A research team from Lawrence Livermore National Laboratory (LLNL) has used a direct ink writing (DIW) process to 3D print property-specific, silicone metamaterials that possess shape memory behavior, which technically makes them 4D printed. LLNL has worked with both 3D printed metamaterials and 4D printing before, but by using a DIW process, the material becomes more lightweight and functional, with a tailored, mechanical response. This can be achieved when printed structural porosity and intrastrand porosity are combined, by adding hollow, gas-filled microspheres into the 3D printing ink. But many researchers are adding different materials to the mix, such as these shape memory polymers, in order to increase the potential applications. Read more at 3DPrint.com: http://3dprint.com/181142/llnl-shape...-metamaterial/