The photonic band gap of colloidal crystal films made of polystyrene nanospheres was controlled by dry etching
technology using hyperthermal neutral beam. Vertical deposition technique was applied to prepare colloidal crystal films
with face centered cubic lattice structure using aqueous suspension of monodispersed polystyrene particles. The
pseudogap of these colloidal photonic crystals was tuned by etching the films with neutral beam, which reduces the size
of the constituent polystyrene particles. Isotropic reduction of the particles in collodial crystal films resulted in the blue
shift of stop band of the photonic band gap materials. By changing the etching time, the reflected colors of the dry-etched
colloidal crystals were successfully controlled.
Colloidal dispersion of bimodal particles were self-organized inside water-in-oil emulsion droplets by evaporationdriven
self-assembly method. After droplet shrinkage by heating the complex fluid system, small numbers of
microspheres were packed into minimal second moment clusters, which are partially coated with silica nanospheres,
resulting in the generation of patchy particles. The patchy particles in this study possess potential applications for selfassembly
of non-isotropic particles such as dimmers or tetramers for colloidal photonic crystals with diamond lattice
structures. The composite micro-clusters of amidine polystyrene microspheres and titania nanoparticles were also
generated by evaporation-driven self-assembly to fabricate nonspherical hollow micro-particles made of titania shell.
Stable dispersion of colloidal indium tin oxide nanoparticles was prepared by using indium tin oxide nanopowder,
organic solvent, and suitable dispersants through attrition process. Various comminution parameters during the attrition
step were studied to optimize the process for the stable dispersion of indium tin oxide sol. The transparent and
conductive films were fabricated on glass substrate using the indium tin oxide sol by spin coating process. To obtain
antireflective function, partially hydrolyzed alkyl silicate was deposited as over-coat layer on the pre-fabricated indium
tin oxide film by spin coating technique. This double-layered structure of the nanostructured film was characterized by
measuring the surface resistance and reflectance spectrum in the visible wavelength region. The final film structure was
enough to satisfy the TCO regulations for EMI shielding purposes.
The waveguides and light sources are essential building blocks in optofluidics. Here, we have developed the new
approach to fabricate efficient waveguides and light sources by using two-phase stratified flow of dye containing liquid
and air. The liquid-core/air-cladding (LA) waveguide can overcome some of major drawbacks of the liquid-core/liquid-cladding
(L2) waveguide without losing its unique advantages. Specifically, stronger optical confinement, originated
from the large refractive index contrast between core and cladding, enable us to achieve lower propagation losses and
larger captured fractions (the amount of light to be coupled into the liquid core). In addition, the LA waveguides are free
from diffusional mixing of the core and cladding fluids. The fluorescent LA waveguides can be fabricated by
conventional poly(dimethylsiloxane) (PDMS) based soft lithography, which is compatible with the other parts of
optofluidic devices. Therefore, the fluorescent LA waveguide can be easily integrated with precise alignment as an
internal light source of optofluidic devices.
Biomolecular detection using Localized Surface Plasmon Resonances (LSPR) has been extensively investigated
because these techniques enable label-free detection. The high-density metal nanopatterns with tunable LSPR
characteristics have been used as refractive index sensing because LSPR property is highly sensitive to refractive index
change of surroundings. Meanwhile, Colloidal lithography is a robust method for fabricating regularly ordered
nanostructures in a controlled and reproducible way using spontaneous assembly of colloidal particles. In this study,
nanopatterns on UV-curable polymer were prepared via colloidal lithography. Then, metallic nanograil arrays with high
density were fabricated by sputtering noble metals such as gold and subsequent removal of residual polymers and
colloidal particles. From Finite-Difference Time-Domain Method (FDTD) simulations and reflectance spectra, we found
that multiple dipolar plasmon modes were induced by gold nanograil arrays and each mode was closely related with
structural parameters. LSPR characteristics of gold nanograil arrays could be tuned by varying the fabrication conditions
to obtain optimal structures for LSPR sensing. Sensing behavior of gold nanograil arrays was tested by applying various
solvents with different refractive indices and measuring the variations of LSPR dips. Finally, gold nanograil arrays as
LSPR sensors were integrated in optofluidic devices and used to achieve real-time label-free monitoring of biomolecules.
Holographic lithography provides a highly compatible and facile way to fabricate multi-dimensional periodic
nanostructures. Periodic nanostructures have useful applications not only as biological substrates or catalytic supports
but also as nanophotonic devices with various photonic properties such as photonic band-gap (PBG), localized surface
plasmon resonance (LSPR) or surface enhanced Raman scattering (SERS). In combination with single refracting prism
holographic lithography and conventional photolithography, we could achieve the micrometer-scale patterns of periodic
nanostructures which can be integrated in microfluidic chip. With the help of conventional MEMS technologies, Arrays
of pyramid shape and top-cut pyramid shape microprism can be prepared. Single laser exposure step through the
microprism arrays (MPAs) can be generate multiscale patterns of 2D and 3D nanostructures. As prepared nanostructures
combined with microfluidic chip is a highly efficient optofluidic platform which is applicable to the chemical and biosensors.
We propose and demonstrate a new type of a photonic crystal nanolaser integrated into a microfluidic chip, which
is fabricated by multilayer soft lithography. Experimentally, continuous-wave operation of the lasing action has
been observed owing to efficient water-cooling. Characteristics of wavelength tuning by the fluid are investigated
using both theory and experiment. In addition, we propose that dynamic modulation of far-field radiation
pattern can be achieved by introducing a bottom reflector and by flowing the fluid on it. Especially, by choosing
effective one-wavelength distance between the reflector and the cavity, efficient unidirectional emission can be
obtained.
Holographic lithography is one of the promising techniques that can create three-dimensional (3D) periodic
nanostructures without extensive lithography and etching steps. This proceeding discusses novel hybrid lithographic
methods based on the holographic lithography in conjunction with photolithography to generate hierarchically-patterned
structures. Using various types of photoresists including positive, negative and hydrogel, we fabricated 3D nanopatterns
by holographic lithography. Then, two-dimensional (2D) photolithography was combined to pattern the 3D structures.
Eventually, we created a microfluidic channel with 3D periodic patterns. Since the 3D structure possess photonic
bandgap properties as well as interconnected pore networks, this kind of microfluidic channel can be applied to optical
sensors, mixers and filters.
Diamond-like silicon photonic crystals were fabricated by sequential chemical vapor deposition of silica and silicon on
polymer templates photopatterned by holographic lithography. The optical properties of the 3D crystals after each
processing step were measured and compared to the corresponding bandgap simulation. The core-shell morphology
formed during CVD process is approximated using two level surfaces.
In this paper, we report a fast and facile method for fabricating colloidal photonic crystals inside microchannels of radially symmetric microfluidic chips. As the suspension of monodisperse silica or polystyrene latex spheres was driven to flow through the channels under the centrifugal force, the colloidal spheres were quickly assembled into face centered cubic arrangement which had photonic stop bands. The optical reflectance spectrum was modulated by the refractive-index mismatch between the colloidal particles and the solvent filled in the interstices between the particles. Therefore, the present microfluidic chips with built-in colloidal photonic crystals can be used as in-situ optofluidic microsensors for high throughput screening, light filters and biosensors in integrated adaptive optical devices.
In this paper, we report a fast and facile method for fabricating colloidal photonic crystals inside microchannels of
radially symmetric microfluidic chips. As the suspension of monodisperse silica or polystyrene latex spheres was driven
to flow through the channels under the centrifugal force, the colloidal spheres were quickly assembled into face centered
cubic arrangement which had photonic stop bands. The optical reflectance spectrum was modulated by the refractiveindex
mismatch between the colloidal particles and the solvent filled in the interstices between the particles. Therefore,
the present microfluidic chips with built-in colloidal photonic crystals can be used as in-situ optofluidic microsensors for
high throughput screening, light filters and biosensors in integrated adaptive optical devices.
We fabricated two-dimensional (2D) polymeric photonic crystals with atoms stretched along a specific direction by using a double exposure with phase modulation.
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