Making Microfluidics Simpler With Shrinky Dinks

It’s as if the go-to analogy these days for anything technical is, “It’s like a series of tubes.” Explanations thus based work better for some things than others, and even when the comparison is apt from a physics standpoint it often breaks down in the details. With microfluidics, the analogy is perfect because it literally is a series of tubes, which properly arranged and filled with liquids or gasses can perform some of the same control functions that electronics can, and some that it can’t.

But exploring microfluidics can be tough, what with the need to machine tiny passages for fluids to flow. Luckily, [Justin] has turned the process into child’s play with these microfluidic elements made from Shrinky Dinks. For those unfamiliar with this product, which was advertised incessantly on Saturday morning cartoon shows, Shrinky Dinks are just sheets of polystyrene film that can be decorated with markers. When placed in a low oven, the film shrinks about three times in length and width while expanding to about nine times its pre-shrunk thickness. [Justin] capitalized on this by CNC machining fine grooves into the film which become deeper after shrinking. Microfluidics circuits can be built up from multiple layers. The video below shows a mixer and a simple cell sorter, as well as a Tesla valve, which is a little like a diode.

We find [Justin]’s Shrinky Dink microfluidics intriguing and can’t wait to see what kind of useful devices he comes up with. He’s got a lot going on, though, from spider-powered beer to desktop radio telescopes. And we wonder how this technique might help with his CNC-machined microstrip bandpass filters.

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A Year-Long Experiment In OLED Burn-In

If you need to add a small display to your project, you’re not going to do much better than a tiny OLED display. These tiny display are black and white, usually found in resolutions of 128×64 or some other divisible-by-two value, they’re driven over I2C, the libraries are readily available, and they’re cheap. You can’t do much better for displaying a few numbers and text than an I2C OLED. There’s a problem, though: OLEDs burn out, or burn in, depending on how you define it. What’s the lifetime of these OLEDs? That’s exactly what [Electronics In Focus] is testing (YouTube, in Russian, so click the closed captioning button).

The experimental setup for this is eleven OLED displays with 128×64 pixels with an SSD1306 controller, all driven by an STM32 over I2C. Everything’s on a breadboard, and the actual display is sixteen blocks, each lit one after another with a one-second display in between. This is to test gradually increasing levels of burnout, and from a surface-level analysis, this is a pretty good way to see if OLED pixels burn out.

After 378 days of testing, this test was stopped after there were no failed displays. This comes with a caveat: after a year of endurance testing, there were a few burnt out pixels. correlating with how often these pixels were on. The solution to this problem would be to occasionally ‘jiggle’ the displayed text around the screen, turn the display off when no one is looking at it, or alternatively write a screen saver for OLEDs. That last bit has already been done, and here are the flying toasters to prove it. This is an interesting experiment, and although that weird project you’re working on probably won’t ping an OLED for a year of continuous operation, it’s still something to think about. Video below.

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Making a Flying Wing With Expanding Foam

Many radio control aircraft modelers will be familiar with the process of cutting wings out of foam with the hot wire method. The tools are simple enough to build at home, and it’s an easy way of producing a lightweight set of wings without too much hassle. [IkyAlvin] walks a different path, however (YouTube link, embedded below).

Expanding foam is the key here – that wonderful sticky material in a can that never quite goes where you want it to. MDF and foam is used to create a mold to produce the wing forms. It’s then a simple matter of loading floor underlay into the mold to act as the outer skin, and then filling the mold with expanding foam and waiting for it to cure.

The final parts are assembled into a flying wing, and the first test flight is remarkably successful. Using foam overlay as a skin also has the added benefit of providing a sleek silver finish to the aircraft. It goes to show that there’s always room to explore alternative techniques outside of the mainstream. If you’d like to get more familiar with the classic hot wire technique, though, we can help there too. Video after the break.

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Pocket Watch Becomes Pinhole Camera

A pinhole camera is essentially the combination of the camera obscura with photographic film. The pinhole acts as the lens, focusing the scene onto the film, and after exposure, the film can then be developed and you’ve got your picture. They’re a fun way to learn about photography, and easy to make, too. [Brooklyntonia] decided to undertake just such a build, secreted away inside a pocket watch.

The build starts with with the disassembly of the watch, which acts as the main cavity of the camera. A bellows is then constructed from leather and a toilet paper roll to allow the camera to still fold up inside the original watch case. A pinhole is then installed at the end of the bellows, and a plug is used as a shutter to allow the bellows to be properly unfolded prior to exposure.

It’s a fun build, and one that comes complete with instructions for the proper processing of film in your own darkroom – or bathroom. Pinhole cameras can be useful tools, too – particularly for things such as capturing an eclipse.

Making Crampons Out of Scrap

If you’re living somewhere that gets icy in the wintertime, you know the sidewalk can be perilous. Slipping on ice hurts like hell if you’re lucky, and can cause serious injuries if you’re not. Naturally, if you’re trying to get down to the hackerspace when it’s cold out, you’ll look for solutions. [masterbuilder] wanted to be surefooted in the coming season, and decided to build a set of crampons.

Scrap inner tubes are the key here, providing a source of hardy rubber for the build. The tubes are cut into a series of bands which are woven together in a hexagonal pattern. Steel nuts are included at various points to help grip the ice in inclement conditions. A larger strip of rubber is then used to form a band which secures the entire assembly to the wearer’s shoes.

It’s a design that’s intended for ease of use over outright performance. The crampons can be quickly attached and removed, and using nuts instead of spikes reduces the chance of damaging the floor if you forget to take them off immediately when returning home. If you’ve got any handy winter hacks of your own, you know where to send ’em.

Circular Linear Motor Becomes A Micro Motor Raceway

Over on Hackaday.io we have a lot of people playing around with the possibilities presented by cheap printed circuit boards. Whether that means making a quadcopter from fiberglass or a speaker from etched copper, we’ve seen just about everything. Now, finally, we have a miniature magnetic racetrack. It’s an ant highway, or a linear motor wrapped around into a circle. Or a tiny-scale model railroad. Either way it’s very, very cool.

The ant highway comes from [bobricius], one of the many makers tinkering around with coils and traces. This time he’s built a ten centimeter square board that is, effectively, a linear motor. It’s a three-phase motor made out of PCB coils, with a small magnetic ‘car’ that’s pushed forward. These coils are controlled by an ATtiny10 and a trio of MOSFETs. Wrap that linear motor into a circle and you have a neat little circular track that’s the smallest model car raceway you’ve ever seen.

As with all of [bobricius]’ circuit boards, this one demands a video, and that’s available below. This is an interesting bit of technology, and it’s more than just a raceway for tiny magnetic cars. This could be the beginnings of an analog clock with a digital heart, or the start of the smallest model train layout you’ve ever seen. There’s impressive work being done with PCB motors now that printed circuit boards are so cheap, and we can’t wait to see what’s next.

A quick Hackaday search will reveal [bobricius] as a prolific source of projects whose work we’ve featured multiple times. Favorites include a brushless PCB motor, and an FR4 cell phone.

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Analysing National Budgets With File System Tools

Understanding a national budget can be difficult, with political interests and distorted talking points obscuring the truth. There’s no substitute for diving into the hard data yourself, but it can be difficult to know where to start. [D. Scott Williamson] wanted to do just that, and took an unconventional path – using file system tools to analyse the 2019 US budget.

The basic idea is simple. A file is created for every line item on the budget, and this file is filled with a $ for every million dollars that item costs. These files are sorted into folders for the relevant bureaus and agencies responsible, creating a Fiscal File System representation of the entire budget. The file system can then be analysed with standard tools to get a look at the overall make up of the budget – in this case, WinDirStat does a particularly good job.

It’s a novel way to go about budget analysis, and fills a gap in the market now that Time Plots aren’t producing their Death and Taxes infographics anymore. Pre-cooked file systems covering budgets back to 1977 are available for your perusal, should you need to investigate how things have changed over time.

Unsurprisingly, we haven’t covered the national budget before, but we’re always down to talk file systems.