16: Review of Smart Mechanochromic and Metamaterials

Chapter 16 reviews two recent families of smart materials, namely mechanochromic materials and mechanical metamaterials, respectively. Mechanochromic materials change their optical properties and, in particular, their photoluminescence characteristics, if subjected to mechanical loading or interactions with their environment. Chemical and physical molecular changes across various length scales and the rearrangement of molecular chemical bonds to modifications in molecular arrangements in the nanometers regime generally trigger mechanochromic characteristics. Metamaterials are defined as materials that are not ordinarily produced in nature. Note that “meta” means “beyond” and metamaterials have properties that go beyond those of conventional materials. Metamaterials are nanocomposite materials made up of periodically repeated micro or nano units of metals, alloys, and plastics that exhibit properties different from the natural properties of the participating materials. In the following sections, these families of mechanochromic and metamaterials are further described.