3D printed C60 and C70 molecules



3D buckyball



Note I: The 3D printed 3-way connectors used to make these Fullerene models can be downloaded via the links at the end of this article where you can find the OPENScade files I used to create the connectors as well as the .g files that can go directly to the 3D printer. To speed things up the .g file will print out 12 connectors at once.

Note II: As these are small parts please remember to let the parts and printer bed cool before removing them - otherwise being hot, they will warp and bend when removing them.

Note III: these are very simple 3D printed parts and much more detailed and more 'beautiful' atoms (e.g. half sphere balls etc.) could be made. I have chosen a very simple design because it prints out fast, so a teacher for example can print out as many parts as needed as quickly as possible for a class or science club activity.

Fullerene models
The C60 molecule is composed of 60 vertices (corners), 90 bonds (edges) with 12 pentagonal and 20 hexagonal rings (faces). The mathematical name for a this shape, which is also a football, is a truncated icosohedron. Each vertex corresponds to one of the 60 atoms in the molecule and has three bonds (edges) radiating out from each corner (atom).

As each atom has three bonds and each bond is shared between two atoms, we must have 3/2 the number of bonds 3/2 x 60 = 90 bonds / edges. In the molecule 60 of these are 'single' bonds while 30 are 'double' like (so shorter). All the single bonds are in pentagon rings, while all the double bonds are between pentagons (i.e. in hexagons). These double bonds can be broken creating a fascinating range of substitution reactions.

A 3D printed model
Here we use 3-way 3D printed connectors to make up molecular models of the fullerenes (e.g. C60, C70 etc.). I used short lengths of flexible 6 mm plastic tubing as the 'bonds' that push-on / join up to the 3D printed connectors.

You can use all the same colour and length tubing or alternatively use two different colours to represent the double and single bonds in the molecule. For C60 I use 90 pieces of tubing (30 double and 60 single bonds). The easiest way is to join up 5 pieces of tubing to 5 of the 3-way 'atoms' to create a pentagon. Make up 12 of these pentagons. Then join up each pentagon to another pentagon with a single piece of tubing to create the C60 football molecule. You could of course scale-up each 3D printed connector (and use larger tubing) to create larger C60 models.

C60 - a truncated Icosahedron

Flat sheets & pentagon curvature
You can cover a floor, or other flat surface with triangular, square or hexagonal tiles. Pentagon rings (5 sided polygons) cause curvature of the surface. 12 pentagons will completely wrap-up a flat sheet into a spherical ball or cage. 12 pentagons on their own make a dodecahedron. If you put an extra edge between each pentagon you get a truncated icosahedron or more commonly a soccer ball (12 pentagons and 20 hexagons). As you add more hexagons to the 12 pentagons the cages become larger and more icosahedral in shape.

Summary - there are 60 atoms, 30 double and 60 single bonds in C60

How to make a C60
what you need: 60 x 3D printed 3-way connectors
90 tubes (e.g. 60 black, 30 transparent)

1) join five of the 3D printed 'atoms' to five tubes to create a pentagon ring (remember its 5 sides not 6).

2) make up 12 of these rings seperately (once this is done you have used up the 60 atoms)

3) join up a pentagon ring to another pentagon ring using a single piece of tube

4) continue to join up pentagons to each other.

5) make sure you don't make octagons (three pentagons and three tubes will create a hexagon)

6) the C60 molecule will form in your hands ...

How to make a C70
what you need: 70 x 3D printed 3-way connectors
105 tubes (e.g. 60 black, 35 transparent)

1) join five of the 3D printed 'atoms' to five tubes to create a pentagon ring (remember its 5 sides not 6).

2) make up 12 of these rings seperately.

3) take one pentagon and add five tubes to it

4) add five pentagons to the ends of these tubes

5) join across from pentagon to pentagon to make a bowl or cup shape

6) repeat steps 1) - 5) to create a second bowl or cup (if you add these two together it will make C60)

7) add tubes to one of the bowls and add a further ten 'atoms' in a ring, on one side has 40 atoms.

8) add the other bowl shape to this to create the C70 rugby ball fullerene.

A Geodesic Dome
related to C60 are Geodesic domes - a half a cage / ball. As its half a ball we only need six pentagons. A dome with a convenient flat base (that can sit stable on the ground) can be made using six pentagons and 10 triangles. There is a pentagon on the top of the dome with five other pentagons radiating outward forming the side walls of the dome. Between each of these five pentagons are a pair of triangles. The edges follow great circles around the dome taking the shortest path between the spherical surface connections. The Geodesic is the shortest path between two points, so the dome is a geodesic dome. See link below for a 3D printed Geodesic dome model.



12 three way connectors:
".stl" file
".scad" file
".g" file
more
soon
3D
Geodesic
Dome
back to
3D page


THE CREATIVE SCIENCE CENTRE


Dr Jonathan Hare University of Sussex, Brighton.
e-mail: j.p.hare@sussex.ac.uk

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