Dremel Centrifuge

I needed a centrifuge to show if a commercially available cleaning solution had any insoluble components in it that would causing streaking. So I decided to build a very simple one based on a Dremel rotary tool.

I cut some 1" diameter underground sprinkler system pipe to a length suitable to contain the standard conical 15 mL polypropylene centrifuge tubes and screwed on some sprinkler system endcaps. I weighed them on a kitchen digital scale and sanded down the heavier one until both were the same mass.

Using some angle aluminum, I determined the exact center with some digital calipers, drilled and tapped thread for 8/32" machine screw. I removed the thread from the machine screw with a belt sander until it was about 3.1 mm in diameter or equivalent to the diameter of a typical Dremel bit. I tightened the screw and bonded it with cyanoacrylate glue (Krazy Glue).

The centrifuge will have a swinging bucket design and my initial use with copper wire to hold the buckets to the angle aluminum failed miserably when it snapped under rotation. Using braided stainless steel wire was the natural solution.

Step 1: Centrifuge in Action .....

I cut a 2" hole in a sheet of clear lexan which I placed over the kitchen sink. The centrifuge buckets were threaded through the hole and the Dremel fixed vertically with a woodworking clamp.

Step 2: Determining Speed of the Centrifuge ...

I was curious at what speed the centrifuge spun at. The Dremel is rated at a maximum speed of 35,000 rpm but I assumed the extra load on it would slow it down considerably.

It's very simple to construct a LED Arduino strobe and alter the frequency of the flashing and use it like an auto mechanic's timing light to determine rotational speed.

Even at the lowest Dremel setting the strobe was flashing every 8 milliseconds which corresponds to about 7500 rpm. Clearly the torque of the Dremel motor had no problem dealing with the additional load. Even at this speed it is generating in excess of 9000 g of force!!!! Mitochondria in cellular extracts can be sedimented at this force within 10 minutes of centrifugation.

Step 3: Results!

I'm adding this addendum in response to a comment about whether I detected any particulate insoluble material in a very familiar blue colored glass cleaning product. Indeed, there was a definite precipitate. The top image is before centrifugation. I theorize that his material reflects detritus present in the bottle manufacturing factory getting inside the bottle and not really a component of the cleaning solution. In any event, a valid reason not to use it on expensive optics - windows are ok!