Solid chiral microspheres with unique and multifunctional optical properties are produced from cholesteric liquid crystal-water emulsions using photopolymerization processes. These self-organizing microspheres exhibit different internal configurations of helicoidal structures with radial, conical or cylindrical geometries, depending on the physicochemical characteristics of the precursor liquid crystal emulsion.

Chirality is one of the most prominent and intriguing aspects of nature, from spiral galaxies down to aminoacids. Despite the wide range of living and non-living, natural and artificial chiral systems at different scales, the origin of chirality-induced phenomena is often puzzling. Here we assess the onset of chiral optomechanics, exploiting the control of the interaction between chiral entities. We perform an experimental and theoretical investigation of the simultaneous optical trapping and rotation of spherulite-like chiral microparticles. Due to their shell structure (Bragg dielectric resonator), the microparticles function as omnidirectional chiral mirrors yielding highly polarization-dependent optomechanical effects. The coupling of linear and angular momentum, mediated by the optical polarization and the microparticles chiral reflectance, allows for fine tuning of chirality-induced optical forces and torques. This offers tools for optomechanics, optical sorting and sensing and optofluidics.

In this letter, we report the results of phototunable lasing in dye-doped cholesteric liquid crystals (DD–CLC). Photoexcitation of DD–CLC films gives rise to laser emission in the violet-UV range. Control of the structure of the chiral dopant driven by UV phototransformation is exploited in order to obtain a permanent variation of the cholesteric pitch. Laser emission wavelength tuning, by means of photoinduced shifting of the selective reflection band of the cholesteric liquid crystals is established. A tuning interval of about 35 nm, in the wavelength range of 385–415 nm, is observed.

Lateral optical forces induced by linearly polarized laser beams have been predicted to deflect dipolar particles with opposite chiralities toward opposite transversal directions. These "chirality-dependent" forces can offer new possibilities for passive all-optical enantioselective sorting of chiral particles, which is essential to the nanoscience and drug industries. However, previous chiral sorting experiments focused on large particles with diameters in the geometrical-optics regime. Here, we demonstrate, for the first time, the robust sorting of Mie (size~wavelength) chiral particles with different handedness at an air-water interface using optical lateral forces induced by a single linearly polarized laser beam. The nontrivial physical interactions underlying these chirality-dependent forces distinctly differ from those predicted for dipolar or geometrical-optics particles. The lateral forces emerge from a complex interplay between the light polarization, lateral momentum enhancement, and out-of-plane light refraction at the particle-water interface. The sign of the lateral force could be reversed by changing the particle size, incident angle, and polarization of the obliquely incident light.

tial for applications such as anisotropic building blocks for the preparation of colloidal crystals and photonic materials of unusual symmetry, colloidal liquid crystals, and biosensors.In summary, we have used a gel trapping technique as a generic method for preparing Janus particles by templating of particle monolayers at air±water or oil±water interfaces, followed by lifting off the particles with PDMS and subsequent deposition of gold. By replication of colloidal monolayers of repulsive particles at liquid surfaces we have also fabricated microporous surfaces and composite supraparticles. ExperimentalIn a typical procedure for the preparation of microporous surfaces or Janus particles, 30 lL of a latex particle suspension/isopropanol solution (50:50) was injected at the interface between a hot Gellan solution at 50 C (prepared by hydration of 2 % Gellan (Kelcogel, CPKelco, UK) in water at 95 C for 10 min) and a pre-warmed decane phase. After setting the gel at 25 C, the decane phase was replaced with PDMS (Sylgard 184, Dow Corning) and cured for 48 h. Then the solid elastomer was peeled off the gel and washed in hot water (95 C) for 10 min to remove Gellan residues from the surfaces. To fabricate PDMS with a microporous surface, the particles were removed by stretching the elastomer and collecting the released particles with a metal blade from the surface in the presence of a surfactant solution (1 mM C 12 E 5 ). Janus particles were produced by gold sputtering (NanoTech Seprep II Sputter coater) on the partially embedded particle monolayer on PDMS and subsequent mechanical removal of the particles from the interface.