Molecular Thermal Engine Based on a Highly Flexible Elastic Crystal

Materials that exhibit actuation behavior in response to external stimuli have a wide range of applications owing to their ability to convert input energy into mechanical work. Light and chemicals are common sources of input energy. However, actuation using thermal energy from ambient-temperature sources remains challenging. In this study, we introduce novel elastic crystals composed of dodecylated porphyrin molecules that exhibit high flexibility and deformation in response to temperature changes. When a crystal is loaded with a small weight and positioned between high- and low-temperature heat sources, it exhibited continuous, large, and rapid oscillations. These oscillations persisted for at least 160 h, corresponding to 3.9 million deformation cycles, as long as the temperature difference was maintained. This study presents the first example of a molecular crystal functioning as an engine that can extract kinetic energy from static and ambient-temperature sources.