Separation Of Micro Research Articles

A technique for depositing iron, tungsten, molybdenum, and chrome in the determination of selenium and tellurium in alloy steel by ICP-AES method

Direct determination of the content of selenium and tellurium impurities in metallurgical materials by the method of inductively coupled plasma atomic emission spectroscopy (ICP-AES) is difficult due to spectral and non-spectral interference from macrocomponents present in the materials under study. The separation of micro-(Se, Te) and macro-components (Fe, W, Mo, Cr, Cu, Ni, Co) through preliminary precipitation is the goal of the study. The use of barium acetate and sodium fluoride as precipitants are shown to provide an effective separation of Se and Te from Fe, W, Mo, and Cr (the content in the analyzed solution is less than 0.1 wt.% of the original) and partial separation from Cu, Ni, and Co (the content in the analyzed solution from 25 to 55 wt.% of the original). Optimal conditions for the deposition of macrocomponents (Fe, W, Mo, Cr) and inhibition of the process of coprecipitation of selenium and tellurium on sediments of macrocomponents for their subsequent ICP-AES determination were determined. The optimal pH for the precipitation of macrocomponents equals 1. The optimal mass of precipitants (barium acetate and sodium fluoride) is 10 and 3 g, respectively. To inhibit the process of coprecipitation of selenium and tellurium on sediments of macrocomponents, it is proposed to use hydrofluoric acid. The optimal volume of hydrofluoric and hydrochloric acids for inhibiting the process of coprecipitation of analytes on sediments of macrocomponents was determined (3 and 6 cm3, respectively). The developed procedure for separating micro-Se, Te from macro-components was tested on standard samples of alloyed steels using the «spike» method. The technique is characterized by satisfactory accuracy and reproducibility, the limit of determination of analytes after separation of macrocomponents is 10–3 wt.%.

Optical sorting by trajectory tracking with high sensitivity near the exceptional points

Exceptional points (EPs) in non-Hermitian systems embody abundant new physics and trigger various novel applications. In the optical force system, the motion of a particle near its equilibrium position is determined by the optical force stiffness matrix (OFSM), which is inherently non-Hermitian when the particle is illuminated by vortex beams. In this study, by exploiting the rapid variations in eigenvalues and the characteristics of particle motion near EPs of the OFSM, we propose a method to sort particles with subtle differences in their radii or refractive indices based on their trajectories in air. We demonstrate that the trajectory of a particle with parameters slightly larger than those corresponding to certain EPs closely resembles an ellipse. The increase in the major axis of the ellipse can be several orders of magnitude larger than the increase in particle radius. Furthermore, even a slight change in the refractive index can not only significantly alter the size of the ellipse but also rotate its orientation angle. Hence, particles with subtle differences can be distinguished by observing the significant disparities in their trajectories. This approach holds promise as a technique for the precise separation of micro and nanoscale particles.

Improving flotation separation of micro Si/SiC particles from silicon sawing waste by surface hydrophilic modification

Silicon sawing waste (MSW) produced by mortar cutting causes serious environmental issues and a waste of high-purity silicon. The major obstacle in the recovery of high-purity silicon (Si) is the separation of microscale Si and silicon carbide (SiC) in MSW. In this study, micro Si/SiC in silicon sawing waste was separated effectively by bulk-oil flotation after surface hydrophilic modification of Si particles. The structural evolution of micro Si surface after wet oxidization in water and acid was characterized by FT-IR, TEM, and XPS. Specifically, the wet oxidization process reduced the contact angle from 63 ± 0.3° to 18.5° of Si surface for the coating of an amorphous oxide with hydroxy groups on Si particles enhanced the wettability. The amorphous oxide layer with hydroxy coated on Si particles played a key role in enhancing the wettability of Si particles. The wet oxidization is essential to the subsequent flotation separation for the contact angle of SiC keeping at around 60.3°. The wettability of silicon sawing waste was further examined by the absorption of diesel. The effects of pH value and solid concentration on separation efficiency were studied. The best result obtained was 95% in Si recovery and 97.1 wt% in Si purity.

Progress of Microfluidic Continuous Separation Techniques for Micro-/Nanoscale Bioparticles.

Separation of micro- and nano-sized biological particles, such as cells, proteins, and nucleotides, is at the heart of most biochemical sensing/analysis, including in vitro biosensing, diagnostics, drug development, proteomics, and genomics. However, most of the conventional particle separation techniques are based on membrane filtration techniques, whose efficiency is limited by membrane characteristics, such as pore size, porosity, surface charge density, or biocompatibility, which results in a reduction in the separation efficiency of bioparticles of various sizes and types. In addition, since other conventional separation methods, such as centrifugation, chromatography, and precipitation, are difficult to perform in a continuous manner, requiring multiple preparation steps with a relatively large minimum sample volume is necessary for stable bioprocessing. Recently, microfluidic engineering enables more efficient separation in a continuous flow with rapid processing of small volumes of rare biological samples, such as DNA, proteins, viruses, exosomes, and even cells. In this paper, we present a comprehensive review of the recent advances in microfluidic separation of micro-/nano-sized bioparticles by summarizing the physical principles behind the separation system and practical examples of biomedical applications.

Particle separation in microfluidics using different modal ultrasonic standing waves

Microfluidic technology has great advantages in the precise manipulation of micro and nano particles, and the separation of micro and nano particles based on ultrasonic standing waves has attracted much attention for its high efficiency and simplicity of structure. This paper proposes a device that uses three modes of ultrasonic standing waves to continuously separate particles with positive acoustic contrast factor in microfluidics. Three modes of acoustic standing waves are used simultaneously in different parts of the microchannel. According to the different acoustic radiation force received by the particles, the particles are finally separated to the pressure node lines on both sides and the center of the microchannel. In this separation method, initial hydrodynamic focusing and satisfying various equilibrium constraints during the separation process are the key. Through numerical simulation, the resonance frequency of the interdigital transducer, the distribution of sound pressure in the liquid, and the relationship between the interdigital electrode voltage and the output sound pressure are obtained. Finally, the entire separation process in the microchannel was simulated, and the separation of the two particles was successfully achieved. This work has laid a certain theoretical foundation for the rapid diagnosis of diseases in practical applications.

Charge-Based Separation of Micro- and Nanoparticles.

Deterministic Lateral Displacement (DLD) is a label-free particle sorting method that separates by size continuously and with high resolution. By combining DLD with electric fields (eDLD), we show separation of a variety of nano and micro-sized particles primarily by their zeta potential. Zeta potential is an indicator of electrokinetic charge—the charge corresponding to the electric field at the shear plane—an important property of micro- and nanoparticles in colloidal or separation science. We also demonstrate proof of principle of separation of nanoscale liposomes of different lipid compositions, with strong relevance for biomedicine. We perform careful characterization of relevant experimental conditions necessary to obtain adequate sorting of different particle types. By choosing a combination of frequency and amplitude, sorting can be made sensitive to the particle subgroup of interest. The enhanced displacement effect due to electrokinetics is found to be significant at low frequency and for particles with high zeta potential. The effect appears to scale with the square of the voltage, suggesting that it is associated with either non-linear electrokinetics or dielectrophoresis (DEP). However, since we observe large changes in separation behavior over the frequency range at which DEP forces are expected to remain constant, DEP can be ruled out.

Charge-Based Separation of Micro- and Nanoparticles

Charge-Based Separation of Micro- and Nanoparticles

Separation of micro and sub-micro diamagnetic particles in dual ferrofluid streams based on negative magnetophoresis.

In the present study, we numerically demonstrate an approach for separation of micro and sub-micro diamagnetic particles in dual ferrofluid streams based on negative magnetophoresis. The dual streams are constructed by an intermediate sheath flow, after which the negative magnetophoretic force induced by an array of permanent magnets dominates the separation of diamagnetic particles. A simple and efficient numerical model is developed to calculate the motions of particles under the action of magnetic field and flow field. Effects of the average flow velocity, the ratio of sheath fluid flow to sample fluid flow, the number of the magnet pair as well as the position of magnet pair are investigated. The optimal parametric condition for complete separation is obtained through the parametric analysis, and the separation principle is further elucidated by the force analysis. The separation of smaller micro and sub-micro diamagnetic particles is finally demonstrated. This study provides an insight into the negative magnetophoretic phenomenon and guides the fabrication of feasible, low-cost diagnostic devices for sub-micro particle separation.

Separation of nanoparticles via surfing on chemical wavefronts.

The separation of micro and nanoscale colloids is a necessary step in most biological microassay techniques, and is a common practice in microchemical processing. Chemical waves are frequently encountered in biochemical systems driven far from equilibrium. Here, we put forward a strategy for separating small suspending colloids by means of their surfing on substrate chemical wavefronts. The colloids with catalytic activities sensitive to the substrates are activated to show self-propulsion and consequently exhibit a chemotactic response to the traveling wavefronts, which results in their spontaneous separation from the multicomponent complex mixture via self-diffusiophoresis. The dynamics of the process is analyzed through a particle-based simulation. In addition, it is found that separation can be carried out according to particle size. The mechanisms underpinning the chemical and physical separation processes are discussed, and the dependencies on the reaction rate constant and particle size are presented. The results may prove relevant for further experimental and theoretical studies of separation in complex active environments.

Effects of Pre-ozonation on Membrane Filtration of Oil-in-water Emulsions Using Different Polymeric (PES, PAN, PTFE) Ultrafilter Membranes

ABSTRACTEmulsified oily contaminants of wastewaters cannot be eliminated effectively by conventional treatments, but they pose significant risks both to the environment and to human health, therefore their efficient elimination is imperative. Membrane filtration is a promising technique for the effective purification of oil-in-water emulsions; however, the accumulation of hydrophobic contaminants on the membrane surface quickly leads to significant water flux reduction, which is a limiting factor of the economic utilization. In the present comparative study short-term ozonation was investigated as a suitable pre-treatment to achieve lower flux reduction during the separation of micro- or even nanoscale crude oil droplets by ultrafiltration with different membranes. Results confirmed that pre-ozonation modifies the surface charge (zeta-potential) of the oil droplets which resulted in the reduced accumulation of contaminants on the membrane surface and higher fluxes in the case of every investigated ultrafilter membranes: polyethersulfone (PES), polyacrylonitrile (PAN), polytetrafluoroethylene (PTFE). Filtration experiments were carried out using ultrapure and model groundwater matrices for a more thorough discussion of achievable advantages, and it was concluded that in the case of low ionic strength the PES membrane provided the highest flux; however, in the case of realistic water matrix (model groundwater) the application of acetone-conditioned PTFE ultrafilter membrane – combined with pre-ozonation – was much more beneficial. Overall, pre-ozonation decreased the total resistance in all cases; however, the reversibility of the measured filtration resistance and flux reduction was strongly dependent on both the matrix and the membrane surface material.

Shape-based separation of micro-/nanoparticles in liquid phases.

The production of particles with shape-specific properties is reliant upon the separation of micro-/nanoparticles of particular shapes from particle mixtures of similar volumes. However, compared to a large number of size-based particle separation methods, shape-based separation methods have not been adequately explored. We review various up-to-date approaches to shape-based separation of rigid micro-/nanoparticles in liquid phases including size exclusion chromatography, field flow fractionation, deterministic lateral displacement, inertial focusing, electrophoresis, magnetophoresis, self-assembly precipitation, and centrifugation. We discuss separation mechanisms by classifying them as either changes in surface interactions or extensions of size-based separation. The latter includes geometric restrictions and shape-dependent transport properties.

Peristome‐Mimetic Curved Surface for Spontaneous and Directional Separation of Micro Water‐in‐Oil Drops

AbstractSeparation of micro‐scaled water‐in‐oil droplets is important in environmental protection, bioassays, and saving functional inks. So far, bulk oil–water separation has been achieved by membrane separation and sponge absorption, but micro‐drop separation still remains a challenge. Herein we report that instead of the “plug‐and‐go” separation model, tiny water‐in‐oil droplets can be separated into pure water and oil droplets through “go‐in‐opposite ways” on curved peristome‐mimetic surfaces, in milliseconds, without energy input. More importantly, this overflow controlled method can be applied to handle oil‐in‐oil droplets with surface tension differences as low as 14.7 mN m−1 and viscous liquids with viscosities as high as hundreds centipoises, which markedly increases the range of applicable liquids for micro‐scaled separation. Furthermore, the curved peristome‐mimetic surface guides the separated drops in different directions with high efficiency.

Peristome-Mimetic Curved Surface for Spontaneous and Directional Separation of Micro Water-in-Oil Drops.

Separation of micro-scaled water-in-oil droplets is important in environmental protection, bioassays, and saving functional inks. So far, bulk oil-water separation has been achieved by membrane separation and sponge absorption, but micro-drop separation still remains a challenge. Herein we report that instead of the "plug-and-go" separation model, tiny water-in-oil droplets can be separated into pure water and oil droplets through "go-in-opposite ways" on curved peristome-mimetic surfaces, in milliseconds, without energy input. More importantly, this overflow controlled method can be applied to handle oil-in-oil droplets with surface tension differences as low as 14.7 mN m-1 and viscous liquids with viscosities as high as hundreds centipoises, which markedly increases the range of applicable liquids for micro-scaled separation. Furthermore, the curved peristome-mimetic surface guides the separated drops in different directions with high efficiency.

Inertial Impaction on MEMS Balance Chips for Real-Time Air Quality Monitoring

This paper reports on integration of microelectromechanical systems (MEMS) balance chips with aerosol inertial impactors for real-time monitoring of airborne particulate matter. Cascade inertial impactors have been extensively used for sampling and size separation of micro to nano-size airborne particles since they were first used in 1945. To introduce the real-time measurement capability to such tools, herein, MEMS resonator chips are employed as their impaction substrates. Dual-plate thermal-piezoresistive resonators (TPRs), that are shown to operate as promising mass balances, are integrated within a two-stage custom made aerosol impactor capable of size segregating particles down to a few tens of nanometers. Unlike cantilever-based microbalances or resonators operating in their bulk mode, TPRs provide uniform mass sensitivity over a big portion of their surface area. Upon deposition of airborne particles on the resonant sensors, the mass loading on each sensor and as a result the mass concentrations of size-segregated particles is measured in real-time. The air quality of different environments, including a class 10,000 cleanroom, was analyzed and monitored via the real-time impactor over a four day period. Comparison of the results with those of an optical particle counter demonstrates a clear correlation between the system response and the expected particle counts. Compared to existing optical particle counters, the proposed system offers the added advantage of detecting sub-100nm particles.

Evolutionary economics, organisational evolution, and behavioural approach: in search of commonalities

The overarching aim of the paper is to find the commonalities amongst evolutionary economics, organisational evolution, and behavioural approach and more specifically to conceptually clarify the extent to which the driving forces of organisational change can be explained by those fields. The aim has been realised through extensive literature studies and deductive referring. The key findings are as follows: 1) the separation of micro (individual) level from macro (organisational) level of analysing organisational behaviour requires a call for an integrative theory taking into account routine and non-routine organisational behaviour as the potential tool enabling an organisational change; 2) the behavioural theory of the firm seems to be well positioned to integrate constructs across levels as well as to integrate the phenomena inquired in evolutionary economics and organisational evolution fields since it stems from analysing individual decision-making along with process explanations for economically important firm decisions

Evolutionary economics, organisational evolution, and behavioural approach: in search of commonalities

The overarching aim of the paper is to find the commonalities amongst evolutionary economics, organisational evolution, and behavioural approach and more specifically to conceptually clarify the extent to which the driving forces of organisational change can be explained by those fields. The aim has been realised through extensive literature studies and deductive referring. The key findings are as follows: 1) the separation of micro (individual) level from macro (organisational) level of analysing organisational behaviour requires a call for an integrative theory taking into account routine and non-routine organisational behaviour as the potential tool enabling an organisational change; 2) the behavioural theory of the firm seems to be well positioned to integrate constructs across levels as well as to integrate the phenomena inquired in evolutionary economics and organisational evolution fields since it stems from analysing individual decision-making along with process explanations for economically important firm decisions

Propulsion mechanisms and applications of multiphysics- driven micro- and nanomotors

Multiphysics-driven synthetic micro/nanomotors can convert chemical or other types of energies, such as magnetic, electrical, photochemical, thermal, acoustic energies into mechanical energies in terms of motion and velocity. Significant efforts have been dedicated to preparing micro/nanomotors as well as the applications of micro/nanomotors. This paper provides a comprehensive review on the research for a large variety of micro/nanomotors recently investigated in China. Three types of propulsion mechanisms are proposed for multiphysics-driven synthetic micro/nanomotors, i.e., chemical propulsion, external-physical-fields propulsion and hybrid propulsion. It is shown that chemical propelled micro/ nanomotors can convert the chemical energy caused by the redox reactions into mechanical energy, such as concentration- gradient propelled micro/nanomotors, self-electrophoresis micro/nanomotors and bubble-propelled micro/nanomotors. Among the diverse chemical propelled micro/nanomotors, the micro/nanomotors prepared by rolled-up or eletrodeposition technique show a higher velocity and a more controllable motion. External-physical-fields propelled micro/nanomotors can transfer light, magnetic energy, ultrasonic energy into mechanical energy. There is no need to require any additional chemical fuel which is harmful to human body such as hydrogen peroxide, strong acid, alkaline, Br2, or I2 solutions, for the micro/nanomotors propelled by external-physical-fields. Therefore, it has better biocompatibility and broader applications than the chemical propelled micro/nanomotors. Hybrid propelled micro/nanomotors can combine the chemical propulsion mechanisms with external-physical-fields propulsion mechanisms simultaneously. The hybrid propelled micro/nanomotors not only can move in the chemical fuel, but also can be propelled by light, magnetism or ultrasonic energy. It has more powerful applicability and a broader application than that propelled by the other two propulsion mechanisms. Although the existed researches of micro/nanomotors are still of limitations, such as ambiguous propulsion mechanisms, low velocity, imprecise motion control and poor biocompatibility, the Chinese researchers have made significant progress and breakthroughs in recent years. The micro/nanomotors, which move autonomously in fluids, are studied for a growing number of applications that include targeted drug delivery, separation, biosensor, and fabrication of active biomimetic systems, environmental remediation and other emerging applications. The micro/ nanomotors can be used as adsorbent of microscale particle to achieve reversible swarming and separation of micro/ nanomotors, eliminate the pollutants in environment and the toxin in human body. In recent years, the micro/nanomotors can also be used as microscale sensor to measure micro-fluid viscosity, search and repair the microcracks. In addition, the micro/nanomotors can be applied for drug carrier to pick up and deliver the drug particles to targeted locations and can effectively control-release drug molecules to avoid drug accumulation. Nowadays, the micro/nanomotors also can be applied to control and assemble the microparticles and this technique is expected to be applied for biological single-cell analysis system. Although the micro/nanomotors can be applied in different fields, the real application of micro/ nanomotors is still far away to reach, especially to be used in human body. In conclusion, various propulsion mechanisms have been demonstrated in this review. Furthermore, typical applications in various fields are also presented. The prospects, challenges and future trends of the investigation on micro-and nanomotors are discussed. It is helpful for researches who are working in micro/nano motors research area as well as in engineering applications.

Micro-macro model for prediction of local temperature distribution in heterogeneous and two-phase media

Abstract Heat flow in heterogeneous media with complex microstructure follows tortuous path and therefore determination of temperature distribution in them is a challenging task. Two-scales, micro-macro model of heat conduction with phase change in such media was considered in the paper. A relation between temperature distribution on the microscopic level, i.e., on the level of details of microstructure, and the temperature distribution on the macroscopic level, i.e., on the level where the properties were homogenized and treated as effective, was derived. The expansion applied to this relation allowed to obtain its more simplified, approximate form corresponding to separation of micro- and macro-scales. Then the validity of this model was checked by performing calculations for 2D microstructure of a composite made of two constituents. The range of application of the proposed micro-macro model was considered in transient states of heat conduction both for the case when the phase change in the material is present and when it is absent. Variation of the effective thermal conductivity with time was considered and a criterion was found for which application of the considered model is justified.

Simultaneous separation and concentration of micro- and nano-particles by optically induced electrokinetics

This paper presents our work on the automated and parallel manipulation, separation, and concentration of micro- and nano-particles utilizing a hydrogenated, amorphous silicon (a-Si:H)-based optically induced electrokinetics (OEK) chip. A theoretical analysis and calculation of the crossover frequency spectrum characteristic of polystyrene beads is first presented. Then, we use different optically induced dielectrophoresis (ODEP) force directionalities, i.e., positive and negative components, to separate polystyrene beads with diameters of 10μm and 1μm, respectively. Furthermore, we have also demonstrated experimentally that polystyrene beads with three different diameters, i.e., 500nm, 1μm, and 10μm, can also be simultaneously separated and concentrated by combining different directionality and magnitudes of the ODEP force. We elucidated the dominate factors governing the operating regimes for rapid and simultaneous separation of micro-/nano-particles using OEK in this paper, and concluded that OEK is an extremely useful technology for the rapid sorting of micro-/nano-particles.

Front Cover: On‐chip control of magnetic particles (Phys. Status Solidi A 5/2012)

During the last years magnetic micro- and nanoparticles have emerged as powerful tools in the fields of cancer treatment, bioassays, contrast enhancement or labeling on the micron- and submicron-scale. Advances in controlling the dimensions, magnetic properties, and surface chemistry of particles have opened up various new approaches, particularly for lab-on-a-chip applications. These applications emphasize the need for tools to collect and handle magnetic particles in an efficient and reliable way. Optical and magnetic tweezers fulfill these requirements but are only applicable in a limited way to on-chip experiments. Recently, microstructured conducting wires have been used to collect and move magnetic micro- and nanoparticles in lab-on-a-chip approaches. A particularly versatile architecture is given by orthogonal layers of parallel microwires on a chip surface to induce highly localized magnetic fields. Rinklin et al. (pp. 871–874) investigate different current patterns for magnetic actuation and present simple yet efficient protocols for the collection and separation of micro- and nanoparticles without the necessity of external magnets. The cover image illustrates an exemplary collection and actuation experiment. To the left, the particles are collected from a homogeneous suspension. The particle cloud generated in this way can then be moved at the chip's surface as shown in the schematic and the corresponding image series.