Truss-type systems exhibiting negative compressibility

Abstract

We propose novel two- and three-dimensional truss structures made from rods of different materials connected together through pin-joints to form triangular units which can exhibit anomalous compressibility properties. In particular, we show that these systems may be made to exhibit negative linear compressibility along certain directions or compressibilities that are even more positive than any of the component materials, i.e. the end product is a system with tunable compressibility properties that can be tailor made for particular practical applications. We also show that in specific cases, these systems can exhibit an overall negative area compressibility and sometimes even negative volumetric compressibility (i.e. negative bulk modulus) thus confirming that this property can indeed exist.