Gel electrophoresis

Gel electrophoresis is a method used to sort macromolecules or fragments of DNA or RNA. A sample is placed in a gel that allows these molecules to travel through, then an electrical charge is applied at both ends. The phosphates within the nucleotides naturally give the samples a negative charge, causing them to repel the negative electrical current and travel through the gel to the end with the positive charge.

A DNA ladder is a sample with sizes known in advance and is included separately in one of the wells in the gel. Smaller fragments are able to move faster and farther allowing their sizes to be measured by the distance they traveled when compared to the ladder.

tl;dr Scientists look at DNA by electrocuting jell-o.

The electrophoresis combs I have designed here are used to create the gels. A liquid solution is poured into a tray and a comb is put in place while it solidifies. The comb is removed leaving a negative space for the samples to be deposited.

For more information on how electrophoresis works, here is a quick video that should help explain.

Customizable comb

Various projects have their own needs and laboratories have their own preferences. This can be more wells at once, or larger wells that hold greater volumes. Creating the comb in OpenSCAD makes it easy to change the style of the comb. A computer novice should be able to understand enough about the program within an hour or so to get a working STL file they can then print. As long as you know the measurements and account for the overall width, this design should allow anyone to make their own comb anyway they desire.

OpenSCAD is a free open source program available on Mac, Windows, and Linux.

Pricing gouging

Another reason that I wanted to create a 3D model of this comb is the price. These combs are nothing fancy, just plastic. Bio-Rad, one of the largest vendors for electrophoresis equipment charges about $60 per comb. Gelcombs.com offers discounted versions that sell for $45 each. Neither of them offer options to make custom combs.

I have them available on Shapeways for purchase in acrylic only at about $19 each. There is a $1-$3 markup, but you are welcome to download the STL files and print them on your own. The acrylic is printed in wax so they have a waxy film on them when they arrive from Shapeways. Wax melts above 37°C (99°F) and acrylic melts at 160°C (320°F). Running them through a phase 3 autoclave wash, or maybe a consumer dishwasher should remove the wax.

Shapeways does offer a cheaper type of plastic priced as low as $5.15 each, but that material is too porous making it difficult removing the comb from the gel. Printing this model on a consumer 3D printer should cost under $1 each, and may require sanding or an acetone wash to smooth the model out enough so it doesn’t damage the gel.

If you are not purchasing them from my store on Shapeways, I highly recommend you hold off on any bulk purchases and see how smooth they are.

Using this model

The code for the electrophoresis combs can be downloaded at GitHub and are available for on-demand purchase from Shapeways