Fail Of The Week: A Potentially Lethal Tattoo Removal Laser Power Supply

Caveat emptor is good advice in general, but in the wilds of eBay, being careful with what you buy could be life-saving. To wit, we present [Les Wright]’s teardown and very ginger power-up of an eBay tattoo-removal laser power supply.

Given that [Les] spent all of around $100 on this widowmaker, we’re pretty sure he knew what he was getting himself into. But he likely wasn’t quite prepared for the scale of the sketchiness this thing would exhibit. The deficiencies are almost too many to number, starting with the enclosure, which is not only made completely of plastic but assembled from individual sheets of flat plastic stock that show signs of being glued together by hand. Even the cooling water tank inside the case is pieced together this way, which probably led to the leaks that corroded the PCBs. Another assembly gem is the pair of screws the big energy storage capacitor is jammed under, presumably to hold it in place — because nothing says quality like a BOM that can’t spring for a couple of cable ties. Click through the break to read more and see the video.

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Laser Welding With A Tattoo Removal Gun

Dating as far back as the early 1960’s, researchers were zapping tattoo inks with laser light was an effective way to remove the markings from human skin. At the time it was prohibitively expensive. But the desire to have an undo-button for badge choices is strong, and thus the tattoo removal gun was born.

These days you can pick up one of these zappy, burn-y wonders for far less than a flagship cellphone put their high-power-output to alternative use. [Andrew] recently discovered that these devices can be readily repurposed into a laser welding tool with just a bit of work under the hood.

He first came across the technology via videos from [styropyro], whose work we’ve featured before. The tattoo removal gun features a YAG laser, which is pulsed to create a high power density. In initial testing, the pulses were too short and of too high intensity to effectively weld with; instead, the pulses simply cratered the metal.

After delving in further, [Andrew] discovered that by removing the Q-switch optical component, the pulses from the laser could be lengthened. This reduces the power density, and allows the tool to weld various materials even on its lower power settings. Success was found welding steel, titanium, and other materials, though attempts to weld copper and silver faced little success. Test pieces included razor blades and small screws, which could easily be welded with the tool. Results of the razor blade welding is spectacular, with a high-quality welding bead achieved by taping the laser to a CNC mill for precise movement.

It could prove to be a useful tool for those experimenting with complex projects involving bonding metals at very fine scales. If you’re pursuing something exotic yourself, we want to hear about it!

Tattoo-Removal Laser Brought Out Of Retirement For A Megawatt Of Fun

We’ve got to say that [Les Wright] has the most fun on the internet, at least in terms of megawatts per dollar. Just look at his new video where he turns a $30 eBay tattoo-removal laser into a benchtop beast.

The junk laser in question is a neodymium:YAG pulse laser that clearly has seen better days, both externally and internally. The original pistol-grip enclosure was essentially falling apart, but was superfluous to [Les]’ plans for the laser. Things were better inside the business end of the gun, at least in terms of having all the pieces in place, but the teardown still revealed issues. Chief among these was the gunk and grunge that had accumulated on the laser rod and the flash tube — [Les] blamed this on the previous owner’s use of tap water for cooling rather than deionized water. It was nothing a little elbow grease couldn’t take care of, though. Especially since the rest of the laser bits seemed in good shape, including the chromium:YAG Q-switch, which allows the lasing medium to build up a huge pulse of photons before releasing them in one gigantic pulse.

Cleaned up and with a few special modifications of his own, including a custom high-voltage power supply, [Les]’ laser was ready for tests. The results are impressive; peak optical power is just over a megawatt, which is enough power to have some real fun. We’ll be keen to see what he does with this laser — maybe blasting apart a CCD camera?

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How Tattoos Interact With The Immune System Could Have Impacts For Vaccines

Tattoos are an interesting technology. They’re a way of marking patterns and designs on the skin that can last for years or decades. All this, despite the fact that our skin sloughs off on a regular basis!

As it turns out, tattoos actually have a deep and complex interaction with our immune system, which hold some of the secrets regarding their longevity. New research has unveiled more insight into how the body responds when we get inked up.

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A guy's leg encased in a 3D printer showing a fresh printed tattoo

Do, Dare Or Don’t? Getting Inked By A 3D Printer

This unusual tattoo hack by [Emily The Engineer] is not for the weak of heart, but let’s be frank: we kind of know her for that. And she gives out a warning, albeit at a good 10 minutes in, to not do this at home. What she’s about to do takes creativity and tech obsession to the next level: to transform a 3D printer into a functional tattoo machine. Therefore, [Emily] ingeniously modified one of her standard 3D printers to operate two-dimensionally, swapped its plastic extruder for a tattoo gun, and, yes, even managed to persuade a willing participant to try it out.

The entire process can be seen in [Emily]’s video below, which humorously yet meticulously documents the journey from Sharpie test runs to actually inking skin. Aside from a lot of tongue-in-cheek trial and error, this project requires a sheer amount of problem-solving. [Emily] employs firmware edits to bypass safety checks, and clever hardware adaptations to ensure smooth transitions between strokes. One impressive upgrade is the emergency solenoid system, a literal panic button to stop the machine mid-tattoo in case of troubleā€”a critical addition for something with needles involved!

This hack sits on the edge of DIY body modification, raising eyebrows and technical questions alike. If you missed the warning and are now frantically searching for tattoo removal options, know we’ve covered some (but you might be rightfully scared of automating that, too, at this point). If you haven’t lifted a finger while reading this, just do the safe thing: watch [Emily]’s video, and tinker about the subsequent purposes this discovery creates for 3D printing or tattoo art.

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Homemade Raman Laser Is Shaken, Not Stirred

You wouldn’t think that shaking something in just the right way would be the recipe for creating laser light, but as [Les Wright] explains in his new video, that’s pretty much how his DIY Raman laser works.

Of course, “shaking” is probably a gross oversimplification of Raman scattering, which lies at the heart of this laser. [Les] spends the first half of the video explaining Raman scattering and stimulated Raman scattering. It’s an excellent treatment of the subject matter, but at the end of the day, when certain crystals and liquids are pumped with a high-intensity laser they’ll emit coherent, monochromatic light at a lower frequency than the pumping laser. By carefully selecting the gain medium and the pumping laser wavelength, Raman lasers can emit almost any wavelength.

Most gain media for Raman lasers are somewhat exotic, but luckily some easily available materials will work just fine too. [Les] chose the common solvent dimethylsulfoxide (DMSO) for his laser, which was made from a length of aluminum hex stock. Bored out, capped with quartz windows, and fitted with a port to fill it with DMSO, the laser — or more correctly, a resonator — is placed in the path of [Les]’ high-power tattoo removal laser. Laser light at 532 nm from the pumping laser passes through a focusing lens into the DMSO where the stimulated Raman scattering takes place, and 628 nm light comes out. [Les] measured the wavelengths with his Raspberry Pi spectrometer, and found that the emitted wavelength was exactly as predicted by the Raman spectrum of DMSO.

It’s always a treat to see one of [Les]’ videos pop up in our feed; he’s got the coolest toys, and he not only knows what to do with them, but how to explain what’s going on with the physics. It’s a rare treat to watch a video and come away feeling smarter than when you started.

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The inside of a Laser-Induced Breakdown Spectrometer

Spectrometer Detects Chemicals By Zapping Samples With A Laser Beam

Here at Hackaday, we love projects that result in useful lab equipment for a fraction of the cost of professional gear. [Lorenz], over at Advanced Tinkering, built his own instrument for Laser-Induced Breakdown Spectroscopy, or LIBS, and it’s quite an impressive device. LIBS is a technique for analyzing substances to find their chemical composition. Basically, the idea is to zap a sample with a powerful laser, then look at the little cloud of plasma that results and measure the wavelengths emitted by it.

A plot showing the spectrum of hematite
The spectrum of hematite (iron oxide), compared to that of pure iron

The laser [Lorenz] used is a Nd:YAG unit salvaged from a tattoo removal machine. After it fires a pulse, a photodiode detects the light and triggers a spectrometer, which consists of a diffraction grating, a few lenses and mirrors, and a linear CCD sensor. The grating splits the incoming lights into its constituent components, which fall onto the CCD and trigger its pixels. An STM32 Nucleo board reads out the results and sends them to a PC for further processing.

That processing bit turned out to be a full project on its own. [Lorenz] called upon [g3gg0], who software that simplifies the operation of the spectrometer. First, it helps with the instrument’s calibration. Point the detector at a well-known light source like a laser or a fluorescent lamp, then select the expected wavelengths on the resulting spectral plot. The software then automatically calculates the correct coefficients to map each pixel to a specific wavelength.

The software also contains a database of spectra corresponding to chemical elements: once you’ve taken a spectrum of an unknown sample, you can overlay these onto the resulting plot and try to find a match. The resulting system seems to work quite well. Samples of iron oxide and silver oxide gave a reasonable match to their constituent components.

We’ve seen other types of spectrometers before: if you simply want to characterize a light source, check out this Raspberry Pi-based model. If you’re interested in chemical analysis you might also want to look at this open-source Raman spectrometer.

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