Because my fursona has 2 thumbs (one of each side of fingers) and humans have only one, I need to do something with it. At first I was thinking about using servos and flex sensors but then I decided to do it with pull rods (similar to Bicycle Brake). I need to connect my real finger with the artificial one. To synchronize their movement, I need to cross the rods - top of my thumb will be bottom of the artificial one (and vise versa). I wanted to use 3D printer but I would have to make 3D model which is hard (to get the shape right and printable). Then I was thinking:
There must be easier, better way to do it.. Yes, there is. I can create mold of my hand(s) and bend plastic over it. It will get the right shape of my hand and I can attach (glue) guiding holes (FreeCAD File) for the rod. Sadly there is no easy way to make the finger itself. I created 4 parts (FreeCAD File) which should be glued together with right rotation (and the bevelled one should be attached to side of the hand). I do not recommend you printing any of FreeCAD Files above (that is why I did not provide other file formats) because I did not verified its' dimensions (did not print it myself yet).
