Thermo-responsive shape and optical memories of photonic composite films enabled by glassy liquid crystalline polymer networks

Abstract

We propose a novel shape and optical memories of a photonic composite film based on a silica opal photonic crystal (PC) template and a liquid crystal polymer network (LCN). Here, the photonic composite film was fabricated by introducing a LCN precursor into a silica opal PC template, followed by UV photo-polymerization and then by the removal of the template. The obtained bilayer-structure photonic film was found to spontaneously form a three-dimensional (3D) temporary bending shape in response to heating, and thus the corresponding reflection color of the photonic composite film shows a blue shift during bending deformation. The inherent mechanisms of these two observations could be attributed to the variations of the LC molecule orientation and the light reflection in the photonic composite film during the thermal process. More intriguingly, the resulting temporary bending shape was fixed by applying mechanical force during slowly cooling down to the room temperature or autonomously fixed by a rapid cooling in liquid nitrogen. Additionally, this temporary state could restore back to the permanent flat shape when the film is cooled from the heat source without an external force. Finally, more complex 3D shape-memory samples could also be achieved by simply controlling the LC alignment or designing the sample geometry. This work opens up a new way to develop a novel shape-memory polymer photonic film.

Recent advances in colour-tunable soft actuators

“…First, existing colour-tunable soft actuators are still inferior to living creatures, which can sense and react to different stimuli. More functionalities (e.g., stiffness change for protection) 86 are expected to be integrated with colour-tunable soft actuators which could greatly improve their interaction with environments. In addition, soft actuators should react specifically to a single stimulus or multiple stimuli (e.g., on demand alteration of the optical signal or/and actuation and even self-adaptive changes in colour, shape, or stiffness under external stimuli) and fulfil sensing, analysing and actuation multifunctionalities.…”

“…Owing to the excellent stability, high lustre and adjustability of structural colour, structural colour-tunable soft actuators have provided wide application prospects, especially in the fields of soft robotics, wearable electronic devices for visible environmental detection and health monitoring. 33,34,60,64,65,69,[84][85][86][87][88][89] Notably, structural colour-tunable soft actuators can realize reversible and irreversible colour changes via employing different polymer matrices. For example, introducing reversible (liquid crystal elastomers, 34,63,86 hydrogels 65,69 ) or irreversible (shape memory polymers 90,91 ) stimuli-responsive polymers into the periodic micro/nano structures of the structural colour-tunable soft actuators can simultaneously tune the lattice parameters during the reversible or irreversible deformation processes.…”

“…6B and C). 63 Such structural colour-tunable soft actuators provide the possibilities of environmental temperature detection, thermal camouflage skin, 97 photonic shape-memory polymer film, 86 and energy harvesting.…”

A NIR light-triggered pyroelectric-dominated generator based on a liquid crystal elastomer composite actuator for photoelectric conversion and self-powered sensing

“…This bending mechanism is similar to that of SWNT-LCE composite/silicone bilayer and quasi-bilayer LCEbased composite lms in previous reports. 37,46,47 Fig. 2h shows the variation in the at and bending angles with cycling before and aer exposure to NIR light.…”

Infrared actuation-induced simultaneous reconfiguration of surface color and morphology for soft robotics

“…However, this new strategy for bio-inspired smart films has been underexplored so far in the literature. Recently, Guo, Wei, and coworkers reported thermoresponsive photonic crystal composite actuators, where SiO 2 photonic crystals were embedded in the matrix of excessive LCE or liquid crystalline polymer networks 39 , 40 . Upon exposure to heat using an external heating source, the photonic crystal composite actuators could change the shape as well as the color.…”