Electrothermally driven structural colour based on liquid crystal elastomers

Abstract

In this article, a new type of electrothermally driven photonic crystal based on liquid crystal elastomers (LCEs) was developed, and its optical properties (structural colour) driven by voltage were described. Graphite nanoparticles were spin-coated on glass-substrates and acted as an electrothermal conversion layer, on which the prepared LCE-based inverse opaline films were mounted. When voltage is applied on the fabricated system, the heat produced by the graphite layer will induce the deformation of the coated inverse opaline film and thus the electrothermally driven photonic system or structural colour is realized. We found that realignment behaviour existed when these films were first above their glass transition temperatures (T g ), and during this realignment process, the structural colour of weakly crosslinked inverse opaline films disappeared, probably due to the collapse of the periodically ordered porous structure. The threshold cross-linking density (C x ) for producing LCE-based inverse opalines with reversible response is 25 mol%. Interestingly, it is found that the treatment of the prepared photonic films by using silicone oil could reduce the threshold C x to 15 mol%, and the fabrication of LCE-based inverse opaline with widely tunable optical properties is possible. When the temperature of the used electrothermal conversion layer is close to the nematic-isotropic (N-I) transition temperature (T NI ) of the LCE films, the liquid crystal moieties in inverse opaline structure became isotropic, leading to rapid shift of the Bragg-diffraction peak and corresponding structural colour change. After turning off the voltage, they could regain to the initial state. With the decrease of the cross-linking density of the photonic-structured elastomers, the degree of Bragg-diffraction shift became larger. Remarkably, the response of these films stimulated by electric voltage is fast and the reversibility is perfect.

Electrically responsive photonic crystals: a review

“…This limitation was surpassed by Jiang et al through fabrication of an electrothermally active inverse opal, based on a thermoresponsive liquid crystal elastomer. 108 The response of this material, in terms of matrix expansion/contraction, depends on the temperature which can be 20 modulated via Joule heating by driving an electric current through a conductive graphite layer embedded into the glass support (Fig. 13b).…”

Dual‐Responsive SPMA‐Modified Polymer Photonic Crystals and Their Dynamic Display Patterns

“…Certain wavelengths of light cannot propagate through the photonic bandgap (PBG) . Therefore, PCs have corresponding reflection peaks and can exhibit structural colors due to Bragg's law of diffraction . In recent years, inspired by the features of PCs, many scientists have studied intelligent PC materials with structural colors .…”

Reversible Photo Actuated Bulk Nanocomposite with Nematic Liquid Crystalline Elastomer Matrix

“…changes [4][5][6][7][8]. Owing to their characteristics as soft materials, currently, LCE materials have always been made in the forms with thin thickness, such as films [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24], fibers [25][26][27][28] or applied as surface coating [29]. However, materials with thin thickness have limitations in forming mechanical actuators, and many actuation functions need to be realized using thick materials, such as bulk materials.…”