just on the edges of the metal and you start to get a "curved" structure. But with 20nm of gold, there were enough nano-pinholes that the etchant could diffuse through the metal film and etch evently (and also caused a forest of "nanowires"). So I only deposited 15nm of silver onto my wafers hoping it'd be similar. Not sure why it didn't work to be honest, perhaps silver reacts differently? It does have oxidation states that Gold doesn't, so maybe that plays into it somehow. I would have expected to at least see the edge of the silver to etch some but really didn't, no matter which sample or test I looked at :(

[@florianf4257]

@@BreakingTaps The problem might be that you sputter your metal layer. Layers deposited by thermal evaporation or e-beam evaporation typically have larger grains and thus more pinholes. In our old Edwards 306 the gold films have grain sizes of 10-20 nm, so a 20nm-film wouldn't be continuous. But with sputtering, the metal has a much higher mobility on the surface and thus you will get a film with higher density (which is less favourable in this case). If you are interested in a relative easy way to create large areas with (more or less) regular patterning you should look into nanosphere lithography: depositing a monolayer of small polystyrene beads by adding a drop of water with the right concentration of particles (we sucessfully used particles down to 220nm). The surface charge of the beads should be same as the sample), deposit your metal, and remove the beads (which can be done with scoth tape). You can also use a even lower concentrations of beads with beads having an opposite surface charge as your substrate and get a metal film with random holes. But in this case, you have to remove the beads by solvents and ultrasonic cleaning.

[@BreakingTaps]

​@@florianf4257 Ahh, that seems like a very plausible explanation. I bet that's the issue! I might try again with a _very_ light coating (few nm) and see if there is noticeable different results. Will check out nanosphere litho, sounds interesting and pretty approachable! Thanks for the brainstorming and suggestions!

[@olleolsson7837]

Nothing to do with the episode, but I really appreciate the black end screen that goes on for a couple of seconds. It’s very calming. Great editing idea. 👍🏽

[@darkairieal]

Man this is just the coolest youtube channel.

[@Ornateluna]

lol that explosionsandfire call out

[@synapticaxon9303]

What parameters are you using to produce the "micro-spikes"? If you coat them with silver, I suspect they can be used as a reflective axicon lens (or "reflaxicon"). Then it would be interesting to use your ablation laser reflected off that, producing a Bessel-like beam, or perhaps an array of these beams. You said they are about one micron tall and have a radius of 200-400nm? I would hypothesize that you can produce more uniform ablation/etching using bessel-like beams because the waste material will not interfere as much, there will be fewer optical aberrations. Add a phase conjugate mirror to the mix and you've got something special. Very interesting, indeed.

[@BreakingTaps]

Added some details to the video description! Basically low power (6-10%), 40kHz, and a 63mm lens on my particular machine. That's an interesting idea about the axicons! Will mull it over, and might be able to do something fun with the etched ablation craters too if they are coated. Hmmm

[@michaelfoye1135]

@@BreakingTaps Please permit me to offer some unsolicited advice. Watching your video, it occurred to me that the problem you were having is not unlike the sort of problems many hobbyists have when trying to make molds of toys or small gadgets. If I interpreted your description of your molding process correctly, you simply poured the silicon into the available gap on the mold you wanted to use. This is not a bad way to make molds for jelly candies, sugar candies, and other similar edibles. You may have noticed that many of these candies have hollows in their shapes not at all dissimilar to the ones that you have in your lenses. Fortunately there are a number of possible solutions to this issue. I recommend that you take a look at the methods used in industry to make casts and molds for metal, plastic, and silicone. What I think will be most beneficial tfor your purposes is adding a sprue, runner, and a riser to your casting. I would also ad an exit sprue for excess material. You want to pour more material than you are using, have a slight rise from the pouring cup and sprue into a well that connects to a runner, then to a riser, then another riser which may or may not have a gate and into the casting and the exit sprue which should rise to the level of the pouring cup sprue so it can catch all the materials being displaced, and help to maintain the pressure on the mold surface. Insufficient pressure on mold surface is a very large part of the problem you are having with the lenses being deformed. The added material has to be trimmed, but you will most likely end up with a significantly better quality final product. I hope that you will find this helpful. Thank you for sharing your interesting work.

[@Changitojuanito]

This is seriously amazing. The ideas that change the world are made from this.

[@meetoptics]

It is so good, definitely!

[@johndooley1941]

Nice, I remember about 25 years ago some researchers in the UK made a micro lens sheet film but I think the lenses were a few millimetres in diameter and the optics were such on the lenses you could shine a projector onto the lens film and then view the sheet from any angle and see the flat image that was being projected without distortion from pretty much any angle, the lenses accommodated for any distortion. I don't remember if they mirrored the back of the sheet or whether it was all in the shape of the lenses

[@TheBauwssss]

Put the mold release on, spread it around the surface so it touches every part and then spin it off at really high RMP, but adhere the slide to the rotor of the spincoater, hold the apparatus upside down and then turn it on! This way the mold release should be able to completely evacuate those cavities, allowing you to cast the microlenses without that tiny dent on each lens 'ball' 😁

[@jeffpkamp]

way off-topic, but I spent two or three minutes looking for a cricket in my house, that was actually helping you with the ambiance for the audio on this video :)

[@sublucid]

Can you make super hydrophobic surfaces using the spikes (or some other laser-pattern)?

[@JustATempest]

I like how this channel went from a workshop channel to straight up microscopic science.

[@meetoptics]

It is so good, definitely!

[@HaloWolf102]

I love research papers in video format. This was an amazing video, thank you for making it.

[@meetoptics]

Agreed, so well explained

[@frankgarcia8378]

This silicon spikes are probably from the expansion of the silicon upon cooling after melting. I get (much larger) ones when I use an electron beam deposition system for evaporating silicon. Careful control of the laser parameters should allow you to create spikes with different geometries (size, height, etc.).

[@FilmFactry]

You got my SUBSCRIBE in less than 40 seconds. very clear and interesting presentation. Some youtubers drag things on so long.

[@meetoptics]

It is so good, definitely!

[@aetius31]

Great video (as usual), I found quite funny that you dont have acetic acid but have no problem getting HF :)

[@BreakingTaps]

Hehe yeah, it made me laugh as well. I was certain I had some... turns out it was citric not acetic 🙃

[@MisterIkkus]

I am fascinated by everything you put out. Thanks so much for your hard work and excellent videos.

[@BreakingTaps]

Thanks for watching! Really appreciate it :)

[@ThomasAndersonbsf]

I wonder if the mold release would be cleared if you were to stick the whole thing upside down affixing it to the center so you could spray upward on it then spin to get it to that super thin layering effect, the other aspect would be to run it at various spin rates so you could find the rate that leaves more instead of less to create dimples of sunk in mold release where the pits are at, and it becomes your smooth surface for the lenses to form?

[@davidk7544]

try ablation under vacuum. try adding pinhole separate physical layer in the same pattern behind your microlenses. glass workers i've worked with say it's safest to handle HF with bare wet hands - kept wet and rinsed while working. prevents the acid from hitting the skin directly and does a bit of dilution and prevents direct contact with skin. it's the HF permeating skin that leads to bone loss under the contact. (not seen this in action) want to collaborate? tell me how.

[@johnmorrell3187]

I just attended a talk by a guy (Greg Nielson) who's developed a technology where two photon absorption is used to make silicon (or silicon carbide) susceptible to etching. Two photon absorption is caused when photons at energies lower than are needed to excite electrons out of the valence bands can still cause electrons to be excited when two photons together are absorbed. Since this is only statistically possible when the intensity of light is very high, you can selectively etch a region controlled by the focal point of a laser source. The silicon is transparent to the laser and doesn't have much effect except at this focal point, which means you can etch out 3d paths with very precise geometry and ridiculously high aspect ratios of tunnels (like aspect ratios above 1000). It's like SLA printing in reverse. Pretty cool!

[@lynxshd]

could you get a better mold, by slowing down the laser strike to spread the dimples (adding more space between each dimple ) making more room for the dimple to growing during the longer etching period? that way you can capture a smoother full sphere. Cool way to make lemonade out of lemons.

[@das250250]

"Or maybe a shed in Australia" haha

[@YodaWhat]

@Breaking Taps - I suspect your laser etching was so intense, it vaporized the photoresist, causing *ablative etching* of the underlying material. With that in mind, I think you could skip some steps and the dangerous chemicals, by just painting the surface with something that is black at your laser wavelength, and directly etch your pits. You will of course have to experiment with thickness of the paint and the laser power/focus, but you should be able to produce etching of a wide range of surface textures just by varying those 2 parameters. I discovered this effect when etching patterns onto the back of mirror tiles. In that case, too little laser power would remove just the black paint, leaving the mirror metal largely undamaged, which was then very hard to remove with further laser etching.

[@Yuzuki017]

17 19 yes. the same can be found in machining... with scraped ways. fluid... or liquid dynamics. its an interesting topic.

[@SybrenSmith]

Love your channel man. Really great storytelling Keep up the good work.

[@bastilux]

Realy cool project. I didn´t knew about metal assisted etching myself and will try it in my research. For the etching process: In my experience laser structuring of a silicon surface with a thin film layer of gold leaves some regions in crystaline and some in an amorph phase. So actually what you suggested with the melting. This is proven by several methods like TEM lamella and leads to interesting results with anisotropic etching, as the amorph layer reacts completely different to an KOH/Isopropanol etchant.

[@Zolbat]

First time watcher here, its incredible what technology you use and how you showcase what it does. I wonder if you could use those reliable spikes in a circular pattern to create a lens

[@MikeyMobes]

thank you for the great in depth safety discussion. Good on you. A safe chemist on youtube is few and far between.

[@markos.5539]

Such a cool project cuz the models and visuals were stunning. Tbf, I had a bit hard time catching up but its really interesting nonetheless.

[@bashkillszombies]

Whoa that guy has a black whiteboard, and he writes on it with light colored markers! That looks so cool! Way easier on the eyes too! You're a genius bro, you should patent it and call it the Breaking Taps's patented 'Unwhite Board.'

[@BreakingTaps]

Hehe :)

[@devjock]

Could you try skipping the coating / molding process and ablate acylics directly? Like what they use to form lenses in Magneto-Optical media, like Minidisc's? With your setup, you might have a lot more control.

[@tedz2usa]

What if you used strong bursts of compressed air after spinning, to "blow" out the deposited mold release? So awesome to watch this journey!

[@TristramBudelcom]

You don’t have to use a mould release with making the pdms mould. When I used to work at the energy research center of The Netherlands I used to make things like this with PDMS at scale.

[@DerClaudius]

Interesting, thanks. I wonder if you could spin off the mold release by setting the glass plate on it's edge, off-center, etching facing out... you'd need another glass plate for balance and some holder for both plates.

[@haddow777]

Wondering. Do you think using some level of ultrasonics could help with the agent pooling in the dimples issue? Certain frequency vibrations can liquify sand, at least in function. It may be capable to the friction and viscosity of the liquid so it will flow more freely. Or maybe spin it upside down, so gravity works for you with the centrifical force. That way, any blobbung happens at the lowest point, which should be the surface outside the dimples. Better to have the outside of the lense marred rather than the middle. Also, for the weird bubbling. I heard from another lithography video that the laser frequency is super important. Each frequency can interact differently with different compounds. In their case, the frequency laser they had wouldn't work with certain materials. So, if they coated the surface with them, their laser would go clean through it and interact with the material underneath, which was the opposite of what they wanted. Now, I'm no expert by any means. Still, the bubbling looks like it may be the laser is going past the surface and heating the material underneath, which if done for long enough begins to melt the upper layer through heat transfer, which may be resulting in the upper layer melting a bit and acting like a bubble containing gases from the laser interaction. Now, again, I may only have a hint of an idea of what you were going after, but if you are wanting to have the laser interact with the surface material, you may need to find a laser with the correct frequency to fully interact with that material. Just something I heard in a video, not an expert here.

[@andymouse]

I can't get enough of this stuff !.....cheers.

[@BreakingTaps]

Thanks for watching! :)

[@meetoptics]

It is so good, definitely!

[@youtubasoarus]

I wonder if a concentrated stream of compressed air (top down to the center) could assist in shedding the mould release from the dimples when it's spun? hmmm

[@freedom_aint_free]

The "forest" of spikes couldn't be used as a negative mold for better e.g more round and smoother lenses?

[@Theminecraftian772]

Fantastic production quality!! These microlenses might be useful for increasing solar panel efficiency by refracting the different light colors out of sunlight. Maybe a series of differently sized holes will yield some interesting result as a micro-refractor in various laser scenarios. Great science!!

[@heidelbergaren5054]

The films with lenses to increase effectiveness of solar panels are not symmetrically round, they look more like bananas

[@Theminecraftian772]

@@heidelbergaren5054 That's awesome!! Sad that this method of lens generation won't work, but I had no idea they used bananas to make solar panels.

[@KidCorporate]

Not sure why this particular video got me to subscribe, but here I am.

[@KallePihlajasaari]

Not too long, we want part two. Please.

[@techninja42]

Should definitely make an animation of the crater spikes at different adjacent settings, they seem so repeatable it could be seamless to make as many as you need for the different frames.

[@livingod101]

I wonder if you can do the same for a knife edge for a crazy sharp knife that you can shave individual hair length wise.

[@zombieregime]

For what its worth, in animatronics we would use a silicone release that was paraffin wax and hexane(iirc). I had the thought of spinning that on a mold to see if the surface left from the wax would be smooth enough. But considering the size scales and some of the other chemical engineering in other posts about releasing silicone, yall are miles beyond my level of chemical understanding LOL Still, love the channel. Its awesome seeing someone beyond the 'this is a resistor' beginning level kind of stuff, but not talking like a retired academic using terms only people with doctorates would understand. Makes for a great intermediate 'next step' if you will in learning higher sciences. 😁👍

[@OMNI_INFINITY]

*Designed an HMD before and visiting china now and working on a new HMD design. Can supply some microlens arrays for the prototypes? Thanks in advance, if possible!*

[@IhsanMujdeci]

Bro, I don't know pretty much anything in this field but I love your work! Learning slowly through osmosis.

[@JathTech]

Try placing the mold on top of the epoxy resin so the mold release flows out to the edges of the craters rather than to the bottom.

[@seanbrinlee4752]

This is really good stuff, I love seeing the notifications for your new videos!

[@meetoptics]

The explanation is amazing!!!

[@charlesr3389]

Did you ever follow up with the nano spikes? It would be really cool to be able to replicate that effect and explore possible applications in metasurface fabrication.

[@abhishekkulhari]

Great video! All the etching talk takes me back to my IC Fabrication Class.

[@meetoptics]

The explanation is amazing!!!

[@tom7]

Very neat!

[@meetoptics]

Agreed, so well explained !

[@saddlepiggy]

I wonder if spikes like mentioned at the end could be used to make better ion engines?

[@benrogers5845]

Excellent video, thanks for sharing your work!

[@DavidLindes]

15:06 (and 15:39 makes it easier to see) - soooo much sensor dust! :'( ( ;) ) But seriously: fascinating, cool stuff. Thanks for sharing! And for skipping filming the deadly parts!! Safety takes priority.

[@SteelWolf13]

17:20 you can see his brain trying to check his mouth from saying corners when referring to a half sphere.

[@BreakingTaps]

😁

[@renatobugge6863]

Very nice presentation. The anisotropic Si etching you experience in the first part is probably due to the material quality or purity of your Si substrate. It could be residue from the polishing or it could be the actual material (when the ingot was made). If you want to repeat it, I would go for high resistance FZ Si with a good RCA cleaning procedure before you start. I like your warning about the HF. Its extremely dangerous. HNA etching is very fast and tend to show localized etching variations that would probably not give you any good result.

[@eirikolsnes]

Spin it upside down to avoid "puddles"?

[@imxheartz7846]

18:10 could you use that for gekko tape?

[@dieselphiend]

When YT can provide you with a better education than institutions.

[@georhodiumgeo9827]

Dude you got a comment from Applied Science and SmarterEveryDay. That's legendary stats right there. Great video, thanks. Also it was not too long, you could have rambled for another hour and I would have enjoyed the whole thing. Edit: you got Huygens Optics down there too! damn.

[@justsomedudeontheinternet]

would you be able to flip the thing over after spin coating for a while, and run it again? Or would that lose all the coating to gravity? Alternately, would an even pressure of an non-reactive gas during spin-coat help to smooth down the mold release lumps?

[@YaaMan42]

Could the high aspect etching be used to create a very large surface area per sqmm? Would be interesting to see if it would be viable as a heatsink. Like the inside of a heatpipe.

[@beautifulsmall]

geko fingers have microprofiled contours. many have tried, none im aware of have suceeded. I bought some stainless steel weld cleaner which contains HF and I ve watched a few vids but didnt know it doesnt burn. which i should have realised. which makes it organic not but eroding until it finds calcium. I think i will return it to the suppliers.

[@NerdSnipingBatman]

I wonder if instead of a subtractive manufacturing process, you could instead find some way to form micro bubbles out of clear resin with a specific radius and regular arrangement on an array pattern. I'm picturing something like a grid that you pre-form using a resin or sla printer, and then maybe dip the array into resin and allow the surface tension to naturally form perfect spheres in the grid. Maybe you could get more perfect micro lenses

[@holzmann8443]

Could compressed air be used to blow the extra release agent out of the lenses? Really cool stuff. What could a microlense array be used for?

[@jaytravis2487]

Wouldn't it be cool if we could predict coefficient of friction between surfaces as a function of the images you obtain? I couldn't begin to tell you exactly how to analyze,/characterize the individual surfaces. Forgive my ignorance if that's all been figured out already

[@dainius4168]

An extremely well made presentation!

[@FM-not-AM]

What became of this micro lens? Is it possible to adjust the size & shape of these lens dimples? Can a plate be reshaped for a lining of a larger lens or the inside surface of a sphere? Is the texture usable or too small? Maybe a micro sluice? Sound redirection? Fine Video, right was a smidgen long but I stuck it out.

[@kingofnothing2260]

If you can figure out how to make micro lenses inside lenses inside lenses without them touching, it should bend light to the next lens making invisibility cloak. Came up with this in 2006, but tech wasn't able to built this yet. - Steven McCament 2021

[@heidelbergaren5054]

With the same refractive index or with different refractive indices ? There’s also already meta materials that does this.

[@kingofnothing2260]

@@heidelbergaren5054 the angle of focus and so index would change by the size changes of each lens, but clarity shouldn't need to change

[@heidelbergaren5054]

@@kingofnothing2260 RF would change by the size of the lens - que ?

[@kingofnothing2260]

@@heidelbergaren5054 as long as the lenses are in the same physical size as the bandwidth desired to bend. They would focus light to the center, then reflect at a very shallow angle into the next set. The light may shift and may even be made conductive or polarized and the reflector could be the same or even a nantenna

[@wirehyperspace]

when i worked hydrofluoric acid we used wax for etching - and it is no joke had hole in glove and didn't know - a sware my heart was beating backwards - it felt like a Navy hot shot - in pain all night - platinum iron pyrite and lead makes sulfur but that isn't any real help like the silvadene cream for acid burns - robots are nice

[@Dovorans]

If you make a big array of those laser induced spikes, use that as a positive mold it would be cool to see if the a pad of silicone with a bunch of those spikes would act like the hairs on gecko feet.

[@janbeck8269]

Sweet! Thanks for sharing!

[@meetoptics]

It is so good, definitely!

[@albertsin3159]

It was easy and done in 198x. Germany made a device attached to SEM and create micro lens on Silicon waver.