Focusing Device Research Articles

Real-time phase error compensation in phase sensitive scanning near-field optical microscopy.

Phase measurements are critical for investigations on the optical properties of surface plasmon polariton (SPP) nanostructures. In this paper, a real-time phase error compensation method based on a phase sensitive scanning near-field optical microscopy (SNOM) measurement system is proposed. The method adopts the common optical path configuration and CMR (common-mode rejection) principle. It can be seen that the phase error compensation is real-time and mainly relies on optical devices, therefore neither post processing nor previous knowledge of environmental effects is required. The causes of the phase drift errors are discussed. We demonstrate experimentally the effectiveness of this method by measuring a SPP focusing device. Regardless of the drift velocity, degree of linearity, or phase accuracy, the compensation method shows great improvement compared to the previous phase sensitive SNOMs. All the measured distributions are in good agreement with theoretical simulations obtained by the finite-different time-domain (FDTD) method.

Preparation of biodegradable polymeric nanoparticles for pharmaceutical applications using glass capillary microfluidics

The aim of this study was to develop a new microfluidic approach for the preparation of nanoparticles with tuneable sizes based on micromixing/direct nanoprecipitation in a coaxial assembly of tapered-end glass capillaries. The organic phase was 1wt% poly(ε-caprolactone) (PCL) or poly(dl-lactic acid) (PLA) in tetrahydrofuran and the antisolvent was Milli-Q water. The size of nanoparticles was precisely controlled over a range of 190–650nm by controlling phase flow rates, orifice size and flow configuration (two-phase co-flow or counter-current flow focusing). Smaller particles were produced in a flow focusing device, because the organic phase stream was significantly narrower than the orifice and remained narrow for a longer distance downstream of the orifice. The mean size of PCL particles produced in a flow focusing device with an orifice size of 200μm, an organic phase flow rate of 1.7mLh−1 and an aqueous-to-organic flow rate ratio of 10 was below 200nm. The size of nanoparticles decreased with decreasing the orifice size and increasing the aqueous-to-organic phase flow rate ratio. Due to higher affinity for water and amorphous structure, PLA nanoparticles were smaller and exhibited a smoother surface and more rounded shape than PCL particles.

Microfluidic device for sheathless particle focusing and separation using a viscoelastic fluid

Continuous sheathless particle separation with high efficiency is essential for various applications such as biochemical analyses and clinical diagnosis. Here, a novel microfluidic device for highly efficient, sheathless particle separation using an elasticity-dominant non-Newtonian fluid is proposed. Our device consists of two stages: sheathless three-dimensional focusing (1 st stage) and separation (2nd stage). It is designed based on the principle of a viscoelasticity-induced particle lateral migration, which promises precise separation of particles in a microfluidic device. Particles of 5- and 10-μm diameters were all focused at the centerline of a circular channel at the 1st stage and successfully separated at the 2nd stage with an efficiency of ∼99.9% using size-based lateral migration of particles induced by the viscoelasticity of the medium. We also demonstrated the capability of our device for separation of blood cells into multiple fractions. The tunability of separable particle size could be achieved by changing the viscoelastic property of the medium and flow rate.

High-Throughput Production of Droplets Using Mini Hydrodynamic Focusing Devices with Recirculation

In this study, a mini hydrodynamic focusing device with two feedback channels was designed to produce droplets of two immiscible liquids with a high throughput. Compared to conventional hydrodynamic focusing devices, the design can prevent the two liquids from forming parallel flows that suppress the dispersed phase from breaking up into droplets with high throughputs. A red aqueous solution and fully hydrogenated kerosene with 0.3 wt % Span 80 surfactant were used as the dispersed phase and continuous phase, respectively. Experiments confirmed that the feedback channels can enhance the interface instability and consequently facilitate the production of droplets. Moreover, an arrangement where the dispersed phase is on both sides of the continuous phase was found to remarkably improve the production of droplets because of the increased interface. The mini hydrodynamic focusing device is suitable for solvent extraction and other chemical processes that require a high surface/volume ratio.

Tunable 4-channel LC focusing device: summarized results and additional functional capabilities

A solution to a general problem for 4-channel liquid crystal (LC) modulator (LC focusing device) of the formation of specified-equipotential-line voltage distribution and on its movement along the aperture is presented. The modulator’s capabilities for the formation and control of light fields in the form of circles, line segments and ellipses of an arbitrary orientation are demonstrated numerically and experimentally.

Nanofocusing of X-ray free-electron lasers by grazing-incidence reflective optics.

Total-reflection mirror devices for X-ray free-electron laser focusing are discussed in terms of optical design, mirror-fabrication technology, a wavefront diagnosis method and radiation-damage testing, as a review of the present status of the focusing optics at the SPring-8 angstrom compact free-electron laser (SACLA). Designed beam sizes of 1 µm and 50 nm, and spot sizes almost matching prediction have been achieved and used to explore topics at the forefront of natural science. The feasibility of these devices is determined to be sufficient for long-term and stable operation at SACLA by investigating the radiation-damage threshold and achievable accuracies in the mirror figure and alignment.

Automation Highlights from the Literature

Automation Highlights from the Literature

LINE OPTICAL TRAPS FORMED BY LC SLM

The methods for generation of optical traps in the form of line segments by means of liquid crystal modulators of two types are addressed in the paper, they are a multi-pixel modulator HOLOEYE HEO 1080P and a tunable liquid crystal focusing device (4-channel modulator) developed by the authors. The numerical and experimental assessment of the capture forces of the generated optical trap is fulfilled. The description of manipulation experiments with microobjects, including biological ones, carried out by the optical traps with the intensity distribution in the form of segments is offered.

Low-voltage paper isotachophoresis device for DNA focusing.

We present a new paper-based isotachophoresis (ITP) device design for focusing DNA samples having lengths ranging from 23 to at least 1517 bp. DNA is concentrated by more than two orders of magnitude within 4 min. The key component of this device is a 2 mm-long, 2 mm-wide circular paper channel formed by concertina folding a paper strip and aligning the circular paper zones on each layer. Due to the short channel length, a high electric field of ~16 kV m(-1) is easily generated in the paper channel using two 9 V batteries. The multilayer architecture also enables convenient reclamation and analysis of the sample after ITP focusing by simply opening the origami paper and cutting out the desired layers. We profiled the electric field in the origami paper channel during ITP experiments using a nonfocusing fluorescent tracer. The result showed that focusing relied on formation and subsequent movement of a sharp electric field boundary between the leading and trailing electrolyte.

Online determination of anisotropy during cellulose nanofibril assembly in a flow focusing device

In order to utilize the high strength and stiffness of cellulose nanofibrils in a macroscopic material or composite, the structure of the elongated fibrils in the material must be controlled.

Staged Inertial Microfluidic Focusing for Complex Fluid Enrichment.

Microfluidic inertial focusing reliably and passively aligns small particles and cells through a combination of competing inertial fluid forces. The equilibrium behavior of inertially focused particles in straight channels has been extensively characterized and has been shown to be a strong function of channel size, geometry and particle size. We demonstrate that channels of varying geometry may be combined to produce a staged device capable of high throughput particle and cell concentration and efficient single pass complex fluid enrichment. Straight and asymmetrically curved microchannels were combined in series to accelerate focusing dynamics and improve concentration efficiency. We have investigated single and multiple pass concentration efficiency and results indicate that these devices are appropriate for routine cell handling operations, including buffer exchange. We demonstrate the utility of these devices by performing a ubiquitous fluorescence staining assay on-chip while sacrificing very little sample or processing time relative to centrifugation. Staged concentration is particularly desirable for point of care settings in which more conventional instrumentation is impractical or cost-prohibitive.

Formation of contour optical traps using a four-channel liquid crystal focusing device

The capabilities and specific features of the formation and dynamic control of so-called contour optical traps using a four-channel liquid crystal modulator are studied theoretically and experimentally. Circular, elliptical and C-shaped traps are formed. Trapping and confinement of absorbing micro-objects by the formed traps are demonstrated.

Hard-X-ray magnetic microscopy and local magnetization analysis using synchrotron radiation.

X-ray measurement offers several useful features that are unavailable from other microscopic means including electron-based techniques. By using X-rays, one can observe the internal parts of a thick sample. This technique basically requires no high vacuum environment such that measurements are feasible for wet specimens as well as under strong electric and magnetic fields and even at a high pressure. X-ray spectroscopy using core excitation provides element-selectivity with significant sensitivities to the chemical states and atomic magnetic moments in the matter. Synchrotron radiation sources produce a small and low-divergent X-ray beam, which can be converged to a spot with the size of a micrometer or less using X-ray focusing optics. The recent development in the focusing optics has been driving X-ray microscopy, which has already gone into the era of X-ray nanoscopy. With the use of the most sophisticated focusing devices, an X-ray beam of 7-nm size has successfully been achieved [1]. X-ray microscopy maintains above-mentioned unique features of X-ray technique, being a perfect complement to electron microscopy.In this paper, we present recent studies on magnetic microscopy and local magnetic analysis using hard X-rays. The relevant instrumentation developments are also described. The X-ray nanospectroscopy station of BL39XU at SPring-8 is equipped with a focusing optics consisting of two elliptic mirrors, and a focused X-ray beam with the size of 100 × 100 nm(2) is available [2]. Researchers can perform X-ray absorption spectroscopy: nano-XAFS (X-ray absorption fine structure) using the X-ray beam as small as 100 nm. The available X-ray energy is from 5 to 16 keV, which allows nano-XAFS study at the K edges of 3d transition metals, L edges of rare-earth elements and 5d noble metals. Another useful capability of the nanoprobe is X-ray polarization tunability, enabling magnetic circular dichroism (XMCD) spectroscopy with a sub-micrometer resolution. Scanning XMCD imaging, XMCD measurement in local areas, and element-specific magnetometry for magnetic particles/magnetic devices as small as 100 nm can be performed. Nano-XAFS application includes visualization of the chemical state in a particle catalyst [3] and phase-change memory devices [4]. For magnetic microscopic study, magnetization reversal processes of an individual magnetic CoPt dot in bit-patterned media have directly been observed [2]. Imaging of the chemical distribution and magnetic domain evolution in a Nd-Fe-B sintered magnet in demagnetization processes is presented.

New progress on the Fresnel imager for UV space astronomy

We propose a next generation space instrument: the Fresnel imager, a large aperture and lightweight focusing device for UV astrophysics.

Formation of steady compound cone-jet modes and multilayered droplets in a tri-axial capillary flow focusing device

A novel method for forming steady cone-jet modes and multilayered droplets is developed based on capillary flow focusing geometry using tri-axial needles. The needles manufactured by a laser beam welding process can be readily cleaned, assembled and aligned. A tri-axial capillary flow focusing (TCFF) device is assembled in order to focus a combination of different liquids in the core of a high-speed gas stream co-flowing through a small orifice. The effects of main control process parameters on the characteristics of compound cone-jet mode are studied. Under appropriate working conditions, steady cone-jet configurations with three layers of liquids are obtained, resulting in multilayered droplets with outer shell, middle layer and inner core. The process can also produce monodisperse droplets at smaller scales by releasing the outer shell and the middle liquid. The new design of tri-axial needles and TCFF devices enables reliable encapsulation of multiple components in one shell for potential applications in multimodal imaging, drug delivery, material processing and biomedicine.

Development and demonstration of a multi-channel spheroidal focusing device for neutron beams

A multi-channel neutron focusing mirror is a compact device that can effectively enhance neutron intensity because the multi-channel structure can cover a large divergence of a neutron beam. In this study, we attempted to develop a compact multi-channel spheroidal (MS) neutron focusing device for two-dimensional focusing. A prototype of the MS mirror consists of three spheroidal mirrors of different diameters. The mirrors are fabricated through the copper plating method without supermirror coating and are aligned coaxially using ring-shaped spacers. The MS mirror was demonstrated at beam line 10 NOBORU port at J-PARC, which provides neutron beams with time-of-flight spectra. A gain factor of 6 in neutron intensity was obtained over wavelengths greater than 0.5 nm, and an imaging test with sample scanning could be performed with an exposure time of 10 s. A Gd-patterned standard sample was employed and a 2D image with a spatial resolution of 200 μm was successfully obtained.

Plasmonic Micro Lens for Extraordinary Transmission of Broadband Light

Extraordinary transmittance and focusing of light in quasi far field region using miniaturized optical devices is a daunting task. A polarization independent, broadband, planar metallic transmissive micro aperture capable of achromatically focusing visible light in quasi far field region is proposed. The calculated enhancement factor of transmission efficiency was about ~2.2. The total transmission after the aperture is about 60%. This high throughput focusing device will open new avenues for focusing electromagnetic energy in the wide area of sensors and energy concentration.

Focusing of intense and divergent ion beams in a magnetic mass analyzer.

A magnetic mass analyzer is used to determine the beam composition of a vacuum arc ion source. In the analyzer, we used the concentric multi-ring electrodes to focus the intense and divergent ion beams. We describe the principle, design, and the test results of the focusing device. The diameter of the beam profile is less than 20 mm when the accelerating voltage is 30 kV and the focusing voltage is about 2.0 kV. The focusing device has been successfully used in the magnetic mass analyzer to separate Ti(+), Ti(2+), and Ti(3+).

Dynamic Strategies and Management of Focusing Devices

This paper examines how dynamic strategies and underlying focusing devices lead to dynamic competitive advantage. Our methodology is an analysis based on the simple mode of focusing device and innovation. We show that quality-improving and cost-reducing strategies are facilitated under a productivity-based pricingscheme, while a hybrid strategy is favoured by having a marginal productivity-based pricing scheme as the underlying focusing device of innovation. We also argue that a hybrid strategy achieves dynamic efficiency, so that cost-reducing and quality-improving strategies should converge towards ahybrid strategy over time, to attain dynamic competitive advantage. The implications of these results are threefold. First, the firm should determine the appropriate direction of innovationtrajectories, rather than a competitive position. Second, the firm should identify its current focusing device and examine whether it is congruent with the desired dynamic strategy. Third, over the long term, the firm should adopt a hybrid strategy. The value of this paper is significant as it provides the formal model of dynamic strategies.

Solitary waves in a chain of repelling magnets

We study experimentally, numerically, and theoretically the dynamics of a one dimensional array of repelling magnets. We demonstrate that such systems support solitary waves with a profile and propagation speed that depend on the amplitude. The system belongs to the kind of nonlinear lattices studied in [Friesecke and Matthies, Physica D 171, 211–220 (2002)] and exhibits a sech2 profile in the low energy regime and atomic scale localization in the high energy regime. Such systems may find potential applications in the design of novel devices for shock absorption, energy localization and focusing. Furthermore, due to the similarity of the magnetic potential with the potentials governing atomic forces, the system could be used for a better understanding of important problems in physics and chemistry.