OctaWorm is a deformable octahedron burrowing robot that is currently powered by air pressure. It is developed by Juan Cristobal Zagal and has many 3d printed parts. The design enables it to move in very confined spaces.
Here is a video showing its abilities and a development path of OctaWorm from early hydraulically powered prototypes:
Here you can see it moving trough a pipe:
Extensive paper on the project:
Hopefully Juan will open source the designs :-) Great work Juan!