Integrating 2D elasticity and elastoplasticity into a multi-stimuli-responsive crystal through phase transitions

Practical applications of flexible crystals are often limited due to their monotonous properties. In this study, multi-stimuli-responsive crystals of isonicotinamide (INA), which astoundingly respond to all mechanical force, heat and humidity, are reported. Moreover, the conversion of mechanical properties from two-dimensional (2D) elasticity to elastoplasticity in one single crystal is implemented through phase transitions. Temperature and humidity are both the triggers of phase transformations accompanied by crystal elongation, deformation and displacement, which endows INA crystals with temperature/humidity-reliant dynamic properties. Interestingly, the heat/humidity-induced dynamic motions can be controlled by coating silicone grease onto crystal surfaces. Our work explores the structure properties of multi-stimuli-responsive crystals of INA integrated with different mechanical properties, which is important for the design of flexible materials with manifold properties.