Focusing Device Research Articles

Numerical simulation of droplet formation in a Co-flow microchannel capillary device

In this article, a numerical simulation of the droplet formation in a Co-flow microchannel capillary device, and the influencing factors of the formation of droplets are studied. The level set method is used to track the two-phase interface and droplet formation. In the Co-flow focusing device, we explored the influencing factors of the size of the generated droplets. In the Co-flow focusing device, we explored the influences of various factors on the droplet size, generation frequency, and the droplet pressure at the centerline. The results demonstrate that an increased ratio of dispersed phase velocity to continuous phase velocity leads to a significant increase in the volume of generated droplets, a significant decrease in droplet generation frequency, and a significant decrease in droplet pressure at the centerline. Furthermore, as the viscosity of continuous phase increases, the volume of generated droplets decreases significantly, the frequency of droplet generation increases significantly, and the pressure of droplets at the centerline decreases significantly. Additionally, an elevated contact angle between the continuous phase and the wall results in a slight increase in the volume of generated droplets, alongside a reduction in droplet generation frequency and a decrease in droplet pressure at the centerline. Moreover, with the increase in interfacial tension, there is a significant increase in the volume of droplet generation, a significant decrease in the frequency of droplet generation, and a significant increase in the pressure of droplets at the centerline.

Development of a large stroke 3-DOF piezoelectric steering mirror for optical system

The steering mirrors and the focusing mechanisms are the key components of the optical system. Traditional steering mirrors driven by voice coil actuator or piezoelectric stack actuator have the disadvantages of short stroke, self-locking difficulty and poor structural reliability. These defects limit the performance of the steering mirrors and make it difficult to be compatible with the focusing mechanism. As a result, additional focusing devices are required in the optical system, which significantly increases the complexity of the system. To simplify the optical system, a large stroke three-degree-of-freedom (3-DOF) piezoelectric steering mirror (PSM) which can realize both light path adjustment and focus adjustment is proposed in this study. Two rotational degrees of freedom of the PSM are used to adjust the light path, and a translational degree of freedom is used to adjust the focus. The screwed-typed piezoelectric actuators (STPAs) are designed to drive the PSM by exciting the travelling wave. The feasibility of the operating principle and reliability of the proposed PSM have been verified by finite element simulation. A prototype of the PSM is fabricated and tested. The experimental results show that the PSM achieves rotational degrees of freedom around the x-axis, y-axis and translational degree of freedom along the z-axis with maximum ranges of ±0.17 rad, ±0.17 rad, and ±10 mm, respectively, meeting the application requirements of the optical systems. The resolutions of the two rotary motions of the PSM are 28 μrad, and 21 μrad, respectively, and that of the translational motion is 0.5 μm. Finally, the position adjustment and focusing operations of the image are demonstrated to validate the potential application of PSM in optical systems.

Functionalized monodisperse microbubble production: microfluidic method for fast, controlled, and automated removal of excess coating material

Functionalized monodisperse microbubbles have the potential to boost the sensitivity and efficacy of molecular ultrasound imaging and targeted drug delivery using bubbles and ultrasound. Monodisperse bubbles can be produced in a microfluidic flow focusing device. However, their functionalization and sequential use require removal of the excess lipids from the bubble suspension to minimize the use of expensive ligands and to avoid competitive binding and blocking of the receptor molecules. To date, excess lipid removal is performed by centrifugation, which is labor intensive and challenging to automate. More importantly, as we show, the increased hydrostatic pressure during centrifugation can reduce bubble monodispersity. Here, we introduce a novel automated microfluidic ’washing’ method. First, bubbles are injected in a microfluidic chamber 1 mm in height where they are left to float against the top wall. Second, lipid-free medium is pumped through the chamber to remove excess lipids while the bubbles remain located at the top wall. Third, the washed bubbles are resuspended and removed from the device into a collection vial. We demonstrate that the present method can (i) reduce the excess lipid concentration by 4 orders of magnitude, (ii) be fully automated, and (iii) be performed in minutes while the size distribution, functionality, and acoustic response of the bubbles remain unaffected. Thus, the presented method is a gateway to the fully automated production of functionalized monodisperse microbubbles.

Optical design and analysis of a high-speed triple galvanometer laser 3D scanning system

In this paper, a triple galvanometer laser three-dimensions (3D) scanning system (TGLSS) was proposed. The system consisted of three galvanometers and two parabolic mirrors, with rapid movement of the laser focus in 3D space by rotations of the three galvanometers. The optical principle of the TGLSS was analyzed, and the method of designing TGLSS by geometrical optics and Abbe’s sine condition was given in detail. Scanning range and focusing quality were analyzed by optical simulations. An experiment was carried out to verify the feasibility of TGLSS. The implications of TGLSS for reflective dynamic focusing device (RDFD)-based laser system and their impact on technologically relevant applications were discussed. The great potential for enhancing the speed of advanced laser processing in 3D space was offered by TGLSS.

Multiresponsive Liquid Crystal Collagen Guides Mussel Byssus Formation.

Marine mussels fabricate tough collagenous fibers known as byssal threads to anchor themselves. Threads are produced individually in minutes via secretion of liquid crystalline (LC) collagenous precursors (preCols); yet the physical and chemical parameters influencing thread formation remain unclear. Here, we characterized the structural anisotropy of native and artificially induced threads using quantitative polarized light microscopy and transmission electron microscopy to elucidate spontaneous vs regulated aspects of thread assembly, discovering that preCol LC phases form aligned domains of several hundred microns, but not the cm-level alignment of native threads. We then explored the hypothesized roles of mechanical shear, pH, and metal ions on thread formation through in vitro assembly studies employing a microfluidic flow focusing device using purified preCol secretory vesicles. Our results provide clear evidence for the role of all three parameters in modulating the structure and properties of the final product with relevance for fabrication of collagenous scaffolds for tissue engineering applications.

Three-dimensional surface analysis of iron-based materials using synchrotron Mössbauer source

A novel three-dimensional surface analysis system for iron-based solid materials has been developed. This system is composed of a synchrotron Mössbauer source, an X-ray focusing device, a precision stage, a gas flow proportional counter for conversion electron measurements, and multiple multichannel scalers. The performance was evidenced by determining the spatial distribution of the iron oxide abundance on a laser-ablated iron foil surface. This system can be widely utilized as a powerful analytical tool in steel science for corrosion, welding, and laser surface modification.

Are monodisperse phospholipid-coated microbubbles “mono-acoustic?”

Phospholipid-coated microbubbles with a uniform acoustic response are a promising avenue for functional ultrasound sensing. A uniform acoustic response requires both a monodisperse size distribution and uniform viscoelastic shell properties. Monodisperse microbubbles can be produced in a microfluidic flow focusing device. Here, we investigate whether such monodisperse microbubbles have uniform viscoelastic shell properties and thereby a uniform “mono-acoustic” response. To this end, we visualized phase separation of the DSPC and DPPE-PEG5000 lipid shell components and measured the resonance curves of nearly 2000 single and freely floating microbubbles using a high-frequency acoustic scattering technique. The results demonstrate inhomogeneous phase-separated shell microdomains across the monodisperse bubble population, which may explain the measured inhomogeneous viscoelastic shell properties. The shell viscosity varied over an order of magnitude and the resonance frequency by a factor of two indicating both a variation in shell elasticity and in initial surface tension despite the relatively narrow size distribution.

Large focal length planar focusing of Dyakonov polaritons in hyperbolic metamaterial

Achieving subwavelength optical focusing is of great importance in nanophotonics. However, achieving focusing with both a small focal spot size and a large focal length remains elusive so far. Here, a large focal length planar focusing device is presented, utilizing highly oriented Dyakonov polaritons in hyperbolic metamaterial with periodic silver rings as the excitation source. Experimental results show that by controlling the size of the excitation sources, the focal length can reach 6λ0 (where λ0 is the illumination wavelength), and the focal spot size can be reduced to λ0/10. This method provides new prospects for planar polariton optical applications.

Elasto-inertial particle focusing in sinusoidal microfluidic channels.

Dean flow existing in sinusoidal channels could enhance the throughput and efficiency for elasto-inertial particle focusing. However, the fundamental mechanisms of elasto-inertial focusing in sinusoidal channels are still unclear. This work employs four microfluidic devices with symmetric and asymmetric sinusoidal channels to explore the elasto-inertial focusing mechanisms over a wide range of flow rates. The effects of rheological property, flow rate, sinusoidal channel curvature, particle size, and asymmetric geometry on particle focusing performance are investigated. It is intriguing to find that the Dean flow makes a substantial contribution to the particle elasto-inertial focusing. The results illustrate that a better particle focusing performance and a faster focusing process are obtained in the sinusoidal channel with a small curvature radius due to stronger Dean flow. In addition, the particle focusing performance is also related to particle diameter and rheological properties, the larger particles show a better focusing performance than smaller particles, and the smaller flow rate is required for particles to achieve stable focusing at the outlet in the higher concentration of polyvinylpyrrolidone solutions. Our work offers an increased knowledge of the mechanisms of elasto-inertial focusing in sinusoidal channels. Ultimately, these results provide supportive guidelines into the design and development of sinusoidal elasto-inertial microfluidic devices for high-performance focusing.

Tunable Device for Long Focusing in the Sub-THz Frequency Range Based on Fresnel Mirrors.

THz radiation has gained great importance due to its potential applications in a wide variety of fields. For this reason, continuous efforts have been made to develop technological tools for use in this versatile band of the electromagnetic spectrum. Here, we propose a reflecting device with long focusing performances in the sub-THz band, using a bimirror device in which the relative angle is mechanically adjusted with the displacement of one of the mirrors. Despite the simplicity of the setup, the performance of this device is satisfactory down to a frequency of 0.1 THz. Theory and experience confirm that the bimirror is capable of focusing 0.1 THz radiation with a 2× magnification of the maximum input intensity while maintaining a longitudinal full width at half maximum (FWHM) of about 6 mm, which is about 12 times the depth of focus of a cylindrical optical element of the same focal length. In the absence of suitable THz equipment, the invariance property of the Fresnel diffraction integral allowed the predicted behavior to be tested in the THz range using conventional equipment operating at visible frequencies.

Combined helical-blade-strengthened co-flow focusing and high-throughput screening for the synthesis of highly homogeneous nanoliposomes

Nanoliposomes have been widely employed as promising drug delivery vehicles for the treatment of various diseases. However, the large-scale synthesis of drug-loaded nanoliposomes manifesting a highly uniform particle size is impeded by several unmet challenges. Herein a novel helical-blade-strengthened co-flow focusing (HBSCF) device was developed by installing multiple parallel helical blades in a commonly used co-flow focusing microfluidic device. This transformation in the microchannel structure may accelerate the mixing of aqueous and lipid streams in a radial direction, thereby affording the production of nanoliposomes with a significantly lower polydispersity index (PDI) value in terms of particle size. Moreover, a high-throughput experimental platform was developed by employing HBSCF device alongside its integration with various automation modules, which afforded 672 distinct experimental schemes for the synthesis and size characterization of drug-loaded nanoliposomes within 40 h. Afterwards, based on the above obtained large data set of nanoliposomes, a typical machine learning (ML) model pertaining to particle size was established to predict candidate synthesis schemes for the desired average particle size. Therefore, by narrowing the screening ranges through ML, the final synthesis scheme capable of producing liposomes with the desired particle size along with minimum PDI value can be precisely and rapidly obtained using automated experiments based on the same platform. Taken together, an effective integration of the HBSCF synthesis along with an automated high-throughput experimental platform may have broad implications for the industrialization and clinical application of nanomedicine.

A step towards the diagnostic of the ITER first wall: in-situ LIBS measurements in the WEST tokamak

Abstract As part of the development of proven diagnostics allowing the characterization of ITER’s PFUs (Plasma Facing Units) without dismantling, LIBS (Laser-Induced Breakdown Spectroscopy) is a serious candidate for determining the multi-elemental composition. In this article, we report a measurement campaign carried out within the WEST tokamak using an original device based on the following technological choices. (1) The laser source and the spectrometer are placed outside the tokamak. (2) The laser pulses are conveyed by an optical fiber. (3) The signals are collected by a second optical fiber. (4) The optical focusing and collection device is placed in the desired location by a remote handling arm (AIA, Articulated Inspection Arm). The processed signals allow the measurement of the composition of the irradiated material. The technological choices are discussed in the light of their implementation and proposals are made for a more efficient future version of the system.

Continuous light-guide control of melts temperature in induction furnaces

The article is devoted to the question of the most effective for the full use of the induction furnaces technological flexibility continuous temperature control. The aim of the work is to create a light-guide technology for continuous temperature control of the processes of induction melting, treatment and pouring of liquid metal in metallurgy of machine building. The investigations of crucible and channel, melting, holding and pouring induction furnaces from the standpoint of light-guide thermometry have been developed. Materials, designs, as well as technologies of manufacturing, mounting and safe operation of the light-guide and auxiliary devices have also been investigated. Using the results of complex studies, the base light-guide thermometry system, general and particular methods of the light-guide temperature measurements have been developed. On the base of the Huygens construction, as well as the laws of geometric and crystal optics, techniques for calculation of the optical characteristics of the light-guide and focusing devices, as well as schemes of their optical joint have been developed. These techniques increase the metrological characteristics of the light-guide thermometry. Standard construction of the secondary part of thermometry system requires classical pyrometry methods application. These methods are acceptable for continuously operated metallurgical aggregates, where stable emissivity of the light-guide operating end takes place. The secondary part of thermometry system has been modernized in order to widen application field of light-guide thermometry on periodically operated metallurgical aggregates where emissivity of light-guide immersion end randomly changes. Modernized secondary part is purposed for spectral (multicolor) pyrometry methods realization. These methods minimize influence of the instability of emissivity of light-guide immersion end on methodical errors of temperature measurements. Research and industrial exploitation, at domestic and foreign enterprises, have shown obvious metrological advantages of the light-guide thermometry technology in comparison with known solutions. Implementation of the light-guide thermometry systems on induction furnaces has high technical-economic efficiency, including by reduction the spoilage of metal products and resource costs for production. Keywords: induction furnace, continuous temperature control, light-guide thermometry, amorphous, poly- and single-crystalline materials, measurement error, Huygens construction, technical-economic efficiency.

An efficient and accurate semi-analytical matching technique for waveguide-fed antennas

Several RF and microwave radiating devices, such as horn antennas, Fabry–Perot cavity antennas, and aperture-fed focusing devices, are excited through rectangular waveguides. The impedance matching of the overall system (from the waveguide feed to the radiating aperture) is a task of crucial importance that is often addressed by means of brute-force parameter-sweep full-wave analyses or blind optimization algorithms. In both cases, a significant amount of memory and time resources are required. For this purpose, we propose here a simple, yet effective solution, which only requires a single full-wave simulation and a semi-analytical procedure. The former is used to retrieve the antenna input impedance at the end of the waveguide port excitation. The semi-analytical procedure consists in a transmission-line equivalent circuit that models two waveguide discontinuities (namely two capacitive irises) within the waveguide section, whose position and geometric features are finely tuned to obtain a satisfactory impedance matching around the working frequency. The proposed method is shown to be effective in diverse and attractive application-oriented contexts, from the impedance matching of a Fabry–Perot cavity antenna to that of a wireless near-field link between two aperture-fed focusing devices. A remarkable agreement between full-wave simulations and numerical results is found in all cases. Thanks to its versatility, simplicity, and a rather low demand of computational resources, the proposed approach may become an essential tool for the effective design of waveguide-fed antennas.

Ultracompact mirror device for forming 20-nm achromatic soft-X-ray focus toward multimodal and multicolor nanoanalyses

Nanoscale soft-X-ray microscopy is a powerful analysis tool in biological, chemical, and physical sciences. To enhance its probe sensitivity and leverage multimodal soft-X-ray microscopy, precise achromatic focusing devices, which are challenging to fabricate, are essential. Here, we develop an ultracompact Kirkpatrick-Baez (ucKB) mirror, which is ideal for the high-performance nanofocusing of broadband-energy X-rays. We apply our advanced fabrication techniques and short-focal-length strategy to realize diffraction-limited focusing over the entire soft-X-ray range. We achieve a focus size of 20.4 nm at 2 keV, which represents a significant improvement in achromatic soft-X-ray focusing. The ucKB mirror extends soft-X-ray fluorescence microscopy by producing a bicolor nanoprobe with a 1- or 2-keV photon energy. We propose a subcellular chemical mapping method that allows a comprehensive analysis of specimen morphology and the distribution of light elements and metal elements. ucKB mirrors will improve soft-X-ray nanoanalyses by facilitating photon-hungry, multimodal, and polychromatic methods, even with table-top X-ray sources.

Tunable and super-wide angle defocusing lens large phase modulator

Traditional terahertz wavefront modulators exhibit significant limitations in controlling optical wavefronts. In order to address the adjustability issues of terahertz wavefront modulators, we have developed a novel optical device based on the tunability of Fermi energy levels. Structurally, we find the ability to modulate the Fermi energy levels of graphene by modulating the carrier concentration. We can also change the phase of the light, causing the transmission path of the light as it passes through the graphene array to change, affecting the position of the backfocusing focal point, thus realizing a dynamically adjustable backfocusing effect. Theoretically, employing Dirac notation and Matrix analyze, reveals the corresponding relationship between Fermi level and phase shift. Specifically, one group Fermi levels induces a set of modulated phase changes. Experimental results demonstrate that the proposed modulator offers a large phase modulation range, enabling 2π phase adjustments. Moreover, it accurately focuses on a predefined focal point located at 400 um, with a numerical aperture of 0.882, a resolution of 30.39, and a full-width at half-maximum of 38. The substantial numerical aperture and small full-width at half-maximum imply that the lens can focus more light while maintaining high resolution, enhanced optical efficiency, and concentrated light focusing. At the same time, by adjusting the position of the Fermi energy level, we have succeeded in realizing a wide-angle focusing effect up to 90°. This capability extends the terahertz wave’s focusing within a wide range, expanding the application scope of traditional focusing devices.

Sheathless inertial particle focusing methods within microfluidic devices: a review.

The ability to manipulate and focus particles within microscale fluidic environments is crucial to advancing biological, chemical, and medical research. Precise and high-throughput particle focusing is an essential prerequisite for various applications, including cell counting, biomolecular detection, sample sorting, and enhancement of biosensor functionalities. Active and sheath-assisted focusing techniques offer accuracy but necessitate the introduction of external energy fields or additional sheath flows. In contrast, passive focusing methods exploit the inherent fluid dynamics in achieving high-throughput focusing without external actuation. This review analyzes the latest developments in strategies of sheathless inertial focusing, emphasizing inertial and elasto-inertial microfluidic focusing techniques from the channel structure classifications. These methodologies will serve as pivotal benchmarks for the broader application of microfluidic focusing technologies in biological sample manipulation. Then, prospects for future development are also predicted. This paper will assist in the understanding of the design of microfluidic particle focusing devices.

Application of single-molecule analysis to singularity phenomenon of cells.

Single-molecule imaging in living cells is an effective tool for elucidating the mechanisms of cellular phenomena at the molecular level. However, the analysis was not designed for throughput and requires high expertise, preventing it from reaching large scale, which is necessary when searching for rare cells that induce singularity phenomena. To overcome this limitation, we have automated the imaging procedures by combining our own focusing device, artificial intelligence, and robotics. The apparatus, called automated in-cell single-molecule imaging system (AiSIS), achieves a throughput that is a hundred-fold higher than conventional manual imaging operations, enabling the analysis of molecular events by individual cells across a large population. Here, using AiSIS, we demonstrate the single-molecule imaging of molecular behaviors and reactions related to tau protein aggregation, which is considered a singularity phenomenon in neurological disorders. Changes in the dynamics and kinetics of molecular events were observed inside and on the basal membrane of cells after the induction of aggregation. Additionally, to detect rare cells based on the molecular behavior, we developed a method to identify the state of individual cells defined by the quantitative distribution of molecular mobility and clustering. Using this method, cellular variations in receptor behavior were shown to decrease following ligand stimulation. This cell state analysis based on large-scale single-molecule imaging by AiSIS will advance the study of molecular mechanisms causing singularity phenomena.

Study on binary-amplitude far-field super-resolution achromatic focusing devices

The far-field super-resolution focusing devices possess characteristics such as super-resolution focusing, achromatic, small size and easy machining, which make them highly promising in optical imaging, optical microscopy and lithography. In this work, we propose a binary-amplitude modulation-based method for generating far-field super-resolution achromatic focusing. By using the principles of optical super-oscillation, combined with angular spectral diffraction theory and binary particle swarm optimization (BPSO), we optimize the binary amplitude-type far-field super-resolution focusing devices, which have an identical radius of 100<i>λ</i> but different focal lengths: <i>λ</i><sub>1</sub> = 405 nm, <i>λ</i><sub>2</sub> = 532 nm and <i>λ</i><sub>3</sub> = 632.8 nm, respectively. Additionally, an achromatic metalens is integrated by using Boolean AND operation. To assess the feasibility of our proposed approach, numerical simulations are conducted via COMSOL Multiphysics employing FEM analysis. The simulation results demonstrate that the generated spots are located at 25.105<i>λ</i>, 25.106<i>λ</i>, and 25.105<i>λ</i>, respectively. The corresponding full width at half maximum (FWHM) values are 0.441<i>λ</i><sub>1</sub> (0.179 μm), 0.469<i>λ</i><sub>2</sub> (0.249 μm) and 0.427<i>λ</i><sub>3</sub> (0.270 μm), which are smaller than the Abbe diffraction limit, and the far-field super-resolution achromatic focusing is realized. The sidelobe ratios are at low levels, i.e. 12.5%, 12.6%, and 14.2%. The binary amplitude-type far-field super-resolution achromatic devices have the advantages of easy machining, achromatism and super-resolution, and are suitable for miniaturization and integration of optical systems.

A reconfigurable acoustic coding metasurface for tunable and broadband sound focusing

The targeted concentration of acoustic waves has significant implications for industrial nondestructive testing, ultrasound diagnosis, and medical treatment. Most conventional sound-focusing metasurfaces suffer from an untunable focus, narrow bandwidth, and fixed geometric configurations, which severely constrain their practical utility. In this paper, we propose a reconfigurable acoustic coding metasurface composed of two coding units with high transmittance and transmitted phases of 0 and π for realizing tunable and broadband sound focusing. Through the straightforward manipulation of each unit structure and alterations in the coding sequences, precise control of the focus position across the entire working plane is attainable, enabling both tunable axial-axis and off-axis sound-focusing effects. Moreover, the sound-focusing performance of the proposed metasurface is excellent within a broad frequency range from 3000 to 5500 Hz. The experimental results are consistent with theoretical expectations and numerical simulations. This work lays a practical foundation for the design of acoustic devices for tunable and broadband sound focusing.