The 4D printing concept draws inspiration from nature which already has the ability to self-replicate.

BBC: TED 2013: 4D printed objects 'make themselves'

The slick and bendable Nylon 6 melts at 320 degrees celsius, roughly 100 degrees higher than the more common and brittle ABS. The flexible nature of nylon has some obvious advantages, particularly when printing tubing or even an iPhone case.

ENGADGET: 3D printing gets more flexible with Nylon extrusion Alt