Lighting Fires With Lemons

March 26, 2016 by Elliot Williams 64 Comments

We all know that you can stick copper and zinc in an acid and make a battery. And the classic demonstration of this is with a lemon. YouTuber [NorthSurvival] takes this to an extreme — starting a fire by shorting his lemon battery across some steel wool. (Video embedded below.)

Now calling this a “survival tip” is pushing it. A lot. When’s the last time you went camping with a bunch of zinc and copper nails, much less a supply of fresh lemons? It might be easier to put some matches in a waterproof canister, or just bring a lighter. But when the zombie apocalypse comes, and all the lighters are used up, the man with a lemon tree will be a millionaire.

Seriously, though, this demo made us question a few assumptions. First, when people do the potato- or lemon-battery experiment, they often use multiple lemons. Why? Hooking the pins up like [NorthSurvival] did in series seems like a no-brainer after the fact.

And the lemon seems to be putting out a fair amount of juice (Amperes, that is). We’ve got to wonder — what is the short-circuit current of a lemon battery? And why haven’t we seen specs anywhere? What kind of “science education” experiment is this anyway, without measurements?

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Home Made Farnsworth Fusor

March 26, 2016 by Richard Baguley 65 Comments

The Farnsworth Fusor is a fascinating device, a reactor that fuses hydrogen into helium by creating a plasma under a very high voltage. Although it isn’t a practical way to generate energy, it is a fascinating way to see nuclear fusion. An increasing number of home experimenters are starting to build their own fusors, and [Erik] decided he wanted to be among them. He’s put together a great build log of his progress, starting with a propane tank he bought off craigslist. He added a window, a vacuum pump and a 40KV power supply. Once he added some deuterium (electrolyzed from heavy water he bought from United Nuclear) it was ready to go. After a couple of failed runs, he got the characteristic plasma glow that shows that the reactor is working. The central globe is the plasma, while the light on the left side is a beam of electrons freed by the fusion process. So far, [Erik] has not detected the high-energy neutrons that would show that fusion is underway, but he is close.

Needless to say, this is not a casual build. [Erik] is using a 40KV power supply that would kill you in a heartbeat if your body happened to be the easiest pathway to ground, ~~especially as~~ the power supply ~~is generating~~ pulls over 9 amps to create the fusion reaction. [Erik] joins a select group of amateur fusor builders called the Plasma Club. It isn’t the first Farnsworth Fusor that we have covered, but it is one of the most impressive.

Moldy Rechargeable Batteries

March 24, 2016 by Al Williams 24 Comments

What’s worse than coming in from the workbench for a sandwich only to discover that the bread has molded? That red bread mold–Neurospora crassa–can transform manganese into a mineral composite that may improve rechargeable batteries, according to a recent paper in Current Biology.

Researchers used the carbonized fungal biomass-mineral composite in both lithium ion cells and supercapacitors. The same team earlier showed how fungi could stabilize toxic lead and uranium. Mold, of course, is a type of fungus that grows in multi-cellular filaments. Apparently, the fungal filaments that form are ideal for electrochemical use of manganese oxide. Early tests showed batteries using the new material had excellent stability and exceeded 90% capacity after 200 discharge cycles.

The team plans to continue the use of fungus in various metallurgical contexts, including recovering scarce metal elements. This is probably good news for [Kyle]. This is quite an organic contrast to the usual news about graphene batteries.

Image: Qianwei Li and Geoffrey Michael Gadd

Metal Magic: Heat Bluing Steel Clock Hands

March 23, 2016 by Dan Maloney 23 Comments

Metalwork of any kind is fascinating stuff to watch. When the metalwork in question is in service of the clockmaker’s art, the ballgame changes completely. Tiny screws and precision gears are created with benchtop lathes and milling machines, and techniques for treating metals border on alchemy – like heat-bluing of steel clock hands for a custom-built clock.

If you have even a passing interest in metalwork and haven’t followed [Clickspring]’s YouTube channel, you don’t know what you’re missing. [Chris] has been documenting a museum-quality open-body clock build, and the amount of metalworking skill on display is amazing. In his latest video, he covers how he heat-blues steel to achieve a wonderful contrast to the brass and steel workings. The process is simple in principle but difficult in practice – as steel is heated, a thin layer of oxides forms on the surface, enough to differentially refract the light and cause a color change. The higher the heat, the thicker the layer, and the bluer the color. [Chris] uses a custom-built tray filled with brass shavings to even out the heat of a propane torch, but even then it took several tries to get the color just right. As a bonus, [Chris] gives us a primer on heat-treating the steel hands – the boric acid and methylated spirits bath, propane torch flame job and oil bath quenching all seems like something out of a wizard’s workshop.

We’ve covered [Chris]’ build before, and we encourage everyone to tune in and watch what it means to be a craftsman. We only hope that when he finally finishes this clock he starts another project right away.

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Enzymes From The Deep – The Polymerase

March 22, 2016 by Nava Whiteford 46 Comments

Our bodies rely on DNA to function, it’s often described as “the secret of life”. A computer program that describes how to make a man. However inaccurate these analogies might be, DNA is fundamental to life. In order for organisms to grown and replicate they therefore need to copy their DNA.

dna-replication — DNA structure and replication

Since the discovery of its structure in 1953, the approximate method used to copy DNA has been obvious. The information in DNA is encoded in 4 nucleotides (which in their short form we call A,T,G, and C). These couple with each other in pairs, forming 2 complimentary strands that mirror each other. This structure naturally lends itself to replication. The two strands can dissociate (under heat we call this melting), and new strands form around each single stranded template.

However, this replication process can’t happen all by itself, it requires assistance. And it wasn’t until we discovered an enzyme called the DNA polymerase that we understood how this worked. In conjunction with other enzymes, double stranded DNA is unwound into 2 single strands which are replicated by the polymerase.

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Organic Chemistry Circuits Are Flexible And Work Wet

March 21, 2016 by Al Williams No comments

As circuits find their way into more and more real-world environments, the old standard circuitry isn’t always up to the task. It wasn’t that long ago that a computer needed special power, cooling, and a large room. Now those computers wouldn’t cut it for the top-of-the-line smartphone. However, most modern circuits don’t bend well and don’t like getting wet.

An international team of researchers is developing chemical-based circuitry that uses gold nanoparticles and electrically charged organic molecules to build circuit elements that behave like semiconductor diode junctions. It’s simple to make flexible circuits that don’t mind being wet using this chemical soup.

In an interview with IEEE Spectrum, the developers mentioned that other circuit elements similar to transistors and light sensors should be possible. The circuits aren’t perfect, however. The switching speed needs improvement. Also, while conventional circuits don’t like to get wet, these chemical circuits have difficulties if things get dry. Still, like all technology, things will probably improve over time.

This technology needs a good bit of engineering refinement before it is practical. If you need flexible photosensitive circuits in the near term, you might try here. Meanwhile, waterproof circuitry just needs the right kind of enclosure.

Photo Credit: UNIST/Nature Nanotechnology

Machine Shop Soaps Are Good, Clean Learning Fun

March 13, 2016 by Dan Maloney 31 Comments

At first glance, it’s easy to dismiss the creation of custom bath soaps as far outside the usual Hackaday subject matter, and we fully expect a torrent of “not a hack” derision in the comments. But to be able to build something from nothing, a hacker needs to be able to learn something from nothing, and there is plenty to learn from this hack.

On the face of it, [Gord] is just making kitschy custom bath soaps for branding and promotion. Cool soaps, to be sure, and the drop or two of motor oil and cutting fluid added to each batch give them a little machine shop flair. [Gord] experimented with different dyes and additives over multiple batches to come up with a soap that looked like machined aluminum; it turns out, though, that adding actual aluminum to a mixture containing lye is not a good idea. Inadvertent chemical reactions excepted, [Gord]’s soaps and custom wrappers came out great.

So where’s the hack? In stepping way outside his comfort zone of machining and metalwork, [Gord] exposed himself to new materials, new techniques, and new failure modes. He taught himself the basics of mold making and casting, how to deal with ultra-soft materials, the chemistry of the soap-making process, working out packaging and labeling issues, and how to deal with the problems that come from scaling up from prototype to production. It may have been “just soap”, but hacks favor the prepared mind.