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 trouble—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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How The Main Frame Became The Mainframe: An Etymological Dissertation

In his most recent article, [Ken Shirriff] takes a break from putting ASICs under a microscope, and instead does the same in a proverbial manner with the word ‘mainframe’. Although these days the word ‘mainframe’ brings to mind a lumbering behemoth of a system that probably handles things like finances and other business things, but originally the ‘main frame’ was just one of many ‘frames’. Which brings us to the early computer systems.

We have all seen the photos of early computer systems, which not only filled rooms, but which also tended to consist of multiple units. This was something which the designers of the IBM 701 computer seem to have come up with, to make it possible to transport and install computer systems without cranes and the breaking out of walls. Within the IBM 701 system’s internal documentation, the unit containing the core logic was referred to as the ‘main frame’, alongside the ‘power frame’, the ‘core frame’, etc.

From this [Ken] then traces how the word ‘main frame’ got reused over the years, eventually making it outside of the IBM world, with a 1978 Radio Electronics magazine defining the ‘mainframe’ as the enclosure for the computer, separating it seemingly from peripherals. This definition seems to have stuck, with BYTE and other magazines using this definition.

By the 1960s the two words ‘main frame’ had already seen itself hyphenated and smushed together into a singular word  before the 1980s redefined it as ‘a large computer’. Naturally marketing at IBM and elsewhere leaned into the word ‘mainframe’ as a token of power and reliability, as well as a way to distinguish it from the dinky little computers that people had at home or on their office desk.

Truly, after three-quarters of a century, the word ‘mainframe’ has become a reflection of computing history itself.

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Hackaday Links: February 2, 2025

All things considered, it was a very bad week for aviation here in the United States. Three separate crashes, two of which involved US military aircraft, have left over 70 people dead. We’ll spare you the details since there are plenty of other places to get news like that, but we did want to touch on one bright spot in this week’s aviation news: the first successful supersonic flight by a US-made civilian aircraft. There are a lot of caveats to that claim, but it’s clear that Boom Supersonic is on a path to commercializing supersonic air transportation for the first time since the Concorde was retired. Their XB-1 “Baby Boom” test aircraft managed three separate supersonic runs during the January 28 test flight over the Mojave test range. As usual, Scott Manley has excellent coverage of the test flight, including a look at how Boom used a Starlink terminal and an iPhone to stream cockpit video.

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Is Fire Conductive Enough To Power A Lamp?

Is fire conductive? As ridiculous that may sound at first glance, from a physics perspective the rapid oxidation process we call ‘fire’ produces a lot of substances that can reduce the electrical insulating (dielectric) properties of air. Is this change enough to allow for significant current to pass? To test this, [The Action Lab] on YouTube ran some experiments after being called out on this apparent fact in the comments to an earlier video.

Ultimately what you need to make ‘fire’ conductive is to have an appreciable amount of plasma to reduce the dielectric constant, which means that you cannot just use any rapid oxidation process. In the demonstration with lights and what appears to be a (relatively clean-burning) butane torch, the current conducted is not enough to light up an incandescent or LED light bulb, but can light up a 5 mm LED. When using his arm as a de-facto sensor, it does not conduct enough current to be noticeable.

The more interesting experiment here demonstrates the difference in dielectric breakdown of air at different temperatures. As the dielectric constant for hot air is much lower than for room temperature air, even a clean burning torch is enough to register on a multimeter. Ultimately this seems to be the biggest hazard with fire around exposed (HV) electrical systems, as the ionic density of most types of fire just isn’t high enough.

To reliably strike a conductive plasma arc, you’d need something like explosive (copper) wire and a few thousand joules to pump through it.

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Giving A Proprietary Power Supply The Boot

You’ve probably noticed that everywhere you go — the doctor’s office, hotels, or retail shops, there are tiny PCs everywhere. These small PCs often show up on the surplus market for a very good price, but they aren’t quite full-blown PCs. They usually have little option for expansion and are made to be cheap and small. That means many of them have custom and anemic power supplies. We aren’t sure if [bm_00] needed a regular power supply to handle a graphics card or if the original power supply died, but either way, the HP small-form-factor box needed a new power supply. It took some clever work to be able to use a normal power supply in the little box.

At first, we thought this wouldn’t be much of a story. The motherboard surely took all the regular pins, so it would just be a matter of making an adapter, right? Apparently not. The computers run totally on 12V and the motherboard handles things like turning the computer on and off. The computer also was trying to run the power supply’s fan which needed some work arounds.

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Wearables queen [Becky Stern] with a microcontroller and a speaker. And a skull!

Wearable Tech Tips Directly From The Queen

What’s the only thing cooler than building something electronic? That’s right — wearing it proudly for all to see.

But maybe you’re not into wearables. Maybe it’s because you’re afraid of sewing, or simply scared that you won’t be able to launder that blinkenshirt you’ve always wanted to make. Well, the undisputed queen of wearables — [Becky Stern] — has a bunch of beginner tips for making DIY wearables. She’s created dozens and dozens of wearable projects and matching tutorials over the years and has graced these pages many times.

As [Becky] points out, once you have your idea sorted, the next thing you need is the tools to get the skills to do the parts you don’t know how to do yet. Even if that’s almost all of it, then this is the guide for you. Importantly, [Becky] reminds us that we should only bite off what we can chew, and that ready-made modules and such are perfectly fine.

There are some tips here that may surprise you. For instance, [Becky] recommends against conductive thread for beginners who already know how to sew by hand, largely because of power delivery and other issues. She also is somewhat anti-lithium battery pouch, preferring instead to use a couple of AAs or a USB battery bank for the renewability aspect.

Be sure to check out the video after the break, which has these tips and more.
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Custom Smartwatch Makes Diabetes Monitoring Easier For Kids

Living with Type 1 diabetes is a numbers game. There’s not a moment in the day free from the burden of tracking your blood glucose concentration, making “What’s your number?” a constant question. Technology can make that question easier to ask and answer, but for T1D patients, especially the kids who the disease so often impacts, all that tech can be a distraction.

To solve that problem for his son, [Andrew Childs] built this custom T1D smartwatch. An Apple Watch, which integrates easily into the Dexcom CGM ecosystem, seems an obvious solution, but as [Andrew] points out, strapping something like that on a nine-year-old boy’s wrist is a recipe for disaster. After toying with some prototypes and working out the considerable difficulties of getting a stable BLE connection — the device needs to connect to his son’s iPhone to get CGM data — [Andrew] started work on the physical design.

The watch uses an ESP32-S3 on a custom PCB, as well as a 1.69″ TFT IPS display and a LiPo battery. The board also has an accelerometer for activity monitoring and a vibrator for haptic feedback. Getting all that into a case was no mean feat, especially since some degree of water resistance and shockproofing would be needed for the watch to survive. [Andrew] had a case made by a local 3D printing company, and he managed to source custom-cut and silkscreened glass for the face. The result is remarkably professional-looking, especially for a software developer who hadn’t really stretched his maker wings much before tackling this project.

[Andrew] doesn’t appear to have made build files available yet, although he does say he intends to open-source the project at some point. We look forward to that as it’ll be a big help to anyone trying to hack diabetes care. Until then, if you need a primer on continuous glucose monitoring, we’re happy to oblige.