Your Science Zine

Cheapass science – DIY Vortex Mixer Tube Holder

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The protocol I use for collecting human DNA samples requires tubes to be vortexed for 10 minutes.  Standing around for a sixth of an hour is not my idea of fun so I decided to get a foam tube holder.  Unsurprisingly a piece of foam with holes in it costs 50 dollars.  As per my usual I wanted to be a cheapass and thus I built my own foam tube holder with some things I had lying around.  If you want to see the DIY tube holder in action, watch the youtube video below and scroll further down for instructions for building your own.

 

Guide

 

Compatibility

Before attempting this guide make sure your vortexer will work with this method.  Check the type of head piece present on your vortexer, consult the diagram below for an example of two different types (#12+13 and #14).  This guide works for vortexers with head pieces that match #14. New vortexers usually come with both of these pieces and used vortexers (like the one I bought) may only come with one type.

Materials

The tools and consumables I list are not absolute. Use your noggin and substitute if necessary.

  • Tools
    • Dremel (a drill can be used for some steps but not for carving foam)
      • Sanding bits are needed for foam carving (see image below)
      • Cutting tool
      • Drill bit
  • Ruler or measuring tape
  • Hand saw
  • Marker
  • Compass (optional)
  • Consumables
    • Foam block
    • plastic box (I used a large pipette tip box that was 4”x5”)
    • Rubber bands

These are the two dremel tips I used to carve the foam.

 

Instructions

Two types of modifications need to be done to the plastic box.  First, a hole needs to be made in the center that will allow the vortexer head to poke through.  This alteration will prevent the tube holder from wobbling off of the vortexer head.  For my vortexer the size of the required hole was 1-1/4”.  The second modification is the addition of 4 grooves to the top of the box so that the rubber bands do not slip.

Prior to drilling and cutting grooves.  Yellow circles indicate approximate target locations for the grooves.

After drilling and cutting grooves

 

Close-up of the grooves

How the box fits onto the vortexer head.

Now it is time to carve the block of foam.  My box was not perfectly square; the top of the box (the opening) is larger than the bottom of the box.  This odd shape can be ignored but do make sure to use the top of the box for determining the foam block size.  I made a block that was 4-1/4” x 5-1/4” x 2”.  It is very important that the width and length match or slightly exceed the size of the box so that the foam sits tightly inside the box.

My block

My original block was too tall.  Rather than cut grooves in the foam for the rubber bands and have a tall block (which is preferable for large tubes), I decided to cut the foam down so that it was flush with the box.

Carving and cutting the holes in the foam can be frustrating. Make as few cuts and holes as possible because with each tear the foam becomes more likely to get caught on the Dremel bit and then it will twist and tear the foam block.  Also note that the edges of the foam block are likely to get caught by the Dremel bits.

I used sanding bits to make the holes you see below.  I started with the cylindrical dremel bit I pictured in the materials section.  I went into the block about 0.5” with the cylindrical drill bit (this made the cleanest looking hole opening) and then I switched to the conical bit which I used to go straight down to the bottom of the tray.  Use tubes to test each hole you make to ensure they fit.  A snug fitting tube is better than a loose fitting tube.

When the Dremel grabs the foam and twists some areas of the block will be torn.

Another view of the finished block.

 

All that is left is to attach the box to the vortexer and for that we just need rubber bands.  The way the rubber bands rest on the vortexer head and on the box is important, consult the images below.

The first rubber band is hooked under the left side of the vortexer head and hooked over the right side of the box.

The second rubber band is a mirror of the first rubber band.

 

That is it, the attachment is finished.

Before

After

Glamour shot

If you build a vortexer attachment send me a picture and let me know how it turns out.

 

0 Comments

  1. Curious George January 21, 2012 Reply

    Maybe a dumb idea but can you do something to foam to make it easier to drill holes in? Like compress it or freeze it or cover it with a layer of heavy tape…you get the idea. Make it less easy to tear up.

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