Figure : Schematic representation of a piezomechanical cycle, in which the repeated interconversion between spiropyran (SP, left) and merocyanine (MC, right) is triggered by alternating application of mechanical stretching forces and hydrostatic pressure. The scissile carbon-oxygen bond in SP is marked red. Adapted with permission from Kumar et al., Copyright 2021, American Chemical Society. tions, the lower volume of SP compared to MC is the driving force for the bond formation reaction. The process of alternating activation of SP by force and of MC by pressure can be repeated several times, thus establishing a piezomechanical (or baromechanical) cycle.