Autonomous flipping of azobenzene assemblies under light irradiation (II)

Abstract

<p>To create autonomous microrobots which move in the presence of a constant energy source, their mechanical motion must have a capacity for self-control. This is realized when a structural change occurs with conversion of energy facilitated by cofactors, with a self-regulation component to prevent reaching a static state. Here, we present a single crystal structure analysis of azobenene derivatives which reveals a mille-feuille-like layered structure of sparse and dense layers of six independent azobenzene moieties. In this anisotropic structure, a specific azobenzene molecule acts as a reaction center for a light-to-mechanical function process. The other molecules in the crystal act as modulators. Moreover, depending on the photoisomerisation process activated by a polarized light source, different cyclic motions are observed. We clarify the mechanism by which the self-organized mechanical behavior of these azobenzene molecules is achieved at the molecular level. Thus, the present results demonstrate that autonomously driven molecular materials can exhibit information-responsive and self-sustainable motion by incorporating stimulus-responsive sensors. </p>

Self‐Propulsion of a Light‐Powered Microscopic Crystalline Flapper in Water

“…As previously reported, [ 12 ] the crystal showed self‐continuous flipping under continuous irradiation by blue light through a sequence of time‐irreversible processes, in which light‐triggered isomerization of 1 (Steps 1 and 3, in Figure ) induced a crystalline phase transition (Steps 2 and 4) which repeatedly progressed without external control. According to microscopic observation at several magnifications, the flipping direction was inherent in each crystal, and we suspect that the asymmetrical crystal outline and the asymmetrical crystal structure, the space group of which is expected to be P 1 , [ 15 ] determined the bending direction. Due to its limit‐cycle mechanism with morphological change (Figure 2), the crystal stored the received energy and then sharply converted it to mechanical power.…”

“…In the present study, we report the swimming mechanics of tiny self‐flipping crystals in a flat‐box water pool; in our previous work, we focused on the generation and mechanism of macroscopic self‐oscillation [ 12 ] and the investigation of crystalline structure. [ 15 ]…”