The need for an economical centrifuge in day to day testing and in immediate crime scene investigation is on the rise. The overwhelming cost of a laboratory grade centrifuge prohibits use to high tech labs with enough funding to buy these machines. In this Instructable you will learn how to recycle a Dremel and some other parts to create a Dremel powered centrifuge spinning at 30,000 RPM or 25,000 Gs. This can be made for well under $200 USD now that I have everything figured out.
Here are the tools I used, certainly everyone is not going to have a lot of these (Trust me, you are a smart individual. You can come up with possibly a better way of doing this. Let me know in the comments what you think.)
Computer to program the Arduino
Hot Glue gun
Again, these are the parts I used (Some have links to amazon):
White LED Strip
Dremel with battery and charger (not sure what model but I'm sure you can find one used for cheap on eBay)
Torx bit to take apart the Dremel
3 sheets of 24x12 inch clear acrylic
Vinyl (purely for aesthetics)
91% isopropyl rubbing alcohol
Step 1: Designing the Micro-Tube Holder
All design work on the micro-tube holder can be downloaded at the link below:
Just 3D print the piece using whatever settings you normally use and it should come out great.
It uses 1.5 mL micro centrifuge tubes which can be found on amazon for cheap.
Step 2: Designing the Briefcase Formfactor
I decided to use a briefcase for the housing for all of the components, mainly because it can just be thrown in to the back of a car or trunk and taken wherever without the risk of damaging any parts. The link to the specific briefcase can be found below:
The piece of acrylic in the middle was laser cut using an Epilog 40 Watt laser and I can provide the file for that if needed.
The red plastic standoffs screwed into the acrylic were 3D printed and I can also provide the stl if need be.
Using the original parts from the Dremel and not tearing apart the battery enabled me to remove the battery and recharge it on any compatible Dremel battery charger.
Step 3: Coding...
I have included some of the pictures of the wiring and I can make a wiring diagram but the basic components consist of:
-A few pushbuttons
All of these parts were purchased from Amazon.
The most difficult part of the entire project, which consisted of days and days of coding and debugging. I have provided the code for your convenience so you can either tweak it or just use how it is.
Basically I wanted the centrifuge to operate using one button so anybody could use it regardless of skill level. Pressing the leftmost button powers everything on, while the one directly to the right flashes letting you know that is the button to press to begin centrifugation.
Additionally, I wanted the ability to press and go. Basically you load the samples, press start and leave the device for a pre-programmed amount of time and the centrifuge will stop automatically. The timer function took the longest for me, mainly because I am not fluent in the arduino language. I also had a few people help me out in the process.
I put the program on a loop so you can spin as many samples as you want, or until the Dremel battery runs out.
Step 4: Base and Lid of Centrifuge Housing
These pieces were downright difficult to design and with over 5 iterations printed and each taking over 34 hours to print, I think it would be best if I just gave everyone the files for them. A lot of trial and error in designing the pieces took place, but we started getting more scientific as time went on due to the price of the plastic. Having the base "hug" the bearing on the Dremel shaft was essential because without this feature, the vibration would be too intense. The walls and top of the lid were made using clear acrylic.
Basically all I did was take apart the Dremel and desoldered the motor controller from the motor so it would fit. I then placed the controller in an easily accessible location so it would be a breeze to change motor speed.
For the battery compartment, I took the empty Dremel casing and screwed it back together and cut just the battery compartment off with a band saw so I could easily replace the battery.
The pieces of acrylic go a little bit past the actual lid. This was done intentionally so that the lid would be secure and wouldn't move much.
Step 5: Visual Asthetics
Many considerations were taken into account for when putting the device together. I wanted to make it as visually appealing as possible so any onlooker would take a gander at the centrifuge and want to know more about it.
These improvements over previous designs consist of:
-Creating a see-through bottom acrylic plate that would not only keep components in place but provide anyone with a better understanding of how everything came together. This part isn't made to look good, its just to show off.
-On top of the clear acrylic, a friend of mine that owns a sign shop had some carbon fiber vinyl that she applied for me on top of another piece of acrylic which then went into the laser to get all of the correct holes cut.
-One challenge I faced was the size of the acrylic. The acrylic is 24x12 inches, and the briefcase was slightly bigger. This was combated using a strip of acrylic which was engraved on top to diffuse the light from an LED light strip underneath. Everyone seemed to really like this effect.
-The last thing to do was just clean up. The outside of the briefcase had a bunch of UPC and other random stickers on it which took away from the clean look of the device, and a little rubbing alcohol and uncure (debonder) took care of this quite well.
Step 6: Test, Test, Test.......And Then Troubleshoot.
A lot of problems I faced came from my stupidity in using hot glue to secure everything together not even thinking about if something would go wrong. But thanks to Murphy's Law, "Anything that can go wrong, will go wrong."
Problems I encountered:
-Hot glue everywhere
-Hot glue everywhere
-The V1 light bar looking like garbage
-A wire coming loose
-Hot glue everywhere
Solutions to those problems:
-RUBBING ALCOHOL - I would have never thought to ever use rubbing alcohol to remove hot glue from stuff but doing so solved every problem (mainly because I couldn't fix anything because there was hot glue everywhere.) A little bit of rubbing alcohol on a cotton ball works wonders.
Step 7: You Are Ready to Extract DNA!
1). Load a sample into TWO centrifuge tubes and place them on opposite ends or the motor will go crazy and possible brake from being unbalanced.
2.) Press the leftmost button to power everything on.
3.) Follow the on-screen directions.
4.) Wait specified time, or you can press button in the middle of spinning to stop.
5.) Remove tubes from holder and deposit enough 91% isopropyl rubbing alcohol into the tube to fill it up.
6.) Gently turn the tube upside down a few times and examine your freshly extracted DNA.
7.) Repeat until your heart is content.