Inexpensive 3d Printed Microcentrifuge

I first got the idea to create a microcentrifuge when doing school labs, I found that the microcentrifuges we used were quite expensive ranging from the 110$ centrifuge our class has to other 500$ models. These centrifuges seemed quite simple and did not seem to have a very complicated design for how expensive they were. Since the samples that they spin are very small, I thought they would not require too large or expensive of a motor to operate.

I thought that there would be a cheaper way to make a centrifuge with simple components so I set out to make a simple microcentrifuge with readily available parts for under 10$.

(I am attending William Monroe Highschool in Virginia)

Some of the following components such as the switch and motor are easy to find in old toys. I obtained the switch, motor, and wire, all from old toys.

Supplies

• Toy DC Motor: here
• Switch: here
• PLA filament
• 9v battery
• Wire
• Tin foil (optional)
• 9v battery adapter (optional)
• Centrifuge .Stl files on step #4

Tools

• 3d printer
• Soldering iron
• Drill (if your pinter is really good you may not need one)

The rotor is the most complicated part to model because of its angled circular shape. To start making the rotor, I revolved a sketch and created a plane above the newly created form.

On that plane, I made two perpendicular lines with an intersection at the center of the rotor and created a "plane at angle" at a 45-degree angle on the line. I then created a -45-degree "plane at angle" on the same line and repeated it for the other line.

On each plane, I created a circle sketch and extruded it to cut the hole, and repeated it 3 times on all four planes to create the holes in the rotor.

To create the enclosure, I did simple extrudes to create a box and the switch hole. I then got the dimensions from this site for the motor enclosure and created several sketches to extrude.

The cover consists of several simple extrudes that leave enough tolerance for when the box is printed so it fits tightly. I also made a hole in the top for the spindle to poke through and a way to see the motor to observe any vibrations.

To make sure I was making the circuit correctly, I used tinkercad circuts to create a simulation of my finished circuit. I created the circuit by connecting the battery to the switch and then the motor. I created one version with two AA batteries and one version with a 9v battery. The one with two batteries had a rpm of 5900 and the one with a 9v battery had an rpm of over 17000.

For the end design, I decided to use the 9v circuit because it would save space in the box, and increase the speed and power of the centrifuge.

To print the parts I used pla with a .2mm layer height. I first soldered together the circuit shown above and printed a 9v battery holder since I did not have an adapter. I put tin foil in the battery holder and placed the wires so they contacted the tin foil which contacted the battery.

Next superglue the switch, battery, and motor down to the enclosure and place the lid on top. If the rotor does not fit onto the motor spindle, use a 1/16-inch drill bit to enlarge the hole slightly until it fits properly. There is no real need to superglue the rotor since it is not pressured to go up when spinning.

Below are both the .step files and .stl files I used for this project.

To operate the centrifuge, place the rotor on the motor spindle and place test tubes so they are balanced. This means if you have two tubes, they need to be placed opposite from each other and have the same weight to prevent vibrations. Because in my tests, I only had one tube, I had to use a piece of crayon as a counterbalance to prevent the vibrations.

After balancing the rotor flick the switch to start the centrifuge. Most lab experiments will have a time listed for the sample to be spun but most samples can be observed as well to see if the layers are emerging.

Before starting these tests, I want to say that they are not very scientific or completely reflective of lab use, it is just the best I can do during the summer without equipment. For some of the spins, I had to use part of a crayon to counterbalance the tube because I could not get another tube.

My first test of the centrifuge was to see if it could perform the basic laboratory practice of condensing a sample to conserve as much as possible. The purpose of this is to allow the fluid to be drawn by a pipette more easily and without wasting any sample.

To test this ability, I placed water drops in a centrifuge tube and spun the tube for 20 seconds. The result was the water being condensed in the bottom of the tube. This shows that the centrifuge is capable of condensing samples.

For the second test, I wanted to see if the centrifuge could separate out different layers of a somewhat homologous substance. For this, I used orange juice and spun the sample for one minute. There was a bottom layer that separated from the watery top substance that may have consisted of sugar and larger particles of pulp. This shows that the centrifuge is capable of separating some substances with components of different masses.

Overall, the centrifuge seemed to perform quite well as a simple tool for basic experiments and laboratory practices.

The other aspect of this project was the price so the breakdown of materials is as follows:

motor: $0.50

switch: $1.00

wire $0.50

PLA filament: $4.00

Solder: $1.00

Total: $7.00

There are some tools that are more expensive but most are already very accessible, such as a 3d printer at a local library.

This means that the centrifuge meets the price goal of under $10 and it is significantly cheaper than all common laboratory micro centrifuges.

The future of this project may include making it more stable with rubber feet or adding a lid to enclose the rotor while it spins. Speed control with a potentiometer could also make this project more helpful, even though most commercial models do not have one.

My hope is that with designs like this, scientific pursuits can become more accessible and simple for more people.

I hope you enjoyed this Instructible and if you have any questions, please let me know in the comments.