Submicron-scale Particles Research Articles

Investigation on submicron particle separation and deflection using tilted-angle standing surface acoustic wave microfluidics

With the development of in vitro diagnostics, extracting submicron scale particles from mixed body fluids samples is crucial. In recent years, microfluidic separation has attracted much attention due to its high efficiency, label-free, and inexpensive nature. Among the microfluidic-based separation, the separation based on ultrasonic standing waves has gradually become a powerful tool. A microfluid environment containing a tilted-angle ultrasonic standing surface acoustic wave (taSSAW) field has been widely adapted and designed to separate submicron particles for biochemical applications. This paper investigated submicron particle defection in microfluidics using taSSAWs analytically. Particles with 0.1–1 μm diameters were analyzed under acoustic pressure, flow rate, tilted angle, and SSAW frequency. According to different acoustic radiation forces acting on the particles, the motion of large-diameter particles was more likely to deflect to the direction of the nodal lines. Decreasing the input flow rate or increasing acoustic pressure and acoustic wave frequency can improve particle deflection. The tilted angle can be optimized by analyzing the simulation results. Based on the simulation analysis, we experimentally showed the separation of polystyrene microspheres (100 nm) from the mixed particles and exosomes (30–150 nm) from human plasma. This research results can provide a certain reference for the practical design of bioparticle separation utilizing acoustofluidic devices.

Submicron Nonporous Silica Particles for Enhanced Separation Performance in pCEC.

Applications of submicron-scale particles are of rising interest in separation science due to their favorable surface-to-volume ratio and their fabrication of highly ordered structures. The uniformly dense packing beds in columns assembled from nanoparticles combined with an electroosmotic flow-driven system has great potential in a highly efficient separation system. Here, we packed capillary columns using a gravity method with synthesized nanoscale C18-SiO2 particles having diameters of 300-900 nm. The separation of small molecules and proteins was evaluated in the packed columns on a pressurized capillary electrochromatography platform. The run-to-run reproducibility regarding retention time and peak area for the PAHs using a column packed with 300 nm C18-SiO2 particles were less than 1.61% and 3.17%, respectively. Our study exhibited a systematic separation analysis of small molecules and proteins based on the columns packed with submicron particles combined with the pressurized capillary electrochromatography (pCEC) platform. This study may provide a promising analytical approach with extraordinary column efficiency, resolution, and speed for the separation of complex samples.

Nanoscale pore measurements in an all-solid-state lithium-ion battery with ultra-small-angle X-ray scattering (USAXS)

In a high performance all-solid-state lithium-ion battery (ASSLiB), lithium-ion should be smoothly transported to minimize overpotential. Nanoscale pores in the ASSLiB can inhibit ionic transportation; therefore, the pore structure should be measured and nanoscale pores should be prevented for high performance batteries. In this study, laboratory-scale ultra-small-angle X-ray scattering (USAXS) measurements are proposed to evaluate the nanoscale pores in ASSLiBs. The results measured with the USAXS are validated by comparing them with synchrotron radiation (SR) X-ray nanotomography data. The pore volumetric density distributions from the USAXS measurements are very close to those from SR X-ray nanotomography; this demonstrates that the nanoscale pores in ASSLiBs can be measured by USAXS. USAXS measurements of pore structures of solid electrolytes prepared from micron-scale and submicron-scale particles solid electrolyte (SE) reveal that the pore structure is not simply dependent on the SE particle size.

Direct Laser Writing for Deterministic Lateral Displacement of Submicron Particles

Emerging additive manufacturing (or “three-dimensional (3D) printing”) strategies offer the potential to vastly extend the capabilities of established microfluidic technologies. For example, the operational performance of “deterministic lateral displacement (DLD)” - a technique in which micro/nanoposts arrayed inside of a microfluidic channel enable passive transport of target suspended particles away from their initial flow streams - is based on geometric design variables, such as the gap spacing between the arrayed posts (G). For applications that involve DLD processing of submicron-scale particles (e.g., extracellular vesicles), however, achieving the requisite geometric control via conventional microfabrication protocols represents a technically challenging manufacturing hurdle. To bypass such barriers, here we explore the use of two-photon “direct laser writing (DLW)” for additively manufacturing DLD arrays capable of submicron particle handling. Studies of DLW fabrication conditions revealed that increasing the laser power from 22.5 mW to 27.5 mW significantly decreased G from 1.51±0.04 μm to 1.02±0.05 μm, respectively. Experimental microfluidic testing of 860 nm-in-diameter fluorescent particles within the DLW-printed DLD system revealed effective hydrodynamic railing of particles along the angled arrayed microposts, with a lateral displacement of 15.3±8.6 μm over a channel length of 500 μm. These results represent, to our knowledge, the first report of a 3D printed DLD system capable of processing submicron particles, thereby offering a promising foundation for DLW-enabled DLD-based biomedical applications.

Cavitation Assisted Production of Assemblies of Magnetic Nanoparticles of High Chemical Purity

A new method for magnetic nano- and submicron-scale particle fabrication is proposed. Magnetic particles of Fe73Co27 alloy were produced by a cavitation process directly into three different liquids: distilled water, benzyl alcohol and methyl methacrylate. The dependency between liquid viscosity and average particle size and size distributions are illustrated. The average particle size is found to be 224 nm in benzyl alcohol and 475 nm in methyl methacrylate. Also, assembly with a size of 20–80 nm was successfully separated from the poly-dispersed mixture obtained in distilled water. Fe73Co27 particles obtained by cavitation inherit the perfect crystal structure of the original macro-sample and possess a high value of the saturation magnetization, Ms = 242 emu/g. These particles can be applied for biomedical purposes and as a component of magneto–polymer composites.

Design of a 3D printed smartphone microscopic system with enhanced imaging ability for biomedical applications.

Portable, low-cost smartphone platform microscopic systems have emerged as a potential tool for imaging of various micron and submicron scale particles in recent years (Ozcan; Pirnstill and Coté; Breslauer etal.; Zhu etal.). In most of the reported works, it involves either the use of sophisticated optical set-ups along with a high-end computational tool for postprocessing of the captured images, or it requires a high-end configured smartphone to obtain enhanced imaging of the sample. Present work reports the working of a low-cost, field-portable 520× optical microscope using a smartphone. The proposed smartphone microscopic system has been designed by attaching a 3D printed compact optical set-up to the rear camera of a regular smartphone. By using cloud-based services, an image processing algorithm has been developed which can be accessed anytime through a mobile broadband network. Using this facility, the quality of the captured images can be further enhanced, thus obviating the need for dedicated computational tools for postprocessing of the images. With the designed microscopic system, an optical resolution ∼2 µm has been obtained. Upon postprocessing, the resolution of the captured images can be improved further. It is envisioned that with properly designed optical set-up in 3D printer and by developing an image processing application in the cloud, it is possible to obtain a low-cost, user-friendly, field-portable optical microscope on a regular smartphone that performs at par with that of a laboratory-grade microscope. LAY DESCRIPTION: With the ever-improving features both in hardware and software part, smartphone becomes ubiquitous in the modern civilised society with approximately 8.1 billion cell phone users across the world, and ∼40% of them can be considered as smartphones. This technology is undoubtedly the leading technology of the 21st century. Very recently, various researchers across the globe have utilised different sensing components embedded in the smartphone to convert it into a field-portable low-cost and user-friendly tool which can be used for different sensing and imaging purposes. By using simple optical components such as lens, pinhole, diffuser etc. and the camera of the smartphone, various groups have converted the phone into a microscopic imaging system. Again, by removing the camera lenses of the phone, holography images of microscopic particles by directly casting its shadows on the CMOS sensor on the phone has been demonstrated. The holographic images have subsequently been processed using the dedicated computational tool, and the original photos of the samples can be obtained. All the reported smartphone-based microscopic systems either suffer from relatively low field-of-view (FOV), resolution or it needs a high computational platform. Present work, demonstrate an alternative approach by which a reasonably good resolution (<2 µm) along with high optical magnification (520×) and a large FOV (150 µm) has been obtained on a regular smartphone. For postprocessing of the captured images an image processing algorithm has been developed in the cloud and the same can be accessed by the smartphone application, obviating the need of dedicated computational tool and a high-end configured smartphone for the proposed microscope. For the development of the proposed microscopic system, a simple optical set-up has been fabricated in a 3D printer. The set-up houses all the required optical components and the sample specimen with the 3D-printed XY stage, and it can be attached easily to the rear camera of the smartphone. Using the proposed microscopic system, enhanced imaging of USAF target and red blood cells have been successfully demonstrated. With the readily available optical components and a regular smartphone, the net cost involvement is significantly low (less than $250, including the smartphone). We envisioned that the designed system could be utilised for point-of-care diagnosis in resource-poor settings where access to the laboratory facilities is very limited.

Synthesis and characterization of environmentally friendly BiVO4 yellow pigment by non-hydrolytic sol-gel route

Monoclinic bismuth vanadate (m-BiVO4) yellow pigments were synthesized by non-hydrolytic sol-gel (NHSG) route without any surfactants. The presence of Bi–O–V band in the sol and xerogel, indicates that the excellent atomic scale homogeneity could be reached. It is beneficial to achieve high purity m-BiVO4 phase and submicron scale particles (738 nm) with homogenous distribution at low temperature (400 °C), resulting in a brilliant yellow hue (b* = 71.18, hab = 89.73). These pigments have better chromatic performance than previously reported and commercially available BiVO4 yellow pigments. Meanwhile, the cytotoxicity of the pigment was tested in Mus musculus skin melanoma cells, and showed nontoxic for human cells, indicating its potential application in the high quality paints for automotive and architectural finishes.

Convolutional neural networks automate detection for tracking of submicron-scale particles in 2D and 3D

Particle tracking is a powerful biophysical tool that requires conversion of large video files into position time series, i.e., traces of the species of interest for data analysis. Current tracking methods, based on a limited set of input parameters to identify bright objects, are ill-equipped to handle the spectrum of spatiotemporal heterogeneity and poor signal-to-noise ratios typically presented by submicron species in complex biological environments. Extensive user involvement is frequently necessary to optimize and execute tracking methods, which is not only inefficient but introduces user bias. To develop a fully automated tracking method, we developed a convolutional neural network for particle localization from image data, comprising over 6,000 parameters, and used machine learning techniques to train the network on a diverse portfolio of video conditions. The neural network tracker provides unprecedented automation and accuracy, with exceptionally low false positive and false negative rates on both 2D and 3D simulated videos and 2D experimental videos of difficult-to-track species.

Physicochemical conditions and properties of particles in urban runoff and rivers: Implications for runoff pollution

In this study, to gain an improved understanding of the fate and fractionation of particle-bound pollutants, we evaluated the physicochemical conditions and the properties of particles in rainwater, urban runoff, and rivers of Yixing, a city with a large drainage density in the Taihu Lake Basin, China. Road runoff and river samples were collected during the wet and dry seasons in 2015 and 2016. There were significant differences between the physicochemical conditions (pH, oxidation-reduction potential (ORP), and electroconductivity (EC)) of rainwater, runoff, and rivers. The lowest pH and highest ORP values of rainwater provide the optimal conditions for leaching of particle-bound pollutants such as heavy metals. The differences in the physicochemical conditions of the runoff and rivers may contribute to the redistribution of pollutants between particulate and dissolved phases after runoff is discharged into waterways. Runoff and river particles were mainly composed of silt and clay (<63 μm, 88.3%–90.7%), and runoff particles contained a higher proportion of nano-scale particles (<1 μm) but a lower proportion of submicron-scale particles (1–16 μm) than rivers. The ratio of turbidity to TSS increased with the proportion of fine particles and was associated with the accumulation of pollutants and settling ability of particles, which shows that it can be used as an index when monitoring runoff pollution.

Analysis of optical scattering of micro-nano particles

The micro-nano-scale science is rapidly developing. In order to study the properties of micro-nano-scale particles by the optical method, we discuss the scattering effects of sub-micrometer wires and sub-micrometer balls on photo-electromagnetic wave in this paper. For the optical scattering of micro-nano-scale particles, the scattering particle size can meet the Mie scattering conditions compared with the incident light wavelength, that is to say, the scatterer and the incident wavelength have comparable size. In this article, the analysis results are clearly displayed in the form of simulation graphs obtained by the Matlab numerical simulation. The Mie scattering analysis method can be used for discussing the scattering of electromagnetic waves in the cases of layered particles which meet the size requirements and any number of scattering particles. Multi-particle scattering is analyzed to investigate the effects of scatterers at different positions on the scattering. By analyzing the differential scattering cross section and the electromagnetic field distribution of near-field scattering related to the scattering light field, we obtain the variation trend of the scattering light field with scattering angle and the effects of various factors on the scattering light field, including the polarization of incident wave, the size of the scatterer, the structure of scattering particles, the number of particles, the number of scattering particles, and some hidden factors such as the relative refractive index of scatterer and surrounding medium. The scientific significance of the paper is reflected through the fact that the sub-micron scale particle can be used as a sensor of detecting the displacement, which can be realized by optical means. So it has a certain reference value for studying the influence of particle own characteristic on the scattering light, thereby rendering the optical readout of the mechanical displacement very accurate. The obtained results have a guiding significance for studying the optical detection of mechanical vibrations of sub-micron wires.

Demands, Potentials, and Economic Aspects of Thermal Spraying with Suspensions: A Critical Review

Research and development work for about one decade have demonstrated many unique thermal spray coating properties, particularly for oxide ceramic coatings by using suspensions of fine powders as feedstock in APS and HVOF processes. Some particular advantages are direct feeding of fine nano- and submicron-scale particles avoiding special feedstock powder preparation, ability to produce coating thicknesses ranging from 10 to 50 µm, homogeneous microstructure with less anisotropy and lower surface roughness compared to conventional coatings, possibility of retention of the initial crystalline phases, and others. This paper discusses the main aspects of thermal spraying with suspensions which have been taken into account in order to produce these coatings on an economical way. The economic efficiency of the process depends on the availability of suitable additional system components (suspension feeder, injectors), on the development and handling of stable suspensions, as well as on the high process stability for acceptance at industrial scale. Special focus is made on the development and processability of highly concentrated water-based suspensions. While costs and operational safety clearly speak for use of water as a liquid media for preparing suspensions on an industrial scale, its use is often critically discussed due to the required higher heat input during spraying compared to alcoholic suspensions.

Rapid and simple electrochemical detection of morphine on graphene–palladium-hybrid-modified glassy carbon electrode

A hybrid of reduced graphene oxide-palladium (RGO-Pd) nano- to submicron-scale particles was simultaneously chemically prepared using microwave irradiation. The electrochemical investigation of the resulting hybrid was achieved using cyclic voltammetry and differential pulse voltammetry. RGO-Pd had a higher current response than unmodified RGO toward the oxidation of morphine. Several factors that can affect the electrochemical response were studied, including accumulation time and potential, Pd loading, scan rate, and pH of electrolyte. At the optimum conditions, the concentration of morphine was determined using differential pulse voltammetry in a linear range from 0.34 to 12 μmol L(-1) and from 14 to 100 μmol L(-1), with detection limits of 12.95 nmol L(-1) for the first range. The electrode had high sensitivity toward morphine oxidation in the presence of dopamine (DA) and of the interference compounds ascorbic acid (AA) and uric acid (UA). Electrochemical determination of morphine in a spiked urine sample was performed, and a low detection limit was obtained. Validation conditions including reproducibility, sensitivity, and recovery were evaluated successfully in the determination of morphine in diluted human urine.

Redispersing and stabilizing agglomerates in an annular-gap high shear disperser

Abstract Unwanted agglomeration of submicron and nanoscale particles is an important problem. For many applications in particle technology, the desired form of particle products (produced from wet grinding or precipitation processes) is a stable primary particle suspension. Prior to use, a redispersion of agglomerated or aggregated (connected by solid bridges) particles is often necessary. Spontaneous agglomeration and reagglomeration processes happen for not sufficiently stabilized nano- and submicron scale particles. A successful redispersion into primary particles requires that the primary particle surfaces be stabilized simultaneously against reagglomeration by surfactants or surface charges. The redispersion of micron-sized agglomerates in a turbulent shear field of an annular-gap disperser is described in this investigation. The redispersion kinetic and the maximum agglomerate size were measured and used to find a function for the agglomerate strength in shear fields.

Self-assembling nanoparticles for intra-articular delivery of anti-inflammatory proteins

Intra-articular delivery of therapeutics to modulate osteoarthritis (OA) is challenging. Delivery of interleukin-1 receptor antagonist (IL-1Ra), the natural protein inhibitor of IL-1, to modulate IL-1-based inflammation through gene therapy or bolus protein injections has emerged as a promising therapy for OA. However, these approaches suffer from rapid clearance and reduced potency over time. Nano/microparticles represent a promising strategy for overcoming the shortcomings of intra-articular drug delivery. However, these delivery vehicles are limited for delivery of protein therapeutics due to their hydrophobic character, low drug loading efficiency, and harsh chemical conditions during particle processing. We designed a new block copolymer that assembles into submicron-scale particles and provides for covalently tethering proteins to the particle surface for controlled intra-articular protein delivery. This block copolymer self-assembles into 300 nm-diameter particles with a protein tethering moiety for surface covalent conjugation of IL-1Ra protein. This copolymer particle system efficiently bound IL-1Ra and maintained protein bioactivity in vitro. Furthermore, particle-tethered IL-1Ra bound specifically to target synoviocyte cells via surface IL-1 receptors. Importantly, IL-1Ra nanoparticles inhibited IL-1-mediated signaling to equivalent levels as soluble IL-1Ra. Finally, the ability of nanoparticles to retain IL-1Ra in the rat stifle joint was evaluated by in vivo imaging over 14 days. IL-1Ra-tethered nanoparticles significantly increased the retention time of IL-1Ra in the rat stifle joint over 14 days with enhanced IL-1Ra half-life (3.01 days) compared to that of soluble IL-1Ra (0.96 days) and without inducing degenerative changes in cartilage structure or composition.

A microfluidic spiral for size-dependent fractionation of magnetic microspheres

Magnetic microspheres (MMS) are useful tools for a variety of medical and pharmaceutical applications. Typically, commercially manufactured MMS exhibit broad size distributions. This polydispersity is problematic for many applications. Since the direct synthesis of monodisperse MMS is often fraught with technical challenges, there is considerable interest in and need associated with the development of techniques for size-dependent fractionation of MMS. In this study we demonstrated continuous size-dependent fractionation of sub-micron scale particles driven by secondary (Dean effect) flows in curved microfluidic channels. Our goal was to demonstrate that such techniques can be applied to MMS containing superparamagnetic nanoparticles. To achieve this goal, we developed and tested a microfluidic chip for continuous MMS fractionation. Our data address two key areas. First, the densities of MMS are typically in the range 1.5–2.5g/cm3, and thus they tend be non-neutrally buoyant. Our data demonstrate that efficient size-dependent fractionation of MMS entrained in water (density 1g/cm3) is possible and is not significantly influenced by the density mismatch. In this context we show that a mixture comprising two different monodisperse MMS components can be separated into its constituent parts with 100% and 88% success for the larger and smaller particles, respectively. Similarly, we show that a suspension of polydisperse MMS can be separated into streams containing particles with different mean diameters. Second, our data demonstrate that efficient size-dependent fractionation of MMS is not impeded by magnetic interactions between particles, even under application of homogeneous magnetic fields as large as 35kA/m. The chip is thus suitable for the separation of different particle fractions in a continuous process and the size fractions can be chosen simply by adjusting the flow velocity of the carrier fluid. These facts open the door to size dependent fractionation of MMS.

Simultaneous sizing and electrophoretic mobility measurement of sub‐micron particles using Brownian motion

The size and surface chemistry of micron scale particles are of fundamental importance in studies of biology and air particulate pollution. However, typical electrophoretic measurements of these and other sub-micron scale particles (300 nm-1 μm) cannot resolve size information within heterogeneous mixtures unambiguously. Using optical microscopy, we monitor electrophoretic motion together with the Brownian velocity fluctuations - using the latter to measure size by either the Green-Kubo relation or by calibration from known size standards. Particle diameters are resolved to ±12% with 95% confidence. Strikingly, the size resolution improves as the particle size decreases due to the increased Brownian motion. The sizing ability of the Brownian assessed electrophoresis method described here complements the electrophoretic mobility resolution of the traditional CE.

多層カーボンナノチューブ製造工場における気中粒子の測定及び炭素分析 1

In order to assess the exposure risks of multiwall carbon nanotubes (MWCNT) for packing workers, we carried out real-time monitoring in the two types of packing facilities of MWCNT, and exposure measurements for the packing workers. In the real-time monitoring, a scanning mobility particle sizer (SMPS) and an optical particle counter (OPC) were used to measure nanoscale particles and sub-micron/micron scale particles, respectively. A personal sampler with PM 4.0 was used to measure the personal exposures in the packing facilities. One of the packing facilities is manually operated and the other is automated. The concentrations of airborne dust in both facilities were almost the same as each other at 0.24 mg/m(3) (total dust). However, the results of personal exposure measurements were quite different between the two facilities. The exposure concentrations of workers in the manually and automated operations were 2.39/0.39 (total/respirable) mg/m(3) and 0.29/0.08 (total/respirable) mg/m(3), respectively. From the time series study, submicron scale particles were released into the workplace air when the CNT products were put into temporary container bags from a hopper and manually packed into shipping bags. However, the task-related nanoscale particle release was not observed. The manual packing operation is one of the "hot spots" in MWCNT production facilities, and automation brings much improvement to reduce MWCNT exposure.

Preparation of functionalized nanoporous carbons for uranium loading

Ordered nanoporous carbons (CMK-3) with submicron-scale particle size were functionalized with carboxymethylated polyethyleneimine (CMPEI) as a new uranium loading material to increase uranium adsorption capacity, and characterized by Fourier transform-infrared spectroscopy (FT-IR) and powder X-ray diffraction (XRD). The adsorption isotherm of uranyl ions on the functionalized carbons was examined and evaluated using the Langmuir adsorption isotherm model. It was found that the adsorption of uranyl ions on the functionalized carbons follows the Langmuir isotherm model. The maximum uranium adsorption capacity of the adsorbent by the Langmuir model was calculated to be 151.5mgU/g adsorbent. The loading stability of uranium on the adsorbent was examined at pH 4. It was observed that about 30% of uranium was released from CMPEI/CMK-3 within a day, however, uranium contents almost linearly decreased with a low desorption rate from 1 to 20 days.

Preparation and characterization of mesoporous carbon-supported Pt nanocatalyst and its stability under strong acidic solutions

Pt/C catalyst was prepared by the formic acid reduction method (FARM) using mesoporous carbon supports with submicron-scale particle size, which was synthesized by the nano-replication technique using mesoporous silica (MSU-H) as templates. The average size of the Pt particles, calculated from the Pt(111) peak by Scherrer equation, was found to be 3.3nm. The chemical stabilities of Pt/C catalysts and polymer-coated Pt/C catalysts were examined in distilled water and in strong acidic solutions such as H2SO4 and HClO4. The release amount of Pt in distilled water was found to be at trace levels (<3ppb), which is close to the detection limits of ICP-AES. However, the Pt release greatly increased with time in both H2SO4 and HClO4 solutions and reached a few percent levels in a week. On the other hand, a PVP/PEI-coated Pt/C catalyst showed much better stability that the Pt release was about 0.5% in 3M HClO4 for a week, compared with that of a pristine Pt/C catalyst.

Application of polymer-modified nanoporous silica to adsorbents of uranyl ions

The surface modification of nanoporous silicas (MSU-H) of submicron-scale particle size with polyethyleneimine (PEI), polyacrylic acid (PAA), and carboxymethylated polyethyleneimine (CMPEI) was carried out for the extraction of uranyl ions. Adsorption behaviors of uranyl ions onto the polymer-modified silicas, denoted as PEI/MSU-H, PAA/MSU-H and CMPEI/MSU-H, were examined in batch experiments. In 0.05mM UO22+ solution, it was found that the nearly complete removal of uranyl ions can be achieved by the CMPEI-modified MSU-H (CMPEI/MSU-H). Especially, the CMPEI/MSU-H exhibited significantly high distribution coefficient value (Kd=2.30×106). In concentrated UO22+ solution (ca. 1mM), uranium-uptake capacities onto the three polymer-modified nanoporous silicas were in the following order: CMPEI/MSU-H>PAA/MSU-H>PEI/MSU-H. It is noteworthy that CMPEI/MSU-H showed excellent uranium-uptake capacity (124mg-U/g-adsorbent), based on the total weight of polymer and silica. In addition, the loading stability of uranium on the adsorbent was examined with time. It was observed that about 15% of uranium was discharged from CMPEI/MSU-H in a day and additional 5% uranium was released with a relatively slow desorption rate in 12 days.