Compact Incoherent Multidimensional Imaging Systems Using Static Diffractive Coded Apertures

Incoherent holographic imaging technologies, in general, involve multiple optical components for beam splitting—combining and shaping—and in most cases, require an active optical device such as a spatial light modulator (SLM) for generating multiple phase-shifted holograms in time. The above requirements made the realization of holography-based products expensive, heavy, large, and slow. To successfully transfer the holography capabilities discussed in research articles to products, it is necessary to find methods to simplify holography architectures. In this book chapter, two important incoherent holography techniques, namely interference-based Fresnel incoherent correlation holography (FINCH) and interferenceless coded aperture correlation holography (I-COACH), have been successfully simplified in space and time using advanced manufacturing methods and nonlinear reconstruction, respectively. Both techniques have been realized in compact optical architectures using a single static diffractive optical element manufactured using lithography technologies. Randomly multiplexed diffractive lenses were manufactured using electron beam lithography for FINCH. A quasi-random lens and a mask containing a quasi-random array of pinholes were manufactured using electron beam lithography and photolithography, respectively, for I-COACH. In both cases, the compactification has been achieved without sacrificing the performances. The design, fabrication, and experiments of FINCH and I-COACH with static diffractive optical elements are presented in details

Localization of nanospheres in pheochromocytoma-like cells following exposure to high-frequency electromagnetic fields at 18 GHz

Exposure to high-frequency (HF) electromagnetic fields (EMFs) at 18 GHz was previously found to induce reversible cell permeabilization in eukaryotic cells; however, the fate of internalized foreign objects inside the cell remains unclear. Here, silica core-shell gold nanospheres (Au NS) of 20 ± 5 nm diameter were used to study the localization of Au NS in pheochromocytoma (PC 12) cells after exposure to HF EMFs at 18 GHz. Internalization of Au NS was confirmed using fluorescence microscopy and transmission electron microscopy. Analysis based on corresponding scanning transmission electron microscopy energy-dispersive spectroscopy revealed the presence of the Au NS free within the PC 12 cell membrane, cytoplasm, enclosed within intracellular vesicles and sequestered in vacuoles. The results obtained in this work highlight that exposure to HF EMFs could be used as an efficient technique with potential for effective delivery of drugs, genetic material, and nanomaterials into cells for the purpose of cellular manipulation or therapy

Comment on “Bactericidal Effects of Natural Nanotopography of Dragonfly Wing on <i>Escherichia coli</i>”

Comment on “Bactericidal Effects of Natural Nanotopography of Dragonfly Wing on <i>Escherichia coli</i>

Enhanced Reconstruction of Spatially Incoherent Digital Holograms Using Synthetic Point Spread Holograms

Coded aperture imaging (CAI) methods offer multidimensional and multispectral imaging capabilities with minimal resources than what is needed in a lens-based direct imager. In the CAI method, the light diffracted from an object is modulated by a coded mask, and the resulting intensity distribution is recorded. Most of the CAI techniques involve two steps: the recording of the point spread function (PSF) and object intensity under identical conditions and with the same coded mask. The image of the object is reconstructed by computationally processing the PSF and object intensity. The above recording and reconstruction procedure precludes the introduction of special beam characteristics in imaging, such as a direct imager. In this study, a postprocessing approach is developed, where synthetic PSFs capable of introducing special beam characteristics when processed with the object intensity are generated using an iterative algorithm. The method is applied to generate edge-enhanced images in both CAI as well as Fresnel incoherent correlation holography methods

Single shot multispectral multidimensional imaging using chaotic waves

Abstract Multispectral imaging technology is a valuable scientific tool for various applications in astronomy, remote sensing, molecular fingerprinting, and fluorescence imaging. In this study, we demonstrate a single camera shot, lensless, interferenceless, motionless, non-scanning, space, spectrum, and time resolved five-dimensional incoherent imaging technique using tailored chaotic waves with quasi-random intensity and phase distributions. Chaotic waves can distinctly encode spatial and spectral information of an object in single self-interference intensity distribution. In this study, a tailored chaotic wave with a nearly pure phase function and lowest correlation noise is generated using a quasi-random array of pinholes. A unique sequence of signal processing techniques is applied to extract all possible spatial and spectral channels with the least entropy. The depth-wavelength reciprocity is exploited to see colour from depth and depth from colour and the physics of beam propagation is exploited to see at one depth by calibrating at another

Direct Measurement of Temperature Diffusivity of Nanocellulose-Doped Biodegradable Composite Films

The thermal properties of novel nanomaterials play a significant role in determining the performance of the material in technological applications. Herein, direct measurement of the temperature diffusivity of nanocellulose-doped starch&ndash;polyurethane nanocomposite films was carried out by the micro-contact method. Polymer films containing up to 2 wt%. of nanocellulose were synthesised by a simple chemical process and are biodegradable. Films of a high optical transmittance T&asymp;80% (for a 200 &mu;m thick film), which were up to 44% crystalline, were characterised. Two different modalities of temperature diffusivity based on (1) a resistance change and (2) micro-thermocouple detected voltage modulation caused by the heat wave, were used for the polymer films with cross sections of &sim;100 &mu;m thickness. Twice different in-plane &alpha;‖ and out-of-plane &alpha;&perp; temperature diffusivities were directly determined with high fidelity: &alpha;‖=2.12&times;10&minus;7 m2/s and &alpha;&perp;=1.13&times;10&minus;7 m2/s. This work provides an example of a direct contact measurement of thermal properties of nanocellulose composite biodegradable polymer films. The thermal diffusivity, which is usually high in strongly interconnected networks and crystals, was investigated for the first time in this polymer nanocomposite

Biomimetic Nanopillar Silicon Surfaces Rupture Fungal Spores

The mechano-bactericidal action of nanostructured surfaces is well-documented; however, synthetic nanostructured surfaces have not yet been explored for their antifungal properties toward filamentous fungal species. In this study, we developed a biomimetic nanostructured surface inspired by dragonfly wings. A high-aspect-ratio nanopillar topography was created on silicon (nano-Si) surfaces using inductively coupled plasma reactive ion etching (ICP RIE). To mimic the superhydrophobic nature of insect wings, the nano-Si was further functionalised with trichloro(1H,1H,2H,2H-perfluorooctyl)silane (PFTS). The viability of Aspergillus brasiliensis spores, in contact with either hydrophobic or hydrophilic nano-Si surfaces, was determined using a combination of standard microbiological assays, confocal laser scanning microscopy (CLSM), and focused ion beam scanning electron microscopy (FIB-SEM). Results indicated the breakdown of the fungal spore membrane upon contact with the hydrophilic nano-Si surfaces. By contrast, hydrophobised nano-Si surfaces prevented the initial attachment of the fungal conidia. Hydrophilic nano-Si surfaces exhibited both antifungal and fungicidal properties toward attached A. brasisiensis spores via a 4-fold reduction of attached spores and approximately 9-fold reduction of viable conidia from initial solution after 24 h compared to their planar Si counterparts. Thus, we reveal, for the first time, the physical rupturing of attaching fungal spores by biomimetic hydrophilic nanostructured surfaces