Stretching, reversed

Early this week, Northwestern Physics undergraduate Zachary G. Nicolaou reported on some peculiar material properties in Nature Materials. What makes these materials unique is how they respond to tension and compression. For most materials -- metals, plastics, ceramics -- the typical response is to extend and contract, respectively. For Nicolaou's materials, the opposite is true. That is, when these materials are tensions, they contract, and when they are under compression, they expand. Counter-intuitive to say the least. "Materials are networks of connected constituents, and when you apply tension or pressure, they can respond in surprising ways," said Adilson E. Motter, Nicolaou's advisor and co-author on the paper. Though they have no specific applications in mind, the pair of researchers anticipates there could be a variety of uses for this new kind of metamaterial, particularly in the world on MEMS.