RESUMO
Liquid crystal polymers are a special class of soft materials that can change their shape in response to numerous stimuli such as light, heat, electric field, and chemicals. The ability to tailor the deformed shape by tuning the alignment of mesogens across the film has enabled the researchers to generate unique motions from these liquid crystal polymer thin films. Simulating such motions might allow us to understand the underlying mechanisms better and could lead to novel designs. In this paper, we analyze the kinematics of the light-driven rolling motion of wheels fabricated with azobenzene-doped glassy liquid crystal networks through a one-way coupled transient photo-mechanical model. The influence of the isomerization parameters and the alignment of mesogens through the thickness on the kinematics of the wheel is presented. The developed model is further used to assess the feasibility of a light-actuated four-wheeled cart with wheels made of azobenzene-doped liquid crystal network thin films.
RESUMO
Achieving oscillatory motion in polymers without requiring on/off switching of stimuli is a current challenge. Hereby, a free-standing liquid crystal polymer (LCP) is demonstrated to undergo a sustained oscillatory motion when triggered by light, moving back and forth, resembling the motion of a rocking-chair. Two polymer films having different azobenzene photo-switches have been studied, revealing photoswitch requirements as well as illumination conditions necessary to sustain oscillations. The motion presented here shows how feedback loops involving light-triggered actuation, self-shadowing and a shifting center of gravity can be utilized to achieve self-sustained motion in free-standing polymers.