Battery Operated Centrifuge for Cell Separation in Fluid Suspension.




'We offer a step by step description of how to make a battery powered 9-24 volt DC motor driven centrifuge for separation of cell in fluid suspension for under 20 dollars. This centrifuge may be used in the field (when no other technology is available), and is set in a cookie tin or coffee can to prevent accidental release of content.

Bullet shells act as the "buckets" for the centrifuge.

Paperclips are bent to hold the shell casings, which spin out when the motor begins to turn.

A DC motor speed controller allows control over acceleration and deceleration.

A motor spinning at 2000-2500 RPM with a radius of 2 inches will develop the
600 g of centrifugal force required to separate cells in fluid suspension.

We used 1 milliliter pipettes which fit into the bullet casings to spin-down a "cell pellet"
in a pleural fluid sample however a "virtual tube" of cellophane will also work .

This project was supported in part by the Center for Parabiotics Research.
Project team members: R Siderits, J Jaworski, W Lecorchick, O Ouattara

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Step 1: Finished Prototype

Here is an image of the completed centrifuge. We chose to place the motor, arms, and buckets on the outside of this cookie tin for demonstration purposes. You may choose a larger coffee tin or better yet, a 12" diameter, 2-3 inch deep cookie tin to place it inside.

Use the lid of the cookie tin to completely cover the centrifuge for safety.

The knob on the front of this image is the DC motor control. We used a two part plastic and a bottle cap as a mold for both the rotor head (center) and the speed controller knob.

Step 2: Parts

Here is a list of the parts that we used.
Start with a DC 12-24 Volt flat mount motor
Find a DC motor speed controller (or circuit)
Get a large coffee-can or cookie-tin (12" diameter)
Two 9 Volt batteries
Two paper clips
Two or more bullet casings to serve as "buckets"
Hammer, wood, nail, pointed "needle nose" pliers
Total project time is about 30 minutes

This will run on one 9 volt battery; however, two batteries in series or a 12 volt DC supply will really spin things up to full speed. The paper clips need to be sturdy. The bends and relative looseness help to absorb and distribute imbalances and thereby serve to dampen vibration or precession.

We have included sources for these parts as well as a circuit diagram for the DC motor controller.

Step 3: A Look Inside

These two images look into the cookie tin. The lower half holds the motor speed controller. We drilled a hole in the side of the cookie tin to let the shaft of the controller through and then put the nut on the outside to hold it in place.

The knob is formed from two part plastic (or epoxy, or JB weld) in a bottle cap.

The under surface of the lid shows the wires from the controller going up to the motor.

The motor is set in a hole in a piece of wood and has four small screws holding it to the lid.

Step 4: Computer Model of Prototype

This computer model was done in trueSpace 6.6 by Caligari corporation.

This model with the "Physics" simulation helped us develop the curves at the end of the paperclips and the placement of the hole in the bullet casing.

Step 5: The Rotor Head

These images show a close-up of the rotor head and the paper clips. A line drawn on a piece of paper that corresponds to the shape of the bends in the paper clips will assure that both are identical. We used needle-nosed pliers to bend the paper clips into this shape. The paper clips are set into the holes in the rotor head, not glued. As a matter of fact, there is no glue in this project.

The motor is pressure fit into the hole in the piece of wood. If it's a little loose, then a layer of tape around the motor will snug it up.

The hole in the rotor head is also a pressure fit.

Notice the bend in the "bucket end" of the paper clips. This bend allows the bullet casing buckets to swing out with centripetal force.

The green mark on the top of the rotor head marks the site where reflective tape was placed to measure revolutions per minute (RPM) by using a tachometer.

Step 6: Making the Bucket

These images show how we made the holes in the sides of the bullet casings for the paper clip rotor arms. We made a small wooden jig to hole the base of the casing while we put a small nail into the open end and tapped it with a hammer.

This will put a small hole in the end without distorting the casing. Notice in the first image what happens if you put the hole too close to the rim; it splits the casing.

Step 7: Pipette in Bucket on Rotor Arm Ready to Spin-out

Here is the paperclip rotor arm with the bullet casing "bucket" holding a bulb-down, 1 ml pipette.

When the rotor spins up, the bucket spins out and the fluid in the pipette is subjected to the centrifugal force.

Step 8: Take a Look at These Cell Pellets!

These two pipettes were spun for 5 minutes at about 2500 RPM with a rotor radius (paperclip) of 80 millimeter. This gives a Relative Centrifugal Force (g) of about 500. Not bad for one half dead 9 volt battery. This particular motor would spin up to 5000 RPM and give more than 800 g with a 2 inch radius. This is more than enough force to separate many types of cells in suspension.

The whitish cell pellet at the bottom represents the cells that have been separated from the fluid.

In this case we used a pleural fluid sample that was to be discarded. The separation was surprising.

Step 9: Figuring Out Centrifugal Force

Use of this "nomogram" allows you to determine the relative centrifugal force (RCF) in g's, by aligning the radius of rotation in mm (in this case, paper clip length for the rotor arm measured from the center of the motor spindle to the base of the bucket).

The Revolutions Per Minute (RPM) can be verified with a hand-held tachometer. We used an infra- red tachometer from Harbor Freight.

Step 10: Tips and Learning Points

Use plug in DC power supply instead of battery

Use solar panel (Harbor Freight) to recharge battery

Place a weight on top cover to dampen vibration

Use two part plastic or epoxy resin to make rotor head

Make a virtual tube using cellophane in the bucket

Consider using a tachometer to get a speed check

Make your own speed controller (see references)

Always use all appropriate safety gear!

Step 11: Long Arm Paperclip (14 Cm) With Tachometer

This image shows the "long" paperclip rotor arm (see "arch" to left, beyond lid of tin) which measured up to 14 cm from the center spindle of the DC motor. You can see the tachometer at the top of the image. With two 9 volt batteries in series or a 12-24 volt DC power supply this will "Tach" up to 2000 RPM for about 600 g's. Spinning it up that fast requires that you at least Duct Tape the unit down to a surface (and wear Goggles).

Step 12: This Small Solar Panel Can Recharge the 9 Volt Batteries.

This small solar panel can be used to recharge a rechargeable 9 volt battery. We purchased this type of charger from the Harbor Freight store for 11 dollars.

Step 13: References and Sources

Step 14: Disclaimer

Follow ALL reasonable safety guidelines and actually wear safety equipment, including
but not limited to:
1)  Full body armor.
2) Using a centrifuge that spins really fast. 
3) Powertools that you never read the instructions for.
4) All tools that you never learned to use properly.
5) Anything that heats up, pinches, cuts, squeezes, flies      off, carries electric current or causes other     traumatic, caustic, or thermal injury.  
We are sharing our experience, not telling you to do it.  
If you choose to try this then - it is at your own risk!
  • No really, we're not kidding about this.

Step 15: What Can This Project Be Used For?

Aside from a hobby or "field" solution for separation of cells in fluid suspension, this
prototype device could be used (in the absence of any other technological solution) for
initial sample preparation of cytology specimens.
There may be a demonstrable need for this capability in supporting evolving health care infrastructures in countries with restricted economy.

For example, in "developed" nations the PAP smear for cervical-vaginal cytology has decreased the incidence of cervical carcinoma by approximately 70%. However, in a country with
restricted economy this is not the case. A woman may need to transport a cervical
cytology specimen herself, sometimes hundreds of miles, and then wait months for the
sample to be prepared and interpreted.

Providing a basic functional centrifuge for cytology slide preparation may help facilitate
aspects of this difficult process.

Step 16: Watch It Spin!

This video segment shows the movement of the buckets as the motor speed is gradually increased.

Step 17: Good Luck!

We hope that you've enjoyed this How-To and that it may be useful to you.

The potential for this prototype to be used in remote areas in countries with restricted economy for use in supporting cervical vaginal cytology field preparation of sample may help to provide critically needed services for these populations.

Good luck and be safe (remember to build yours INSIDE of a cookie tine, not on top).

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    31 Discussions

    arun kelkar

    6 years ago on Introduction

    This centrifuge, with certain modifications, can be used for clarifying home made wines.
    arun kelkar

    DIY Dreamer

    10 years ago on Introduction

    As a medical professional who uses centrifuges extensively daily, I found this project clever and interesting, BUT using this for biological material other than plants is incredibly dangerous. Full body armor is not sufficient to protect you from the diseases at large in the general population to which this centrifuge guarantees you will be exposed. Biological aerosols are nothing to fool around with.

    4 replies
    jexterDIY Dreamer

    Reply 9 years ago on Introduction

    I would agree that using this in a medical diagnostic lab or equivalent would be unwise, but saying that using it for anything "other than plants is extremely dangerous" seems extremely cautious. There are any number of non-hazardous uses for a small centrifuge in biological and non-biological lab settings. The majority of clinical centrifuges are used in a non-clinical settings, on both prokaryotic and eukaryotic cells, and it's routine, not extremely dangerous. "Biological aerosols" are indeed nothing to fool around with; that's why I'm much more concerned about the guy sneezing in the elevator than the SF-9 or Top-10 cells I'm centrifuging in the lab ;^)

    sideritsDIY Dreamer

    Reply 10 years ago on Introduction

    Your point is well taken and I agree. Here are some thoughts that I had in offering this project Bottom line, we are talking about balancing moral and ethical justification for exploring low cost alternative healthcare technologies in an effort to reduce human suffering in countries with restricted economy, against the risk/benefit of actually utilizing them. As with many projects on this site that spin many times faster, use combustibles or high voltages, this project has inherent risk (even for "botanical" specimen processing). However, we may also consider the reality that for impoverished societies with rural populations new cytology methods that only require centrifuge processing for on-site cytology screening could make a huge difference in the ability to provide any aspect of woman's health care (try for example using an egg beater centrifuge). It is also important to consider that lower speeds, protective encasement, alcohol suspension, sealed pipette tips and longer spin times can be used to increase safety. By the way, having used a series of "coffee-can" prototypes, I was amazed how well these things actually work, especially with the upside down pipettes ( heat sealed at the tip with a hand held 1" hot-wire bag sealer or para-film). Finally, I would be grateful for your opinion, as someone who is familiar with this technology, would you be able to suggest any design modifications (for non-medical use)? We were considering an interlock for the arms or a rigid rotor head with a pin to hold the casings. The design parameters are <10$ and does not require "machining" of parts. Best regards and thanks for the comment.

    DIY Dreamersiderits

    Reply 10 years ago on Introduction

    How about mounting the spinning centrifuge head in something like a tupperware cake container. Sealable to contain those potentially deadly aerosols. Easily cleaned of those inevitable leakages. You will be profoundly appreciative to have added this feature once you see what a huge mess a leak makes and realize what might have happened if you breathed in a lung full. And once you see how often this type of incident occurs. It probably will be resilient enough to contain a failure of the centrifuge head itself.

    sideritsDIY Dreamer

    Reply 10 years ago on Introduction

    Excellent idea. One leak is all it takes. We also think that the spent primers should come out if they contain any residual chemicals. We were intending it to go inside the cookie tin and only put it on top for the DEMO, but your idea fits better with clean-up and safety. Thanks!


    10 years ago on Introduction

    i drill holes in the blades of a fan then put test tubes in and turn the fan on itx=s back]]great ible 5 stars

    1 reply

    9 years ago on Introduction

    Very elegant design and looks very sturdy.  I have created another centrifuge using computer cooling fan and foam plate/bowl. The six place computer fan/foam centrifuge can run up to 920 rpm when two 3.5 mL tubes loaded.  It will allow total 21 mL of samples to be processed at a time but the speed will drop down to 250rpm.  That should be good enough for low speed applications, such as pond life observation.

    Just to share my design with you:

    1 reply

    10 years ago on Step 17

    This is a great idea for junior high school age science projects on up to adult microscopy hobbiests who with to collect protozoa, check sedimentation of ponds or lakes and about 25000 other uses!!

    1 reply

    Reply 10 years ago on Introduction

    Thanks, just make sure that the take home point is that when you make one, it goes inside of a cookie tin that is on top of the smaller battery-controller tin. Its safer that way.


    10 years ago on Step 17

    No offence was intended, i've removed the comment. I still think my post raised some good points, and it was meant to be slightly funny, not vindictive. I didn't get your disclaimer joke first of all and thought you'd made a typo. I found the idea of having to make a centrifuge out of bullet casings in some sort of emergency situation comical..just imagining how the situation could arise..

    1 reply

    Reply 10 years ago on Step 17

    Now that you point it out, it's comical... I've been laughing about that for an hour. I didn't mean to offend you either. Guess I'm still getting accustomed how these things should be posted for a large audience. You did raise excellent points and we should have been a little less superficial about something that could be dangerous or misused, especially in combat (just kidding) :). Thanks for you response.


    10 years ago on Introduction

    Just wondering, aside from remote-location cell culturing, what other applications would there be for a battery-operated centrifuge? Just looking for ideas here...

    1 reply

    Reply 10 years ago on Introduction

    Mostly for layering or separation of cells in suspension or separating liquids that don't mix well. It can be used to wash cells or "sediment out" things that you don't want.


    10 years ago on Introduction

    What a great idea! I would consider building this to separate yeast out of active brewing projects for storage and later re-use. Beer is the second best (after modern medicine) application of microbiology after all...

    1 reply

    Reply 10 years ago on Introduction

    Wow, never thought of that. I wonder if it would "layer" on top of an oil or underneath. The speed controller would let you go slower for more time. By the way, a hand crank flashlight (hacked) will produce enough energy to run a smaller motor, if batteries are unavailable or cannot be recharged from the solar panel.


    10 years ago on Step 6

    I really appreciate you posting this instructable. It will be great to build for my school science department.


    10 years ago on Introduction

    really good, looks like it works really well too! another safety note i'd just like to mention: inspect your centrifuge components for wear (particiularly the swing buckets and paper clip rotor assembly) after each and every operation. If anything looks slightly worn in the interests of your own safety it is best to replace it. this is a standard safety practice for commercial centrifuges too. If people don't do it, and a rotor shears, it can literally go through a few concrete walls before it will stop (and in fact the only safe place to be if this happens is directly above or below the centrifuge, as these are unlikely trajectories for projectiles). if you run it in a thick wood/steel box it should be pretty good for the small mass swing buckets. (google centrifuge rotor break for examples of what can happen) 5*'s :)