Modular Microcentrifuge Tube Ice Rack System

thingiverse

Everyone in molecular biology uses an ice bucket to chill their samples during routine procedures like PCR. If your lab is well funded you might even have a fancy ice rack that sells for upwards of $80 and keeps your samples in stable contact with ice/water. For those on a shoe-string budget like myself, a cheap and simple alternative was needed. Enter the Modular Microcentrifuge Ice Rack System. The system is very simple. All it requires is a print of the lid, water, and a styrofoam cup. I use a shallow Dart cup that came with some mexican take-out. It measures approx 4" wide at the mouth, 2" tall, and tapers to a base of about 3". This lid holds 9 1.5mL microcentrifuge tubes but I will be making more lids that cater to a wider range of tubes including the 50mL, 15mL, and even 0.2mL PCR tubes. Now for the dorky part: Data! After freezing about 250mL of tap water in the system for 3 hours, I did a triple repeat of an experiment that measured the rate at which 1mL of distilled water cooled from room temp to a steady state. I used a VWR Multi-Thermometer that is NIST traceable for the measurements and wrote down the temp every minute for ten minutes. The thermometer was allowed to sit in the sample at room temperature for one minute prior to insertion into the system and taking the initial reading. I included a picture of the graphed data for your viewing pleasure. The systems works great and cools to the required 2-6C in about 4 minutes and can hold the temperature for at least 1 hour. I would recommend a longer time in the freezer prior to use to ensure complete ice formation. The lid itself is designed to fit snugly onto the cup lip and may require a little wiggling to get it on. Any 4" mouthed cup will do. I designed the lid so that the tubes never make contact with the water so there is no condensation or chance of contamination due to water ingress. Enjoy! This thing was made with Tinkercad. Edit it online https://tinkercad.com/things/aTg7Ih3LweC Instructions Print desired lid. Find a styrofoam cup with a 4" mouth. Fill the cup to the top with cold tap water. (Ensure that you fill it as much as possible) Pop the lid onto the cup. Some water will spill out. You want this to happen as it ensure that as much of the tube shafts are completely submerged. Place rack system in the freezer for a few hours or until needed. Enjoy a chilled sample without heavy condensation and watery mess. NOTE Check the tips of the tube shaft for holes one printed. The thickness of the shafts are only 1mm so some printers may leave small gaps. If you do find gaps just dab a little super glue or smooth it out with acetone (nail polish remover). Also please excuse my printed example's appearance. My printer (Up! Mini which I love so very much) was silly with its calibration and squashed one end of the raft to the point where it fused. It otherwise prints clean in 4 hours using 38.4g of ABS with solid fill and 0.2mm resolution. Check on this thing from time to time as I will be adding more lids soon. Please leave a comment for any lid design requests or feel free to edit the thing directly using tinkercad.