Here is my Borg prosthetic arm from Star Trek. The cylindrical parts have 5mm gap so you can use hair dryer to warm up the plastic and adjust the size to fit your arm or you can scale it if you like.
The arm contains 8 pairs of 3mm LED's taht are glued on the surface and also 2 servo motors (SG90), See video: https://www.youtube.com/watch?v=ZL4FHzn_UvY
All is powered by Arduino nano and 9V battery (code and schematic attached).
I didn't hide the wires on purpose so it looks more Borg LOL. I also glued few electronic components (painted with metallic copper) and I added few black 5mm elastic tubes.
Any suggestions for improvements or upgrades are welcome \//
Physics, 3D printing, Programming, Astronomy and Sci-fi - that's me \//