Dunaliella salina algae are trapped and studied using dual-fiber optical tweezers based on nano-imprinted Fresnel lenses. Different forms of cyclic motion of living algae inside the optical trap are observed and analyzed. A characteristic periodic motion in the 0-35 Hz frequency region reflects the algal flagella activity and is used to estimate the algal vitality, by photomovement. The trap stiffness and optical forces are measured for the case of a dead algal cell. It is shown that the dual-fiber optical tweezers can be used to study the vitality (or viability) property of single cells, a property that is essential and can be scaled up to other applications, such as sperm analysis for fertility tests.

NaYF 4 : Eu nanorods with high aspect ratios are elaborated and optically trapped using dual fiber optical tweezers in a counterpropagating geometry. High trapping efficiency is observed using converging beams, emitted from diffractive Fresnel lenses directly 3D printed onto cleaved fiber facets. Stable nanorod trapping and alignment are reported for a fiber-to-fiber distance of 200 μm and light powers down to 10 mW. Trapping of nanorod clusters containing one to three nanorods and the coupling of nanorod motion in both axial and transverse directions are considered and discussed. The europium emission is studied by polarization-resolved spectroscopy with particular emphasis on the magnetic and electric dipole transitions. The respective σ and π orientations of the different emission lines are determined. The angles with respect to the nanorod axes of the corresponding magnetic and electric dipoles are calculated. Mono-exponential emission decay with decay time of 4–5 ms is reported. It is shown that the nanorod orientation can be determined by purely spectroscopic means.

Nanotechnology is being used in different aspects of life to solve different problems. Highway researchers and practitioner are also using nano-materials to modify asphalt binders. Studies associated with the use of nano-materials in pavement construction are still very limited. In order to make this more applicable in the field, there is a need of more studies on this topic. The current study investigates the influence of the nano-based chemical warm mix additive zycotherm on the characteristics of asphalt mixes. In the study zycotherm was added into the mix in different proportions and the properties of the asphalt mixes were examined. In order to assess the moisture damage resistance of the mix, parameters like retained marshall stability (RMS) and tensile strength ratio (TSR) were calculated. Based on the results of these tests, comparisons are made and conclusions are presented in this paper.

We demonstrate optical trapping of rare earth-doped NaYF 4 :Er/Yb nanorods of high aspect ratio (length 1.47 μ m and diameter 140 nm) using a quasi Bessel beam (QBB) generated by positive axicon optical fiber tips. Propulsion or trapping of the nanorods is demonstrated using either single or dual fiber nano-tip geometries. The optical force exerted on the trapped nanorods, their velocities, and their positions have been analyzed. We determine the trap stiffness for a single nanorod to be 0.12 pN/ μ m (0.003 pN/ μ m) by power spectrum analysis and 0.13 pN/ μ m (0.015 pN/ μ m) by Boltzmann statistics in the direction perpendicular to (along) the fiber axes for an average optical power of 34 mW. The experiments illustrate the advantage of using a QBB for multiple nanorod trapping over a large distance of up to 30 μ m.

Optical trapping is the science of holding and immobilizing particles and cells, for further manipulation and spectroscopic studies. Enhancing the application of optical trapping is limited by size and flexibility of this tool, mostly limited to high numerical aperture objectives. In this work, we show the potential of using structured light to further enhance the capabilities of optical fibres as optical tweezers, to be used for applications in which space and throughput are of importance. Using femtosecond two photon direct laser writing, we produce accurately designed micro-optic probes at the tip of optical fibres to enhance the light field for trapping single particles as well as single live cells. Enhanced trapping efficiency, ease of transporting trapped particle, and potential of performing wide spectrum spectroscopy on the trapped entity are the advantages of the present approach.

We report stable and reproducible optical trapping of Eu-doped NaYF4 anisotropic nanorods using single fiber tip optical tweezers for investigating the orientation resolved emission spectra. The nanorods were elaborated by the hydrothermal process followed by annealing and centrifugation steps, resulting in a well-defined size distribution. Nanorod trapping was observed at two positions, first, in fiber tip contact and second, at a finite distance of 4 - 6 µm away from fiber tip in the axial direction. The nanorod trapped with tip contact was highly stable and stay trapped for several hours. They were aligned with the fiber axis with a residual angular distribution width of 4° at a light power of 34.8 mW. Moreover, we have determined trap stiffness of the off-tip trapped nanorod by applying the Boltzmann statistics and power spectra analysis of position fluctuations. Subsequently, the trapped NaYF4:Eu nanorods were used for studying the Eu3+ emission spectra in two orthogonal directions: perpendicular and parallel to the nanorod axis. The influence of anisotropic polarization was observed in the perpendicular direction whereas emission remained isotropic polarization in the parallel direction. The observed emission spectra have been analyzed for the well-defined peaks at 590 and 614 nm corresponds to the magnetic and electric dipole transitions. The experimental investigations were completed by studying the polarization-dependent emission spectra in the perpendicular direction.

Europium-doped NaYF4 nanorods with a high aspect ratio are optically trapped using a single fibre tip optical tweezers. Three distinct trapping positions of the nanorods are observed: in contact with the fibre tip, close to the tip and 5 mu m from the tip end. The direction and polarisation-dependent Eu3+ photoluminescence is investigated by recording the emission parallel and perpendicular to the nanorod long axis through the trapping fibre and the microscope objective, respectively. These spectroscopic measurements permit an unambiguous determination of the nanorod orientation.

A new approach of a highly efficient counter propagating optical fiber based tweezers using 3D printed Fresnel lenses at the fiber facets will be presented. In contrast to conventional fiber tip tweezers the emitted beams of the Fresnel lens fibers are converging resulting in a significantly enhanced trapping efficiency in both axial and transverse direction. The used polymer diffractive Fresnel lens structures are fabricated by femtosecond two photo lithography using a commercial system. The measured trapping efficiencies are found to be up to 90 times higher than for similar results using chemically wet-etched fiber tips. A short outlook on further concepts of enhanced optical fiber tweezers based on 3D diffractive structures will also be given.

An original approach of highly efficient fiber-based optical tweezers using 3D printed diffractive optical elements at an optical fiber facets is presented. As an example Fresnel lens structures, with focal lengths in the range of 50 to 200 µm, are fabricated by femtosecond two photo lithography. Compared to conventional fiber tip tweezers based on chemically wet etched fiber tips, significant trapping efficiency enhancement by a factor of up to 50 is observed in both axial and transverse direction. An outlook on further concepts of enhanced optical fiber tweezers based on 3D diffractive structures will complete the presentation.

Highly efficient counter-propagating fiber-based optical traps are presented which utilize converging beams from fibers with 3D printed diffractive Fresnel lenses on their facet. The use of a converging beam instead of diverging beam in dual-fiber traps creates a strong trapping efficiency in both the axial and the transverse directions. Converging beams with a numerical aperture of up to 0.7 are produced by diffractive Fresnel lenses. These lenses also provide a large focal distance of up to 200 mu m in a moderately high refractive index medium. Fabrication of such diffractive lenses with microsized features at the tip of a fiber is possible by femtosecond two photon lithography. In comparison to chemically etched fiber tips, the normalized trap stiffness of dual-fiber tweezers is increased by a substantial factor of 35-50 when using a converging beam produced by diffractive Fresnel lenses. The large focal length provided by these diffractive structures allows working at a large fiber-to-fiber distance, which leads to larger space and the freedom to combine other spectroscopy and analytical methods in combination with trapping.

The LiMgBO3 nanoparticles prepared by using Pechini process. The crystallinity, structure and morphology of the prepared LiMgBO3 nanoparticles were investigated by X-ray diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) respectively-ray diffraction (XRD) studies of the prepared samples confirmed the formation of crystalline pure monoclinic LiMgBO3 structure. The Fourier transform infrared (FTIR) spectroscopy studies of the prepared samples confirmed the formation of the LiMgBO3 structured nanoparticles. Scanning electron microscopy (SEM) micrographs confirmed the spherical nanoparticles morphologies of LiMgBO3 sample. The electrical conductivities studies of LiMgBO3 nanoparticles were studied through impedance spectroscopy measurements.

Need for a stable polymeric material with an excellent biocompatibility property is the most sought one in the field of implant science and engineering. The material’s scale up requires a complex mechanism or environment or the precursors to develop the material itself require an investment, i.e. the overall process cum procedure might not be economical. Here, in this paper, an attempt has been made to synthesize, a polymer based nanocomposite comprising titanium di oxide nanoparticles and hydroxyapatite nanoparticles as fillers; distributed within a polyurethane matrix which is economical and could be scaled up easily. The same has been characterized to understand their structure, morphology, mechanical property and in vitro biocompatibility through XRD, SEM, tensile tests and simulated body fluid tests. From the characterizations it was found that, the material was stable, biocompatible under tough conditions and the material had a simple foam structure (porous) except for which the boundaries that are shared by the pores are rigid providing the material with a good mechanical strength.

Integrated water resources management (IWRM) is a universally accepted, rational concept for development and management of the water resources of any region or river basin. A long way, however, is to be covered between the concept and practice of IWRM, primarily on account of nonavailability of a methodology to apply IWRM in a real-world situation. Moreover, due to political factors, the application of the concept of IWRM is further constrained in the case of transnational basins. In this study, an area of 11,000 sq km constituting the lower portions of the basins of two contiguous rivers Bagmati and Kamla in North Bihar in the eastern part of India has been chosen as a case study. The upper parts of these basins lie to the north in the neighboring country of Nepal in the sub Himalayan zones. A methodology for suboptimum development and management of water resources of the study region has been evolved by integrating its dominant water resources problems of recurrent floods, fragile drainage, frequent agricultural drought,and high agro potentiality. The methodology is based on considering floods as independent events, drainage as dependent on floods, and topography and irrigation as an activity subject to human control and intervention. For this purpose, the study region has been divided into flood zones on the basis of its inundation characteristics with the help of satellite imageries and image analysis. Irrigation developed on this basis has been shown to ensure an increase in annual agricultural production from 1.14 million MT to 11.8 million MT, a 10-time increase.

Caractérisation spectroscopique de nanoparticules piégées optiquement Depuis quelques décennies, les pinces optiques sont devenues un outil de piégeage et de manipulation sans contact de nanoparticules. Le piégeage optique à l'aide de fibres optiques est une approche complémentaire et polyvalente qui permet l’intégration aisée d'autres techniques expérimentales telles que la spectroscopie. Dans ce contexte, nous avons étudié le piégeage optique de nanoparticules à l'aide de deux configurations de pinces distinctes dans l'air et l'eau, respectivement. Le piégeage des particules dans l'air a été observé comme difficile, en utilisant un faisceau divergent produit par des fibres nanostructurées, car il ne pouvait pas attirer les particules vers le centre du faisceau lumineux. En revanche, le piégeage des particules dans l'eau s'est avéré très efficace, ce qui a été réalisé en utilisant deux pointes de fibres coniques opposées. Pour améliorer encore l'efficacité et la flexibilité de piégeage de cette configuration, nous avons implémenté deux fibres imprimées en 3D différentes: une lentille de Fresnel et des fibres à réflexion interne totale (TIR). Cette configuration expérimentale a été utilisée pour le piégeage optique et la caractérisation spectroscopique de nanobâtonnets dopés à l'europium en employant deux types de fibres différents. Dans un premier temps, nous avons étudié le piégeage stable de nanobâtonnets en contact vaec la pointe à l'aide d'un faisceau divergent. Deuxièmement, le piégeage efficace de nanobâtonnets a été réalisé en utilisant les faisceaux convergents à contre-propagation de deux fibres à lentille de Fresnel à une distance d'environ 200 µm entre ces fibres. Ces expériences de piégeage de nanorod ont été exploitées pour mesurer la direction et l'émission de photoluminescence Eu3+ résolue en polarisation. L’émission dépendant de la polarisation a été étudiée dans une direction perpendiculaire par rapport à l'axe de la nanobâtonnet, ce qui a permis de déterminer la polarisation σ et π des transitions dipolaires électriques et magnétiques. Nous avons déterminé avec précision l'orientation des nanobâtonnets piégés optiquement à l'aide de vidéos de piégeage et de moyens spectroscopiques. Cela nous motive en outre pour une analyse spectroscopique plus rapide de ces nanobâtonnets du point de vue des expériences microrhéologiques. Dans la dernière expérience, nous avons piégé des nanoparticules d'oxyde plasmonique dans le but d'étudier leur d'absorption optique pour des applications de bio-détection.