Biocompatible Optical Needle Array (BONA) is showing to be a powerful tool complementing the novel antibacterial blue light therapy. BONA is able to deliver light to deeper skin tissue layers successfully as shown in experiments. In this study, we will discuss BONA’s design, mechanical and optical properties, production method, plus propose improvements to optimize it all. A special skin phantom with photosensitizer was developed in order to investigate how light is delivered inside the tissue. The phantom shows the light scattering pattern through photobleach, allowing us to determine length, thickness and spacing between needles. Other quantitative optical properties as penetration depth were determined using a different phantom (using PDMS). Mechanical properties as needle resistance were determined using one axis of a custom biaxial tensile strain device. The results led us to conclude that besides the great results, there is still room for improvements regarding tip sharpness and manufacturing time and cost, which would be solved with the enhanced fabrication method proposed.
When liquid crystals are dispersed in an immiscible fluid, microdroplets of liquid crystal are spontaneously formed in a fraction of a second. They have optically anisotropic internal structure, which is determined by the ordering of liquid crystal molecules at the interface. Spherical droplets of a nematic liquid crystal can function as whispering-gallery-mode microresonators with an unprecedented width of wavelength tunability by an electric field. WGM pulsed lasing in dyedoped nematic microdroplets is sensitive to strain, temperature and presence of molecules that change molecular orientation at the interface. Omnidirectional 3D lasing was demonstrated in droplets of chiral nematic liquid crystals that form 3D Bragg-onion resonators. We present recent progress in this field, including electric tuning of 3D lasing from chiral nematic droplets and self-assembly of ferroelectric smectic-C* microdroplets with the onion-Bragg structure. We show that anisotropic fibres could be self-assembled from smectic liquid crystals.
In this work we show resonant transfer of light from a planar polymer waveguide into a high index solid microsphere
(BaTiO3) or nematic liquid crystal microdroplet. BaTiO3 spheres were deposited on the waveguide
surface either in dry form or as dispersion in pure water. On the other hand nematic liquid crystal (NLC)
droplets were dispersed in a 10 mM sodium dodecyl sulfate (SDS) in water that promoted perpendicular surface
anchoring of 5CB and therefore radial droplet configuration. Planar waveguides were produced by spinning a
high refractive index polymer (1.68 at 632 nm) onto a soda lime glass. We used two different sources of light,
either 671 nm diode laser or the supercontinuum (SC) laser for the mode launching into the thin film waveguide
using a prism film coupler. The resonant tunneling of light from the waveguide into the high index spheres and
LC microcavities was observed in the case of SC illumination, because the spectrum of light radiated from the
both microcavities clearly showed whispering gallery modes.
In this work we show that nematic liquid-crystal droplets can be used as low-loss and highly tunable whisperinggallery
mode (WGM) optical microcavities. They are spontaneously formed by mixing the liquid crystal with an
immiscible liquid. The optical modes can be tuned either by applying an electric field, changing the temperature
or by mechanical deformation. The tuning range for the electric field is as high as 20 nm at 2.6 V/μm for a ~ 600
nm WGM in 17 μm diameter droplets. Tuning is fast and almost linear with the applied voltage. In the case of
the temperature tuning, we can shift the modes by more than 15 nm at a temperature change of 30 K. Further,
we can also apply mechanical deformation to a free standing film of PDMS polymer containing the liquid crystal
droplets. At 15% strain the mode shift is more than 30 nm. In all the three cases the tuning exceeds the free
spectral range of the resonators and is completely reversible.
The interactions between different types of colloidal particles are measured and analyzed. We use these interactions to
build different self-assembled microstructures, such as dimers, chains, wires, crystals and superstructures. In the
experiments we have used different size, different symmetry of colloids (elastic dipoles and quadrupoles) and different
way of colloidal binding (via localized defects and via entangled defects). We use optical tweezers for directed selfassembly
of colloidal particles. Special attention is devoted to the hierarchical superstructures of large and small
particles. We show that smaller, submicron colloidal particles are trapped into the topological defect rings or loops,
twisting around larger colloidal particles, which are sources of strong nematic deformations. Various possible
applications are discussed, especially in photonics and metamaterials.