A line-art diagram of the microfluidic device. On the left, in red text, it says "Fibrillization trigger (CPB pH 5.0). There is a rectangular outline of the chip in grey, with a sideways trapezoid on the left side narrowing until it becomes an arrow on the right. At the right is an inset picture of the semi-transparent microfluidic chip and the text "Negative Pressure (Pultrusion)." Above the trapezoid is the green text "MaSp2 solution" and below is "LLPS trigger (CPB pH 7.0)" in purple. The green, purple, and red text correspond with inlets labeld 1, 2, and 3, respectively. Three regions along the arrow-like channel from left to right are labeled "LLPS region," "pH drop," and in a much longer final section "Fiber assembly region."

Synthetic Spider Silk

While spider silk proteins are something you can make in your garage, making useful drag line fibers has proved a daunting challenge. Now, a team of scientists from Japan and Hong Kong are closer to replicating artificial spider silk using microfluidics.

Based on how spiders spin their silk, the researchers designed a microfluidic device to replicate the chemical and physical gradients present in the spider. By varying the amount of shear and chemical triggers, they tuned the nanostructure of the fiber to recreate the “hierarchical nanoscale substructure, which is the hallmark of native silk self-assembly.”

We have to admit, keeping a small bank of these clear, rectangular devices on our desk seems like a lot less work than keeping an army of spiders fed and entertained to produce spider silk Hackaday swag. We shouldn’t expect to see a desktop microfluidic spider silk machine this year, but we’re getting closer and closer. While you wait, why not learn from spiders how to make better 3D prints?

If you’re interesting in making your own spider silk proteins, checkout how [Justin Atkin] and [The Thought Emporium] have done it with yeast. Want to make your spider farm spiders have stronger silk? Try augmenting it with carbon.

Flux, From Scratch

Soldering flux is (or at least, should be) one of the ubiquitous features of any electronics bench. It serves the purpose of excluding oxygen from a solder joint as it solidifies, and in most cases its base is derived from pine rosin. Most of us just buy flux, but [pileofstuff] is having a go at making his own.

He starts with a block of rosin and a couple of different solvents. Isopropanol we’re happy with, but perhaps using methanol for something to be vaporized within breathing distance isn’t something we’d do. At about 25% rosin to solvent ratio the result is a yellow liquid flux, which he tests against some commercial fluxes. The result is a reasonable liquid flux, something which perhaps shouldn’t be too much of a surprise, and is a handy piece of information to store away should we ever be MacGuyver-like stuck in a pine forest with a need to save the day with electronics.

It would be interesting to try the same technique but with a solvent selected to soften the rosin for a paste flux, and perhaps any chemists among our readership could enlighten us about just what rosin is beside the heavy fractions left after extracting the volatiles from pine resin.

In the past we’ve taken a close look at how solder really works.

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Nanotechnology In Ancient Rome? There Is Evidence

Anything related to nanotechnology feels fairly modern, doesn’t it? Although Richard Feynman planted the seeds of the idea in 1959, the word itself didn’t really get formed until the 70s or 80s, depending on who you ask. But there is evidence that nanotechnology could have existed as far back as the 4th century in ancient Rome.

That evidence lies in this, the Lycurgus cup. It’s an example of dichroic glass — that is, glass that takes on a different color depending on the light source. In this case, the opaque green of front lighting gives way to glowing red when light is shining through it. The mythology that explains the scene varies a bit, but the main character is King Lycurgus, king of Edoni in Thrace.

So how does it work? The glass contains extremely small quantities of colloidal gold and silver — nanoparticles of gold to produce the red, and silver particles to make the milky green. The composition of the Lycurgus cup was puzzling until the 1990s, when small pieces of the same type of glass were discovered in ancient Roman ruins and analyzed. The particles in the Lycurgus cup are thought to be the size of one thousandth of a grain of table salt — substantial enough to reflect light without blocking it.

The question is, how much did the Romans know about what they were doing? Did they really have the means to grind these particles into dust and purposely infuse them, or could this dichroic glass have been produced purely by accident? Be sure to check out the videos after the break that discuss this fascinating piece of drinkware.

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This Unique Flip-Flop Uses Chemistry And Lasers

One of the first logic circuits most of us learn about is the humble flip-flop. They’re easy enough to build with just a couple of NOR or NAND gates, and even building one up from discrete components isn’t too much of a chore. But building a flip-flop from chemicals and lasers is another thing entirely.

That’s the path [Markus Bindhammer] took for his photochromic molecular switch. We suspect this is less of an attempt at a practical optical logic component and more of a demonstration project, but either way, it’s pretty cool. Photochromism is the property by which molecules reversibly rearrange themselves and change color upon exposure to light, the most common example being glass that darkens automatically in the sun. This principle can be used to create an optical flip-flop, which [Markus] refers to as an “RS” type but we’re pretty sure he means “SR.”

The electronics for this are pretty simple, with two laser modules and their drivers, a power supply, and an Arduino to run everything. The optics are straightforward as well — a beam splitter that directs the beams from each laser onto the target, which is a glass cuvette filled with a clear epoxy resin mixed with a photochromic chemical. [Markus] chose spiropyran as the pigment, which when bathed in UV light undergoes an intramolecular carbon-oxygen bond breakage that turns it into the dark blue pigment merocyanine. Hitting the spot with a red laser or heating the cuvette causes the C-O bond to reform, fading the blue spot.

The video below shows the intensely blue dot spot developing under UV light and rapidly fading thanks to just the ambient temperature. To make the effect last longer, [Markus] cools the target with a spritz from a CO2 cartridge. We imagine other photochromic chemicals could also be employed here, as could some kind of photometric sensor to read the current state of the flip-flop. Even as it is, though, this is an interesting way to put chemistry and optics to work.

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DB Cooper Case Could Close Soon Thanks To Particle Evidence

It’s one of the strangest unsolved cases, and even though the FBI closed their investigation back in 2016, this may be the year it cracks wide open. On November 24, 1971, Dan Cooper, who would become known as DB Cooper due to a mistake by the media, skyjacked a Boeing 727 — Northwest Orient Airlines Flight 305 — headed from Portland to Seattle.

During the flight, mild-mannered Cooper coolly notified a flight attendant sitting behind him via neatly-handwritten note that he had a bomb in his briefcase. His demands were a sum of $200,000 (about $1.5 M today) and four parachutes once they got to Seattle. Upon landing, Cooper released the passengers and demanded that the plane be refueled and pointed toward Mexico City with him and most of the original crew aboard. But around 30 minutes into the flight, Cooper opened the plane’s aft staircase and vanished, parachuting into the night sky.

In the investigation that followed, the FBI recovered Cooper’s clip-on tie, tie clip, and two of the four parachutes. While it’s unclear why Cooper would have left the tie behind, it has become the biggest source of evidence for identifying him. New evidence shows that a previously unidentified particle on the tie has been identified as “titanium smeared with stainless steel”.

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How To Refrigerate With Urine

It’s often said that the best science experiments are the ones which do not require any special devices or ingredients, which makes the use of what naturally comes out of one’s body clearly one of the winners. It’s also the beginning of yet another [Hyperspace Pirate] chemistry video that’s both fascinating and unforgettable — this time introducing a considerable collection of urine, and the many uses of the urea in it, including its use for refrigeration.

The respective cooling effect of a variety of compounds in solution. (Credit: Hyperspace Pirate)
The respective cooling effect of a variety of compounds in solution. (Credit: Hyperspace Pirate)

As icky as this may sound, it doesn’t even rank in the top ten of quaint things people have historically done with urine, so extracting urea from it is rather benign. This is performed by adding sodium hydroxide to the starting component after heating, which creates gaseous ammonia (NH3) which was then condensed into its liquid (dissolved) form. In order to create the target compound – being ammonium nitrate – nitric acid (HNO3) had to be created first.

For this the older, but cheaper and easier Birkeland-Eyde process was used. This uses high-voltage electrical arcs to break down the nitrogen and oxygen in the air and cause the formation of nitric oxide (NO), that subsequently reacts with atmospheric oxygen to form nitrogen dioxide (NO2). Running the NO2 through water then creates the desired HNO3, which can be combined with the ammonia solution to create ammonium nitrate. The resulting solution was then evaporated into solid ammonium nitrate, to use it in an aluminium cooling cylinder, with freshly added water.

This is the simplest way to use the cooling effect of such solutions (pictured), but the benefit of ammonium nitrate over the original urea seems minimal. The low efficiency of this cooling approach means that the next use of urine will involve a much more efficient vapor-absorption cycle, which we’re sure everyone is squeezing their legs together for in anticipation.

We’ve been covering the refrigeration experiments [Hyperspace Pirate] has been conducting for some time now. If you’re into the science of making things cold check out how seashells can be turned into dry ice, or what goes into building a home cryocooler.

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Aqueous Battery Solves Lithium’s Problems

The demand for grid storage ramps up as more renewable energy sources comes online, but existing technology might not be up to the challenge. Lithium is the most popular option for battery storage right now, not just due to the physical properties of the batteries, but also because we’re manufacturing them at a massive scale already. Unfortunately they do have downsides, especially with performance in cold temperatures and a risk of fires, which has researchers looking for alternatives like aqueous batteries which mitigate these issues.

An aqueous battery uses a water-based electrolyte to move ions from one electrode to the other. Compared to lithium, which uses lithium salts for the electrolyte, this reduces energy density somewhat but improves safety since water is much less flammable. The one downside is that during overcharging or over-current situations, hydrogen gas can be produced by electrolysis of the water, which generally needs to be vented out of the battery. This doesn’t necessarily damage the battery but can cause other issues. To avoid this problem, researchers found that adding a manganese oxide to the battery and using palladium as a catalyst caused any hydrogen generated within the battery’s electrolyte to turn back into water and return to the electrolyte solution without issue.

Of course, these batteries likely won’t completely replace lithium ion batteries especially in things like EVs due to their lower energy density. It’s also not yet clear whether this technology, like others we’ve featured, will scale up enough to be used for large-scale applications either, but any solution that solves some of the problems of lithium, like the environmental cost or safety issues, while adding more storage to an increasingly renewable grid, is always welcome.