by Cathal Garvey, (C) 2009, colicensed under the GNU GPL v3 or later and the Creative Commons Attribution, Sharealike license v4 or later.
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- Dremelfuges for Purchase (as ornaments)
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This is a one-piece, 3D printable centrifuge rotor that can hold up to six eppendorf-style 1.5ml microcentrifuge tubes and spin them pretty damned fast. You can use it for laboratory operations like separating fluids, isolating free-floating cells, clarifying small volumes of liquid, emergency medicine, etcetera.
At least, you could do all of that hypothetically, if you were to actually use a Dremelfuge, which I don't endorse. I sell Dremelfuges as ornaments and memorabilia of the bad-old-days of 3D printing and DIYbio, and I caution that using Dremelfuges carries an eye-loss risk as well as whatever risks are inherited from spinning the fluids in question at high velocities.
In 2009, when I was starting to collect and buy equipment to build what would become my home-lab, I found there was a general need in the DIYbio community for an affordable centrifuge. There was also, of course, a general need globally of a cheap, easily-maintained and transport-friendly centrifuge for medical use in deprived or disaster-hit areas, something I was only peripherally aware of until researching the subject.
At that time I was still in honeymoon-period with my Makerbot Cupcake, one of the first consumer-end 3D printers ever and Makerbot Industries' first open-source printer (sadly, they have since ceased producing open source printers despite making their first $million selling products licensed openly and unpatented). It seemed natural to attempt 3D printing a rotor, which I could then attach to a rotary tool to make a centrifuge.
I realised after a quick inspection of the tools at hand that drills were generally not fast enough by far, built as they are to provide a balance of speed and torque. Dremels and other rotary multitools, on the other hand, commonly achieve rotary speeds of 30,000 RPM and are explicitly designed to tolerate forces against the axis of rotation; perfect for a centrifuge!
It took some time to design the first printable model. I worked in OpenSCAD, an excellent piece of Free/Libre modelling software that uses a C-like scripting language to "describe" components as aggregates and boolean products of fundamental types such as spheres, cylinders and cuboids. The disadvantage is slowness in the initial design, but the payoff comes later when the design becomes parameterisable, and where the precise layout of the design is mathematically guaranteed to conform to your needs. For something I was hoping to spin at 30,000 it was pretty much a requirement that there be no errors in balance or layout!
The initial designs were embarassingly buggy, attempting to minimise spokes and maximise tube capacity. On the sage advice of my father I moved instead to a six-spoke, six-tube arrangement which has stuck, and printed my first functioning rotors.
The first design, which went on sale as an ornament and even sold to two people (one of whom remains unidentified!) was still buggy, having as it did a poorly designed "seat" for the centrifuge tubes which would allow the tubes to eject at high speed above certain angular velocities! After observing the design of more conventional centrifuges I realised that the retaining force came not from gripping the sides of the tubes, as I was attempting, but rather from the 0.5mm "shelf" surrounding the lip of the tube, which sat at the mouth of the tube seats in conventional rotors. A quick redesign of the model in OpenSCAD, and I had Dremelfuge in its current form. It's been lurking quietly on Thingiverse and Shapeways ever since.
Since then, Dremelfuge has gone on to become a symbol for DIYbio overall, and has become an unexpectedly enduring talking-point for me. It's been featured in Nature, Makezine, and at least one book. It's been bought enough times from Shapeways to contribute a little bit to my other biotech products (though not overall that much), and it's been downloaded or printed by thousands (I have no firm way to know).
After these years of intervening work, Dremelfuge remains. My own lab is now closed for want of funding, my GM-license expired, and I'm at a crossroads career-wise. While assembling CVs and other documentation of jobseeking, I realised I'd never posted Dremelfuge to Github, so; here it is. I hope it's of use to you!
Don't use this. I used it for years, with little injury, but it's provided as an ornament only to others as it remains a highly risky way to centrifuge things. Unbalanced rotors may vibrate, move, lose control or eject tubes at high velocity. Spinning a rotor this large wears out Dremels somewhat fast. The best way to use this is to hang it on a tree and tell people about it.
Print dremelfuge in ABS only, NOT Polylactic Acid (PLA). Violent things have been observed to result from printing dremelfuges in PLA and, against my formal recommendation, spinning them. When printing, neither scrimp nor splurge on infill, but make sure the infill meets and fuses with the shell of the print to confer proper structural strength. An infill pattern that provides strong rigidity, such as hexagonal or cube infill, would be best.
Dremelfuge is designed to fit the cutting-disk holder of a standard Dremel 3000 series tool.
If you have a different cutting tool with varying dimensions, you can change some parameters
in the Dremelfuge V4.scad file and re-compile using OpenSCAD to
get a printable STL file.
Thanks to Kalani Kirk Hausman for letting me use his photograph of a dremelfuge to represent the device; my own camera skills are severely lacking!
Thanks to Catarina Mota for the shapes.scad library (included) which made it easier to design
Dremelfuge in the first place. I've met Catarina in person since (at TED Global), and she's awesome.
Thanks to my dad for going halves on a 3D printer in the first place, and for design input! :)
Thanks to my wife Niamh for years of patience with my biotech experimentation.