Laser treatment of ITO thin films with Carbon Nanotubes for Liquid Crystal Devices

In this paper, the influence of laser ablation on the refractive properties of indium tin oxides (ITO) thin films with deposited single-wall Carbon Nanotubes (CNTs) was considered. Sputtering of CNTs was preliminary based on the laser-oriented method with application of the external electric field. The laser ablation of ITO-CNTs coatings allows changing the electric, optical and mechanical properties dramatically. Moreover, this technical operation permit to switch the topology of the surface, thus it leads to the conversion of the refractive index. The possibility of index-matching due to the laser treatment contributes to the expansion of the technical capabilities of LC devices.

Three-dimensional morphology of bacterial community developed on the index-matched materials

Herein, we demonstrate that the use of index-matching materials (IMMs) allows direct visualization of microbial cells maintained at a solid–liquid interface through confocal reflection microscopy (CRM). The refractive index mismatch induces a background reflection at the solid–liquid interface that dwarfs the reflection signals from the cells and results in low-contrast images. We found that the IMMs sufficiently suppressed the background reflection at the solid–liquid interface, facilitating the imaging of microbes at the solid surface using CRM. The use of IMMs allowed quantitative analysis of the morphology of the mesh-like structure of Pseudomonas aeruginosa biofilms formed under denitrifying conditions, which led us to propose a novel structural model of the highly porous biofilm structure. These results indicate that the use of CRM coupled with an IMM offers a unique and promising tool for probing the dynamics of biofilm formation, along with visualization of environmental organisms and newly isolated bacteria, for which transformation methods are difficult to establish.

Refractive-index matching enhanced polarization-sensitive optical coherence tomography quantification in human brain tissue

The importance of polarization-sensitive optical coherence tomography (PS-OCT) has been increasingly recognized in human brain imaging. Despite the recent progress of PS-OCT in revealing white matter architecture and orientation, quantification of fine-scale fiber tracts in the human brain cortex has been a challenging problem, due to a low birefringence in the gray matter. In this study, we investigated the effect of refractive index matching by 2,2'-thiodiethanol (TDE) immersion on the improvement of PS-OCT measurements in ex vivo human brain tissue. We obtain the cortical fiber orientation maps in the gray matter, which reveals the radial fibers in the gyrus, the U-fibers along the sulcus, as well as distinct layers of fiber axes exhibiting laminar organization. Further analysis shows that index matching reduces the noise in axis orientation measurements by 56% and 39%, in white and gray matter, respectively. Index matching also enables precise measurements of apparent birefringence, which was underestimated in the white matter by 82% but overestimated in the gray matter by 16% prior to TDE immersion. Mathematical simulations show that the improvements are primarily attributed to the reduction in the tissue scattering coefficient, leading to an enhanced signal-to-noise ratio in deeper tissue regions, which could not be achieved by conventional noise reduction methods.

Bioinspired Microstructured Polymer Surfaces with Antireflective Properties

Over the years, different approaches to obtaining antireflective surfaces have been explored, such as using index-matching, interference, or micro- and nanostructures. Structural super black colors are ubiquitous in nature, and biomimicry thus constitutes an interesting way to develop antireflective surfaces. Moth-eye nanostructures, for example, are well known and have been successfully replicated using micro- and nanofabrication. However, other animal species, such as birds of paradise and peacock spiders, have evolved to display larger structures with antireflective features. In peacock spiders, the antireflective properties of their super black patches arise from relatively simple microstructures with lens-like shapes organized in tightly packed hexagonal arrays, which makes them a good candidate for cheap mass replication techniques. In this paper, we present the fabrication and characterization of antireflective microarrays inspired by the peacock spider’s super black structures encountered in nature. Firstly, different microarrays 3D models are generated from a surface equation. Secondly, the arrays are fabricated in a polyacrylate resin by super-resolution 3D printing using two-photon polymerization. Thirdly, the resulting structures are inspected using a scanning electron microscope. Finally, the reflectance and transmittance of the printed structures are characterized at normal incidence with a dedicated optical setup. The bioinspired microlens arrays display excellent antireflective properties, with a measured reflectance as low as 0.042 ± 0.004% for normal incidence, a wavelength of 550 nm, and a collection angle of 14.5°. These values were obtained using a tightly-packed array of slightly pyramidal lenses with a radius of 5 µm and a height of 10 µm.

FACT For Fast And Three-Dimensional Imaging of Intact Tissues

Free of Acrylamide Sodium Fast Free-of-Acrylamide Clearing Tissue (FACT) is a developed technique using no acrylamide for clearing tissues. As the lipid removal normally is a harmful process and it causes loss of biological molecules such as proteins and on the other hand is crucial for transparency and efficient antibody staining throughout the whole tissue especially for microscopy and imaging, the FACT technique is suitable since it makes chemical bonding of membrane and intracellular proteins with the extracellular matrix creating a massive three-dimensional (3D) matrix and structural support to fortify the tissue during processing. Compared to other acrylamide-based techniques, FACT requires less labor, toxic, and harmful chemicals. Here we describe protocols encompassing every angle and dimension of the FACT protocol for antibody staining and imaging of whole-cleared tissues while preserving the structure and increasing the image quality. The entire protocol includes tissue perfusion, fixation, clearing, antibody staining, Refractive Index Matching (RIM), microscopy, and imaging; this timing varies due to the size, weight, different kind of tissues and the type of immunostaining. This technique has been favorably performed on different types of tissues for molecular interrogation analysis of large tissues.