Dr. Frosty Cryotube Rack

Are your Mr. Frosty™ cryopreservation racks always filled up in the -80 by inconsiderate labmates?  Can't justify to your PI to fork over ~$150 for more of them? Consider the PhD alternative to Mr. Frosty™: the Dr. Frosty™! This is the first open-source (to my knowledge) isopropanol based cryopreservation rack for standard Corning 1.5/2.0ml size cryovials. It should fit any ~0.5" diameter cryovial and holds 18 like the standard Mr. Frosty. I can't personally guarantee the -1 C/min cooling rate, but it holds a similar volume of isopropanol with similar dimensions. Cells appear viable at a similar rate to normal Mr. Frosty, but your mileage may vary depending on how sensitive your particular cell type is to cryo conditions. 

Recommended filament is PLA or possibly ABS (untested), PETG is NOT resistant to isopropanol. Print conditions are .2mm layer height and with wall count >3, which will help to seal the rack and bottom to make them hold the isopropanol. If you have issues with leaking, you might need to tune your extruder steps/extrusion multiplier/retraction which can leave holes in your model for fluid to work through. It might be possible to acetone smooth ABS/ASA to help make it hold fluid, unfortunately most sealing agents are not isopropanol resistant. 

Extrusion calibration might also fix any issues with the lid being too tight, though this can be fixed by scaling the top by ~0.5% in the x/y axis. 

All the model orientations are in the recommended orientation for printing, the rack will require supports on the outside rim only, would recommend using paint on supports to build plate only. Otherwise, autogenerated supports would make removal difficult between the tube holders.