The articulation geometries of the 3D printed parts in my silicone skin prosthetic hand are based directly on the "Flexy Hand 2" model by Steve Wood (http://enablingthefuture.org/upper-limb-prosthetics/the-flexy-hand/).

I liked the Flexy Hand model so much I decided to give it an artistic twist and do some carving in Blender. I uploaded a carved version as a ready to print STL model file: "modified_artistic_flexy_hand_prosthetic_print.stl". It is too big to store on Hackaday so you can find it in the "MODELS" directory of the project GitHub repository (https://github.com/curtpw/silicone-skin-prosthetic-hand)