Glass: Classic, But Mysterious

For a large part of human history, people made things from what they could find. Some stones make arrowheads. Others make sparks. Trees can turn into lumber. But the real power is when you can take those same materials and make them into something with very different properties. For example, plant fibers turning into cloth, or rocks giving up the metals inside. One of the oldest engineered materials is glass. You’d think as old as glass is (dating back at least 4,500 years), we’d understand all there is to know about it by now. According to an interesting post by [Jon Cartwright] writing in Physics World, we don’t. Not by a long shot.

According to [Jon] there are at least five “glassy mysteries” that we still don’t understand. Sure, it is easy to just melt sand, soda, and lime — something we’ve talked about before — but, in fact, many materials can turn glassy when cooled quickly from liquid to solid. The problem is, we don’t really understand why that happens. Continue reading “Glass: Classic, But Mysterious”

Stresses Revealed With A Polariscope

There are a lot of ways that stresses can show up, at least when discussing materials science. Cracks in concrete are a common enough example, but any catastrophic failure in a material is often attributable to some stress that couldn’t be withstood. If you’re interested in viewing those stresses before they result in damage to the underlying material, take a look at this DIY polariscope which can view internal stresses in glass and other clear objects.

The polariscope takes its name from the fact that it uses polarized light to view the internal structure of a transparent object such as glass. When the polarized light passes through glass in a certain way, the stresses show up as lighter areas thanks to the stressed glass bending the light back into view. This one is constructed with a polarizing filter placed in front of an LCD screen set to display a completely white image. When glass is placed between the screen and the filter no light is seen through the polariscope unless there are stresses in the glass. Even placing a force on an otherwise un-stressed glass tube can show this effect, and [Advanced Tinkering], this project’s creator, has several other creations which show this effect in striking detail.

The effect can also be observed as colored areas in other plastic materials as well. It’s an interesting tool which can help anyone who frequently works with glass, but it’s also interesting on its own to see clues left behind from the manufacturing process of various household items. We’ve seen some other investigative methods for determining how other household items are mass produced as well, like this project which breaks down the injection molding process.

Continue reading “Stresses Revealed With A Polariscope”

Squares of sample materials placed on the laser bed awaiting the sensing head

Smart Laser Cutter Ad-on Detects Material Optically

Come on now, admit it. You’ve done it. We’ve done it. You know — you were really sure that sheet of plastic stock you found lying around the hackerspace was acrylic right? You dialled in the settings, loaded the design, set the focus and pushed the little green ‘start’ button. Lots of black smoke, fire, and general badness ensued as you lunged for the red ‘stop’ button, before lifting the lid to work out how you’re going to clean this one up.

That was not acrylic. That was polycarbonate.

What you need is the latest gadget from MIT: SensiCut: A smart laser cutter system that detects different materials automatically.

The technique makes use of so-called ‘speckle imaging’ where a material illuminated by a laser will produce a unique pattern of reflected spots, or speckles into a camera. By training a deep neural model with a large set of samples, it was found possible to detect up to 30 types of material with 98% accuracy.

The pre-baked model runs on a Raspberry PI zero with an off-the-shelf camera all powered from a power bank. This allows the whole assembly to simply drop onto an existing laser cutter head, with no wiring needed.

Even if you’re a seasoned laser cutter user, with a well-controlled stock pile, the peace-of-mind this could give would definitely be worth the effort. A more detailed description and more videos may be found by reading the full paper. Here’s hoping they release the system as open source, one day in the not-to-distant future. If not, then, you know what to do :)

Continue reading “Smart Laser Cutter Ad-on Detects Material Optically”

Printing, Plating, And Baking Makes DIY Microlattices Possible

To be honest, we originally considered throwing [Zachary Tong]’s experiments with ultralight metallic microlattices into the “Fail of the Week” bucket. But after watching the video below for a second time, it’s just not fair to call this a fail, so maybe we’ll come up with a new category — “Qualified Success of the Week”, perhaps?

[Zachary]’s foray into the strange world of microlattices began when he happened upon a 2011 paper on the subject in Science. By using a special photocurable resin, the researchers were able to use light shining through a mask with fine holes to create a plastic lattice, which was then plated with nickel using the electroless process, similar to the first half of the electroless nickel immersion gold (ENIG) process used for PCBs. After removing the resin with a concentrated base solution, the resulting microlattice is strong, stiff, and incredibly light.

Lacking access to the advanced materials and methods originally used, [Zachary] did the best he could with what he had. An SLA printer with off-the-shelf resin was used to print the skeleton using the same algorithms used in the original paper. Those actually turned out pretty decent, but rather than electroless plating, he had to go with standard electroplating after a coat of graphite paint. The plated skeletons looked great — until he tried to dissolve the resin. When chemical approaches failed, into the oven went the plated prints. Sadly, it turns out that the polymers in the resin expand when heated, which blew the plating apart. A skeleton in PLA printed on an FDM printer fared little better; when heated to drive out the plastic, it became clear that the tortuous interior of the lattice didn’t plate very well.

From aerogels to graphene, we love these DIY explorations of new and exotic materials, so hats off to [Zachary] for giving it a try in the first place.

Continue reading “Printing, Plating, And Baking Makes DIY Microlattices Possible”

Making Aerogel, It’s Not For The Faint-Hearted

Aerogel — that mixture of air and silica — is one of those materials that seems like a miracle. It is almost not there since the material is 99% air. [NileRed] wanted to make his own and he documented his work in a recent video you can see below.

If you decide to replicate his result, be careful with the tetramethyl orthosilicate. Here’s what he says about it:

And the best part is, that when it’s in your eyes, it gets under the surface, and the particles are way too small to remove. For this reason, you could go permanently blind.

It can also mess up your lungs, so you probably need a vent hood to really work with this. It isn’t cheap, either. The other things you need are easier to handle: methanol, distilled water, and ammonia.

Continue reading “Making Aerogel, It’s Not For The Faint-Hearted”

Color-Tunable LEDs Open Up Possibilities Of Configurable Semiconductors

The invention of the blue LED was groundbreaking enough to warrant a Nobel prize. For the last decade, researchers have been trying to take the technology to the next level by controlling the color of emission while the device is in operation. In a new research paper, by the guys over Osaka University, Lehigh University, the University of Amsterdam and West Chester University have presented a GaN LEDs that can be tuned to emit different colors from the same substrate.

GaN or Gallium nitride is a wide band-gap semiconductor that has been employed in the manufacturing of FETs that are known to have higher power density due to its high thermal capacity while increasing efficiency. In the the case of the tunable LED, the key has been the doping with Europium for creating energy bands. When an electron jumps from a higher band to a lower band, it emits energy in the form of light and the wavelength or color depends on the gap of energy jumped as per Plank-Einstein equation.

By controlling the current density and duty cycle, the energy jumps can be controller thereby controlling the color being emitted. This is important since it opens up the possibility of control of LEDs post production. External controllers could be used with the same substrates i.e. same LEDs to make a lamp of different intensity as well as color without needing different doping for R,G and B emissions. The reduction in cost as well as size could be phenomenal and could pave the way for similar semiconductor research.

We have covered the details of the LED in the past along with some fundamentals on the control techniques. We are hoping for some high speed color accurate displays in the future that don’t break the bank on our next gaming build.

Thanks for the tip [Qes]

Who Knew Cut Grass Would Be So Tricky To Move!

Like all publications, here at Hackaday we are besieged by corporate public relations people touting press releases. So-and-so inc. have a new product, isn’t it exciting! But we know you, our readers, we know you like hacks, and with the best will in the world, the vast majority of such things have nothing of the hack about them. Just occasionally though a corporate offering does contain a hack, and today we have a fascinating one from Charm Industrial, who are doing their best to make hydrogen from biomass. They were finding cut grass to be an extremely difficult material to handle, and their account of how they managed to feed it from a hopper into their machinery makes for interesting reading.

You might expect grass to flow from a conical hopper like an ungainly liquid, but in fact it readily clogs and forms bridges, blocking the outlet. Changing the design of the hopper made little difference, so they tried an auger. The auger simply compressed the blockage harder, resulting in the counter-intuitive strategy of running the auger in reverse. But even that didn’t work, leaving the area round the auger clear but the rest of the grass as a solid clump. Rotating plows were tried with multiple different profiles followed, but finally they settled upon a vibrating bin activator. It’s a crash course in materials handling, and though the Hackaday bench is likely to avoid having to handle cut grass except when emptying the lawnmower, it’s still worth a look.

We may have done very little with handling cut grass, but we’ve certainly taken a look at creating it.