Optical Wavelength Selective Photoactuation of Nanometal-Doped Liquid Crystalline Elastomers by Using Surface Plasmon Resonance

Abstract

Photoactuated liquid crystalline elastomer (LCE) materials are gaining much attention in many application fields, but challenges for the precise modulation of their photoresponses still exist. Researchers have explored various optical parameters, such as polarization, intensity, and wavelength, to obtain differential responses. The development of photoactuated LCE materials with wavelength-selective responsiveness is more versatile and has attracted more interest, but such LCE materials are commonly prepared by incorporating different molecular chromophores or dyes into the LCE matrices. When the surface plasmon resonance (SPR) characteristic of nanometals, which can generate strong photothermal conversion, and the difference of SPR absorption wavelength bands of different nanometals are considered, a strategy of constructing wavelength-selective actuation of LCE materials by using the SPR photothermal effect can be demonstrated, as done herein. The LCE nanocomposites doped by nanogold or nanosilver were fabricated and exhibited good SPR absorption but in different wavelength bands of the visible spectrum range. They had strong actuation under light irradiation with the wavelengths being inside their respective absorption band but could not be effectively actuated by the light beyond their respective absorption band. A smart electronic device, implementing a hierarchical structured LCE nanocomposite doped by nanogold and nanosilver in different domains as the two-switch actuator, was prepared and capable of outputting different signals in response to the different wavelength bands filtered from a light source, which released the actuator from the restriction of light scanning direction or position. Our work provides new insights for the convenient and precise photoactuation of the LCE actuators.

Control Strategies for Soft Robot Systems

“…[314] One manifestation of this concept uses the wavelength selectivity of plasmon resonance of nanometals. [315,316] Also, dye-doped LCEs [317] and LCEs doped with single-wall carbon nanotube (SWCNT) can achieve a similar function. [318] Because such materials are easy to assemble together, one mechanism can be fabricated with several independent parts that can only be actuated in a certain wavelength bandwidth.…”

Rapidly responsive liquid metal/polyimide photothermal actuators designed based on the bilayer structure difference in coefficient of thermal expansion

“…In contrast, metallic photothermal fillers such as gold nanocrystals are well dispersed and isolated, and small amounts filled into the matrix can avoid long distance heat transfer and can achieve local photoactuation, showing the advantages of high spatial resolution of photoactuation. 2,11 Ivan I. Smalyukh's group 12 filled gold nanocrystals into liquid crystal elastomers, and the heat generated by the gold nanocrystals under the laser beam was locally transferred to the microparticles of the submicron region, which provides photothermal control of the ordering in the liquid crystal elastomer, resulting in reversible and irreversible shape changes.…”

Optical wavelength selective actuation of dye doped liquid crystalline elastomers by quasi-daylight

“…They are characterized by the combination of LC orientational ordering and the rubbery elasticity of polymer networks, which creates unique properties, such as self-organization, active stimuliresponse, reversible phase transition, reversible and large anisotropic shape change under the imposed external stimuli, programmable morphing performance, etc. [1][2][3][4][5][6] These fascinating properties together with the other advantages, such as low weight, tailorable softness of the material, better compatibility with biologic tissues, etc., make the LCE materials an excellent candidate for a wide range of applications, such as smart actuators, [7][8][9][10][11][12][13][14][15][16][17][18][19] artificial muscles, [20][21][22][23][24][25][26] soft robots, [27][28][29][30][31][32][33][34] biomimetic devices, [35][36][37][38][39][40][41][42][43][44] etc.…”

“…The thermal actuation of LCE materials can be transformed into light actuation by the photothermal effect. LCEs can be incorporated with a variety of photothermal agents, such as carbon nanomaterials, 15,16,[55][56][57][58][59] nano metals, [60][61][62][63][64][65][66] conjugated polymer particles, 67 organic dyes, 10,39,46,[68][69][70] etc. They can absorb visible or near infrared light and convert light energy into thermal energy to drive the shape change of LCE materials through releasing heat into matrices.…”

“…1–6 These fascinating properties together with the other advantages, such as low weight, tailorable softness of the material, better compatibility with biologic tissues, etc. , make the LCE materials an excellent candidate for a wide range of applications, such as smart actuators, 7–19 artificial muscles, 20–26 soft robots, 27–34 biomimetic devices, 35–44 etc.…”