Design of a color changing shape memory actuator

Abstract

Shape Memory Alloy (SMA) uses heat energy for actuation, there is a need for it to indicate its temperature through color change in order to avoid overheating. Therefore, in this work, a smart wire that changes color when actuated is designed and developed using thermochromics which are active mixture containing leuco dyes that is solid at low temperature but which melts at high temperature, causing the dye to change from one color to another when subjected to high temperature. Since thermochromic materials cannot be directly applied to an SMA's surface because the dyes have a slurry form and are water soluble, the thermochromic material is microencapsulated into a polymer and then applied to the SMA wire. In this work, an elastomer was impregnated with thermochromic materials in dye form to produce a color-changing polymer with which the SMA wire is coated with. The results show that the developed color changing Shape Memory Actuator not only exhibits the properties of a SMA wire but also able to give a visual indication of high temperature through its color changing properties.