Proportionnaly accurate magnetic DNA model

This entire DNA model is composed of a repetition (of your choice) of basic nucleotides with both double and triple hydrogen bonds.

The helix diameter on the pictures is 20 cm.

The triple bounded Cytosine (C)  and Guanine (G) have to be printed from the “CG” model with two different colours (respectively grey and blue in the photos). The double bounded Adenine (A) and Thymine (T) have to be printed from the “AT” model with two other colours (respectively red and green in the photos).

The two 3D models are available as step files, 3mf files (for Prusament PETG and including no-supports zones inside the magnet holes) and gcode files (produced from the 3mf files). You can copy-past multiple nucleotides from the same colour on your bed to simplify the production process.

The FreeCAD parametric file is also available with a "Spreadsheet" regrouping key parameters (if you want another proportion rate instead of one centimetre for one ångström for instance or the dimensions of the magnets or silicon tubing).

On top of the 3D printed nucleotides, you will need two types of neodymium magnets with the same diameter and a difference in length (4x7 and 4x10 mm in my case). You will also need a silicone tubing (3 mm in my case) or any other string or rope. The silicone add some bouncing movements and it looks less rigid.

When the individual nucleotides are printed, you need to thread them onto the silicon tubing like beads for the first DNA strand in the specific order you want to use.

Then you can glue the short and long magnets who will act in place of the hydrogen bounds inside the magnet holes. Opposite magnets have to be one short and one long. You can see in one of the picture the magnetic polarity of my placement preventing two consecutive “layers” of bounded nucleotides to attract one another. The long magnets should protrude as they constrain the nucleotides avoiding them to twist and pop open.

When the first DNA strand is done, you can then thread the other strand one  nucleotide at a time and glue the second set of magnets in place.

Note: in the polarity configuration I used, the C and G can be thread easer way but the A and T have a specific direction so if they don't match, on of them should be reversed.

Note 2: you can print as many nucleotides as you want to make a really long DNA molecule if you want. You can also genetically encode a message made of one letter representations of amino-acids.

Note 3: you might already noticed from the poster on the back of the pictures, the pictures as mirrored as I failed the first model I printed who append to be a double stranded DNA helix going on the wrong direction. The uploaded models are the corrected ones (only minor correction in the FreeCAD parametric model).

Note 4: the FreeCAD model is made of 3 different parts: (i) common sugar/phosphate part, (ii) double bounds nucleotide and (iii) triple bounds nucleotides. When exported, the common part and the specific nucleotide part are still two different 3D objects and should be moved together.