Light-Powered Autonomous Flagella-Like Motion of Molecular Crystal Microwires.

Affiliation

Tong F(1)(2), Kitagawa D(3), Bushnak I(4), Al-Kaysi RO(4), Bardeen CJ(1).
Author information:
(1)Department of Chemistry, University of California, Riverside, 501 Big Springs Road, Riverside, CA, 92521, USA.
(2)Current Address: Key Laboratory for Advanced Materials and Joint International Research Laboratory of Precision Chemistry and Molecular Engineering, Feringa Nobel Prize Scientist Joint Research Center, Frontiers Science Center for Materiobiology and Dynamic Chemistry, Institute of Fine Chemicals, School of Chemistry and Molecular Engineering, East China University of Science and Technology, Shanghai, 200237, China.
(3)Department of Applied Chemistry, Graduate School of Engineering, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka, 558-8585, Japan.
(4)College of Science and Health Professions, King Saud bin Abdulaziz University for Health Sciences, and, King Abdullah International Medical Research Center,
(Nanomedicine), Ministry of National Guard Health Affairs, Riyadh, 11426, Kingdom of Saudi Arabia.

Abstract

The ability to exhibit life-like oscillatory motion fueled by light represents a new capability for stimuli-responsive materials. Although this capability has been demonstrated in soft materials like polymers, it has never been observed in molecular crystals, which are not generally regarded as dynamic objects. In this work, it is shown that molecular crystalline microwires composed of (Z)-2-(3-(anthracen-9-yl)allylidene)malononitrile ((Z)-DVAM) can be continuously actuated when exposed to a combination of ultraviolet and visible light. The photo-induced motion mimics the oscillatory behavior of biological flagella and enables propagation of microwires across a surface and through liquids, with translational speeds up to 7 μm s-1 . This is the first example of molecular crystals that show complex oscillatory behavior under continuous irradiation. A model that relates the rotation of the transition dipole moment between reversible E→Z photoisomerization to the microscopic torque can qualitatively reproduce how the rotational frequency depends on light intensity and polarization.