A research group at Lawrence Livermore National Laboratory has produced ultrastiff ultralowdensity metamaterials by 3D printing of microarchitected microlattices.
This is very cool - they do additive 3D printing using microstereolithography with nanocoating and postprocessing and can make self-similar lattices with densities varying by several orders of magnitude in bulk density but near constant stiffness.
Construction material can be metal, ceramic or polymer.
LLNL engineered microlattices from Zheng et al Science 344 1373
The lattice geometry can be controlled to choose what mechanical property to optimize.
Scaling this process up and going to bulk manufacturing with hybrid lattices will lead to some pretty amazing materials - combine it with electrostatic control of lattice folding and some active chemistry and this can lead to some pretty science fictional smart material.
Be fun to see if the specs are getting in reach of those needed for a space slingshot or a full space elevator.
Result is "Ultralight, ultrastiff mechanical metamaterials" Zheng et al. Science 344 1373 20 Jun 2014
3D printing microstructures with lasers and photon-sensitive materials
LLNL video
This would be on my list of one of the most interesting applied science developments of 2014