Rotaxanes are dumbbell-shaped molecules that are capable of converting input energy in the form of light, heat, or altered pH into molecular movements - in other words, they move in response to an external stimulus. They're also known as nanomachines. Dr. Chenfeng Ke and his lab at Dartmouth College have used rotaxanes to design a super-strong smart material. By 3D printing the nanoscale molecules, they were able to create a macro-scale polymer lattice cube capable of lifting 15 times its own weight - the equivalent of a human lifting a car. Read more at 3DPrint.com: http://3dprint.com/168920/dartmouth-3d-printing-4d/