A novel dynamic organic salt crystal that displays a thermosalient effect and unusual locomotion

Thermally induced locomotion, such as hopping, walking, crawling, and wriggling, in single crystals is rare. It has potential applications in designing smart mechanical devices. Here, we report jumping and cracking followed by the fragmentation of an organic salt, piperazinium tetrafluoroterephthalate (TFPPZ), above 150 °C due to colossal anisotropic thermal expansion. Above 180 °C, the crystals show further jumping, followed by spinning and running due to rapid sublimation of the salt into individual components. The locomotive speed of the crystal is the highest reported to date. Hot-stage microscopy, single-crystal X-ray diffraction, and sublimation experiments were performed to study and rationalize the extended locomotion of the crystals beyond jumping.