Recent advances of dynamic molecular crystals with light-triggered macro-movements

Dynamic molecular crystals showing light-triggered macro-movements have attracted great attention due to their unique ability for light–force conversion. These molecular crystals are driven remotely without any intermediary devices like wires and motors, which can transform light energy into mechanical work directly. However, the limited space restricts molecular rotation and motion in the crystalline state; thus, realizing macro-movements in molecular crystal systems is still a formidable challenge. In this review, we aim to focus on the underlying working mechanism of the photo-controllable macroscopic motion of molecular crystals with special focus on their practical applications. In detail, we discuss the basic principles and macroscopic photomechanical effects of these dynamic molecular crystals, including their deformation (i.e., bending, twisting, curling); complex motion (i.e., crawling, rotating, rolling); and disintegration (i.e., photosalient effect). Then, we introduce the most promising applications of photomechanical molecular crystals in the fields of all-optical devices, crystal actuators, and biomimetic artificial muscles. Therefore, this review will provide inspiration to develop state-of-the-art dynamic molecular crystals by bridging the disciplines of physics, chemistry, and engineering science.