Photocontrolled Translational Motion of a Microscale Solid Object on Azobenzene‐Doped Liquid‐Crystalline Films

Abstract

On the move: Irradiation of azobenzene-doped liquid crystalline films with UV/Vis light results in the photocontrolled translational motion of microscale solid object on the surface, which occurs through cis-trans isomerization of the azobenzene unit. Irradiation with an Ar(+) laser (488 nm) resulted in precise control of the translational motion so that the particle always moved away from the irradiation position (see picture).

Light-induced Phase Transition of Lyotropic Liquid Crystals and Motion Behavior of Micron Objects via Photochemical Azobenzene Molecules

“…However, as shown in Fig.4 (b), when the Az-doped samples were irradiated with Ar+ laser, the samples lost their birefringence, so the phase transition from N to I state was induced. Similar experiment conducted in our previous work [6,7,12] explained the mechanism of phase transition by Ar+ laser irradiation in terms of order-disrupting molecules Az through conformational changes. That means the phase transition can be induced in an Az-doped-LLC system in which Ar+ laser exposure directly decreased the order of the mixture through trans-cis-trans cycle photoisomerization of Az moiety.…”

“…Similarly, the gradient in surface tension can also be used to control the motion of glass rods in Az-doped polyethylene glycol films, as found by Su Ma et al [10]. However, Lohn, et al described the micron objects can be assembled by thermos-induced phase transition [2], whose driving force is also accorded with our previous work [6][7]12].…”

“…Owing to the photo-isomerization behavior, much effort has been focused on the Az compounds to control phase transition of LCs as well as alignment of LCs for applications on optical displays and assembly technology, which have been studied by various external stimuli, such as gravitational field, external electric, magnetic fields, thermo, and light [1][2][3][4][5][6][7][8].…”

Photocontrollable Liquid‐Crystalline Actuators

“…Kurihara et al presented the fi rst observation of controlled translational motion of polystyrene (PS) microparticles on the surface of LC fi lms, which is driven entirely by light. [ 164 ] Okano et al proposed photoinduced expansion and condensation behavior in pure AZ LMWLCs on the surface of water. [ 165 ] The photochemical processes of those AZ LMWLCs with room-temperature LC phases were regarded as the driven force for the light-induced deformation.…”

Photoresponsive Cholesteric Liquid Crystals

“…A major challenge is not only to control the mechanical motion of molecules by light, but also to transform such motion into a macroscopic change in a system. In recent years, some synthetic molecular systems have been developed for the creation of light-induced mechanical motions in LC media including low molecular weight LCs, LC polymers, and LC elastomers [137,138].…”