Global Performance Indices for Dynamic Crystals as Organic Thermal Actuators.

Crystal adaptronics is an emergent materials science discipline at the intersection of solid-state chemistry and mechanical engineering that explores the dynamic nature of mechanically reconfigurable, motile, and explosive crystals. Adaptive molecular crystals bring to materials science a qualitatively new set of properties that associate long-range structural order with softness and mechanical compliance. However, the full potential of this class of materials remains underexplored and they have not been considered as materials of choice in an engineer's toolbox. A set of general performance metrics that can be used for quantification of the performance of these prospective dynamic materials as micro- and macroactuators is presented. The indices are calculated on two selected representatives of thermosalient solids-materials that undergo rapid martensitic transitions accompanied with macroscopic locomotion. Benchmarking of their performance against extensive set of data for the existing actuator classes and visualization using materials property charts uncover the hidden potential and advantages of dynamic crystals, while they also reveal their drawbacks for actual application as actuators. Altogether the results indicate that, if the challenges with fabrication and implementation in devices are overcome, adaptive molecular crystals can have far-reaching implications for emerging fields such as smart microelectronics and soft microrobotics.