Switching Chirality in Arrays of Shape‐Reconfigurable Spindle Microparticles

Abstract

The giant circular photo‐galvanic effect is realized in chiral metals when illuminated by circularly polarized light. However, the structure itself is not switchable nor is the crystal chirality in the adjacent chiral domains. Here spindle‐shaped liquid crystalline elastomer microparticles that can switch from prolate to spherical to oblate reversibly upon heating above the nematic to isotropic transition temperature are synthesized. When arranged in a honeycomb lattice, the continuous shape change of the microparticles leads to lattice reconfiguration, from a right‐handed chiral state to an achiral one, then to a left‐handed chiral state, without breaking the translational symmetry. Accordingly, the sign of rotation of the polarized light passing through the lattices changes as measured by time‐domain terahertz spectroscopy. Further, it can locally alter the chirality in the adjacent domains using near‐infrared light illumination. The reconfigurable chiral microarrays will allow us to explore non‐trivial symmetry‐protected transport modes of topological lattices at the light–matter interface. Specifically, the ability to controllably create chiral states at the boundary of the achiral/chiral domains will lead to rich structures emerging from the interplay of symmetry and topology.

Exploiting Molecular Orders at the Interface of Microdroplets for Intelligent Materials

“…LCE microparticles with uniform size are produced via a microfluidic device, where nonreactive mesogenic 5CB and magnetic nanoparticles can be introduced (Figure a). 5CB molecules can coalign with RMs and LCOs inside microdroplets after the removal of organic solvent. , With PVA dispersed in water to offer planar anchoring, the microdroplets are formed with a bipolar configuration, where 5CB lowers the precursor viscosity of the organic phase and improves the surface anchoring strength . After photopolymerization under UV light and the extraction of 5CB by organic solvent ethanol, spindle-shaped LCE microparticles are obtained, as a result of twisting of the director field and anisotropic shrinkage within the particle. , The morphology of the microparticles can be tuned by varying the fraction of 5CB and the molar ratio of LCOs to RMs in the precursors.…”

“…Bottom: enlarged images showing the selected regions that undergo the chirality switch (red boxes) or maintain the original chirality (black boxes). Adapted with permission from ref . Copyright 2023 Wiley-VCH GmbH.…”

“…(c) Photograph of the setup and calculated field strength distribution of the uniform magnetic field and (d) bright-field optical microscopy images showing the reorientation of the microparticles under the magnetic field. Adapted with permission from refs and . Copyrights 2022 and 2023 Wiley-VCH GmbH, respectively.…”

Programming Deformations of 3D Microstructures: Opportunities Enabled by Magnetic Alignment of Liquid Crystalline Elastomers

“…Stretching of a partially cured non-cross-linked sample induces the mesogens to align along the stretching direction, which can be locked-in by a subsequent cross-linking step. Similarly, in 3D printing and microfluidics, , the shear force of the extrusion nozzle aligns mesogens in the produced filament or droplets along the extrusion direction; therefore each printed fiber or droplet (with a typical diameter >100 μm) has the ability to only deform along its geometric axis. 3D printing is, thus, primarily applicable to macroscopic objects, where complex director distribution is obtained by spatially organizing the filaments into a multilayer configuration.…”

“…Stretching of a partially cured non-cross-linked sample induces the mesogens to align along the stretching direction, which can be locked-in by a subsequent cross-linking step. Similarly, in 3D printing and microfluidics, , the shear force of the extrusion nozzle aligns mesogens in the produced filament or droplets along the extrusion direction; therefore each printed fiber or droplet (with a typical diameter >100 μm) has the ability to only deform along its geometric axis. 3D printing is, thus, primarily applicable to macroscopic objects, where complex director distribution is obtained by spatially organizing the filaments into a multilayer configuration. Topographical alignment − makes use of a surface layer patterned either using a photomask, patterned electrodes for electric fields, mechanical rubbing (creating nano- or microgrooves), or inscribed by nanoscribe, to align the material conforming to the surface textures by minimizing LC elastic energy (Figure b, ii.a ).…”