Reversible and Rapid Laser Actuation of Liquid Crystalline Elastomer Micropillars with Inclusion of Gold Nanoparticles

Abstract

It is highly desirable for liquid crystal elastomer (LCE) based microactuators to activate and actuate in a highly controlled fashion without perturbing the surrounding environment. To reach this goal, in this study, a novel experimental protocol is developed to successfully incorporate gold nanosphere (AuNS) and gold nanorod (AuNR) into polyacrylate based LCE elastomer to fabricate LCE/AuNR and LCE/AuNS micropillars or microactuators. The effect of gold nanoparticle inclusion has been studied by spectroscopy (UVvis-near-infrared), microscopy (transmission electron microscopy), thermal analysis (differential scanning calorimetry and thermogravimetric analysis), and x-ray scattering (wide-angle x-ray scattering and small-angle x-ray scattering). Finite element analysis is performed to examine the feasibility of utilizing the photothermal effect of AuNR/AuNS to enable photothermal actuation of LCE/AuNR and LCE/AuNS micropillars. The comparative experimental studies on the thermal and photothermal actuation behavior of the LCE, LCE/AuNS, and LCE/AuNR micropillar suggested that AuNR is an excellent candidate for developing high-performance LCE actuators with photothermal actuation capability. With inclusion of less than 1 wt% of AuNR, the very high maximum actuation strain (30%) and rapid response (a few seconds) have been achieved in LCE/AuNR micropillar actuators under 635 nm laser irradiation.

Liquid crystal elastomer actuators: Synthesis, alignment, and applications

“…Gold nanoparticle (AuNP) based LCE composites exhibit enhanced photothermal effects due to localized surface plasmon resonance of the particle . Liu et al developed a fabrication method to incorporate gold nanospheres (AuNS) and gold nanorods (AuNR) into polyacrylate‐based LCEs for a highly controllable microactuator that can be activated without an ambient temperature change . In this study, incorporation of less than 1 wt % of AuNR into LCE micropillar actuators can lead to a maximum 30% actuation strain on irradiation with a 635 nm laser.…”

“…Metallic nanomaterials exhibit a wide range of tunable stimuli‐responsive behaviors and have been incorporated into a number of polymer matrices, including LCEs . Gold nanoparticle (AuNP) based LCE composites exhibit enhanced photothermal effects due to localized surface plasmon resonance of the particle . Liu et al developed a fabrication method to incorporate gold nanospheres (AuNS) and gold nanorods (AuNR) into polyacrylate‐based LCEs for a highly controllable microactuator that can be activated without an ambient temperature change .…”

“…This mixture was melted and filled in to a mold in the isotropic state. Subsequent cooling of the sample to 55 °C under a permanent magnet allowed the sample mixture to align, at which time the sample was polymerized under UV‐light to obtain the LCE composite . Sun et al demonstrated that gold nanocrystals in LCE microparticles could be fabricated using a soft lithographic molding technique .…”

Liquid‐Crystalline Elastomers with Gold Nanoparticle Cross‐Linkers

“…[5] Recently, new hybrid materials obtained by incorporationo fi norganic nanoparticles into polymers were synthesized and studied. [8] Enhanced photothermal actuation behavior of hybrid LCEs with inclusion of less than 1wt% gold nanorodsh as been shown. Nanoparticle-dopedL CEs can have fasterr esponse and better control over the actuation, and overcoming the problemo fl ow thermalc onductivity of LCEs opensacontactless stimulation pathway to induce the anisotropic-isotropic transition by local heating.…”

Photoresponsive Actuators Built from Carbon‐Based Soft Materials

“…Manipulating structure–property correlations has always been a popular research topic in smart materials science. Inspired by natural smart systems, responsive mechanical motions, shape deformation and changes in appearance under various external stimuli (electric, heat, light, humidity, solvent, and magnetism) play essential roles in energy conversion and use . Considerable efforts have been devoted to materials design for developing fast, responsive and large deflection actuators along with efficient energy conversion.…”