Helicity-Biased Light-Driven Rolling of Twisted Crystals

Area of Science:

• Materials Science
• Crystallography
• Photochemistry

Background:

• Achieving controlled, long-range dynamic motions in molecular crystals is a significant challenge.
• Existing methods often lack precise control over displacement and directionality.

Purpose of the Study:

• To report a novel light-driven rolling motion in twisted molecular crystals.
• To explore the mechanism and parameters influencing this new motility paradigm.

Main Methods:

• Synthesis of twisted single crystals of 9-cyanoanthracene.
• UV irradiation experiments to induce and observe crystal motion.
• Systematic investigation of parameters affecting rolling velocity and trajectory.

Main Results:

• Twisted crystals exhibit rapid, directional rolling toward UV light.
• Rolling is driven by a light-induced center-of-mass shift generating torque.
• Rolling velocity is tunable via light intensity, angle, and crystal dimensions.
• Chirality influences rolling trajectory under lateral constraint, demonstrating helicity-dependent deflection.

Conclusions:

• Rolling motion represents a novel mode of crystal actuation.
• Synergistic harnessing of structural chirality and photoreactivity imparts directionality.
• Findings provide a foundation for developing smart materials with programmable functionalities.