Phototriggered Selective Actuation and Self‐Oscillating in Dual‐Phase Liquid Crystal Photonic Actuators

Abstract

Among different kinds of photoactuators available, those based on liquid‐crystal polymer networks (LCNs) are gathering a great deal of attention due to their fast response and versatility of structural design. However, only a few reports have focused on the phototriggered LCN actuators for complex actuation and multifunction properties. Here, a phototriggered LCN‐based photonic actuator with quasi‐bilayer structure that exhibits fast and reversible shape changes is created by infiltrating a LCN precursor–graphene oxide mixture into a silica opal template, ultraviolet photopolymerization, and removing the template. Particularly, the phototriggered selective actuation behavior is achieved in dual‐phase LCN‐based photonic actuators with macroscopically alternating nematic (N) and isotropic (I) phase, which enables versatile actuation modes and allows multiple shape changes. In addition, a two‐segmented, dual‐phase LCN‐based photonic actuator exhibits self‐oscillating motion when a responsive N‐phase region as localized active point is irradiated, which arises from the self‐shadowing of the passive I‐phase region. To demonstrate the potential application of this self‐oscillating motion behavior, a photoelectric energy conversion device that is capable of converting light energy to electric energy is constructed.

Light‐Responsive Shape‐Changing Polymers

“…Increasing the complexity of LCN‐based actuator systems, Guo and co‐workers demonstrated a light‐driven dual‐phase LC photonic actuator, in which the LCNs were used as a thermal–mechanical component, silica opal was used as a structural color template, and graphene oxide served as a photothermal‐conversion dopant . Selective actuation was achieved by photopatterning, which enabled complex shape changes.…”

“…In a slightly different setup by another group, separate films were prepared from the piezoelectric transducer and from the photoresponsive polymer. The films were then placed close to each other in a way that the bending LCE induced self‐sustained oscillation in the piezo element, generating alternating current (Figure c,d) …”

Shining Light on Liquid Crystal Polymer Networks: Preparing, Reconfiguring, and Driving Soft Actuators

“…Yu and coworkers utilized the continuous oscillation of an azobenzene LCN‐containing bilayer strip to swing the attached induction coils and cut magnetic line of force, thus generating an alternating voltage . Guo and coworkers observed self‐oscillating motion in a dual‐phase LCN where the responsive nematic‐phase region was fixed as active hinge and the passive isotropic‐phase region provided self‐shadowing effect . Integrating this self‐oscillating system with a piezoelectric poly(vinylidene fluoride) film, they demonstrated efficient conversion of light energy to electric energy.…”

Self‐Assembly of Colloidal Particles for Fabrication of Structural Color Materials toward Advanced Intelligent Systems

“…The film could perform the corresponding localized actuation upon infrared (IR) irradiation. Furthermore, to complete more complex and selective actuation, Guo and co‐workers further develop a structural colored bionic hand by coupling inverse opal and graphene oxide (GO) as a thermal–mechanical unit and photothermal conversion component . All‐round actuation modes and the corresponding deformation behaviors result in real hand mimic actions, as shown in Figure .…”

“…f) Series of movement of the bionic hand upon visible light irradiation. Reproduced with permission . Copyright 2018, WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim.…”