” In the not-too-distant future, it may be possible to 3-D print virtually anything. Consider standard printers, which “synthesize” thousands of colors by using only three color cartridges. By analogy, future 3-D printers may be capable of synthesizing thousands of different material properties with a mere handful of material cartridges. This concept inspired a group of researchers from the Karlsruhe Institute of Technology (KIT) in Germany and the French National Center for Scientific Research to explore such development of one mechanical property called effective static compressibility. As they now report in Applied Physics Letters, from AIP Publishing, by using a single cartridge it’s possible to print a metamaterial which expands in size under hydrostatic pressure, even though it’s made up of material which normally shrinks under hydrostatic pressure. In principle, there is no limit to the negative value this material’s effective compressibility can take.”