This is an early prototype for a soft robotic tentacle. These files form the mold, in which you cast two part RTV silicone. These were printed on a modified Z-Corp printer, with Viridis' material MakerDust forming the outer shell, and corn starch forming the inner core.

You can find more details on http://har.ms/category/blog/soft-robots/

Print two copies of the outer mold, and one copy of the inner core in a soluble material like corn starch. Alternatively you can print an inner core, cast it, and duplicate it in wax to form a soluble core. Then, assemble the mold together with 1/4-20 bolts and pour two part RTV silicone into the void. I used Smooth-On MoldMax for one of the more successful prototypes.