Microns In Diameter Research Articles

Hydrothermal formation of fibrous mineral structures: The role on strength and mode of failure

Studying the mechanisms that control the rheology of rocks and geomaterials is crucial as much for predicting geological processes as for functionalizing geomaterials. That requires the understanding of how structural arrangements at the micro and nano scale control the physical and mechanical properties at the macroscopic scale. This is an area of rock physics still in its infancy. In this paper, we focus the attention on the formation of cementitious phases made of micro- and nano-scale fibrous structures, and the controls of the arrangement of these phases on mechanical properties. We use hydrothermal synthesis, and the properties of hydrothermal water, to promote the growth of fibrous mineral phases having nano-size diameter and length of a few microns, creating disordered and entangled mats of fibrous bundles as those found in natural samples. We draw inferences from structural microscopy to inform a statistical model that establishes an interdependence between structural parameters of fibrous structures and bulk mechanical response. Structural parameters include number and length of fibers, spatial orientation, and fraction of fibrous threads bearing the load. Mechanical properties include strength and mode of failure. Results show that as the fibrous microstructure evolves from ordered and aligned to disordered and entangled, the mechanical response of the fibrous composite transitions from a brittle to ductile behavior. Furthermore, the disordered and entangled microstructure exhibits lower strength at failure though strength increases as the number of fibers within the microstructure increases. Finally, the longer the entangled fiber, the larger the strain that the matrix can accommodate. The value of this study lies in further understanding fault healing through hydrothermal fluids and how the physical properties of fibrous microstructures resulting from it control brittle-ductile transitions, and possibly, slow slip events along subduction zones.

Influence of Air Pollutants on the Disease Activity and Quality of Life in Rheumatoid Arthritis, an Iranian Observational Longitudinal Study.

Environmental exposures and genetic predisposition interactions may result in autoimmune rheumatic diseases. This study aimed to determine the effect of outdoor air pollutants on the activity of rheumatoid arthritis (RA) in a longitudinal follow-up. We longitudinally studied 50 patients with RA bimonthly over 6 months in Mashhad, one of the most polluted cities in Iran. Disease activity and health-related quality of life (HRQoL) were examined according to the disease activity score (DAS28ESR), health assessment questionnaires (HAQ), physical health component summary (PCS), and visual analogue scale (VAS) criteria. The outdoor air pollutant was measured by monitoring the average concentration of nitrogen oxide (NO), carbon monoxide (CO), O2 level, Sulfur dioxide (SO2), and some particles less than 10 and 2.5 micrometers in diameter (PM <10 µm, PM <2.5 µm). The temperature and humidity levels were also measured. The univariate and multivariate statistical analyses were used for data analysis and the role of confounding factors was determined using the generalized estimation equation method. Statistical analysis indicated a significant increase of the DAS28ESR (B = 0.04 [0.08]; P = 0.01) and VAS (B = 4.48 [1.73]; P = 0.01) by CO concentration. Moreover, a number of polluted days increased the VAS in patients. In addition, other air pollutants, temperature, and humidity were not affected significantly by the DAS28ESR and quality of life indexes by considering confounders such as medications, age, and job. Based on our findings, CO concentration was the only effective outdoor air pollutant that could increase RA disease activity. In addition, CO concentration and the number of polluted days make patients feel more ill. As the role of indoor air pollutants is highly important, further research on this critical topic is required to establish the role of air pollution on RA disease activity.

Direct 3D-printed CdSe quantum dots via scanning micropipette.

The micropipette, pencil-shaped with an aperture diameter of a few micrometers, is a potentially promising tool for the three-dimensional (3D) printing of individual microstructures based on its capability to deliver low volumes of nanomaterial solution on a desired spot resulting in micro/nanoscale patterning. Here, we demonstrate a direct 3D printing technique in which a micropipette with a cadmium selenide (CdSe) quantum dot (QD) solution is guided by an atomic force microscope with no electric field and no piezo-pumping schemes. We define the printed CdSe QD wires, which are a composite material with a QD-liquid coexistence phase, by using photoluminescence and Raman spectroscopy to analyze their intrinsic properties and additionally demonstrate a means of directional falling.

Investigations of PM2.5 Long-term Exposure and Subclinical Atherosclerosis in Women: An Overview

Background/Aim Evidence demonstrates that coronary artery calcification (CAC) is a biological marker for cardiovascular disease (CVD) risk prediction. Acute cardiovascular effects of temporary and chronic environmental particle exposures sensitive to ≤2.5 micrometers in diameter (here termed “PM2.5”) have been well-studied. However, there is less information on the long-term effects of PM2.5 exposures on the earlier pre-clinical stage of CVD, especially in women (in whom it is also established experience frequent cardiovascular late- and under-diagnoses). This phase of pre-diagnosis pathological activity is classified as subclinical atherosclerosis (SCA) unless and until a patient meets established clinical diagnostic criteria. In this systematic review, we summarize reported associations of long-term PM2.5 and SCA exposure, with investigators placing an emphasis on gender differences in any documented associations. Methods We conducted a comprehensive literature review for articles published from 2007 to 2022 that reported associations of long-term PM2.5 and SCA and evaluated each study with areas of particular focus including study designs, populations at risk, and exposure measures. Results Investigations representing four cohorts yielded equivocal findings related to long-term PM2.5 exposure and CAC. Three cohorts reported positive associations between long-term PM2.5 and CAC development/progression. Two studies supported a strongly positive associations among women or postmenopausal women for PM2.5 on CAC. Studies, however, evaluating PM2.5 exposure associations with carotid intima-media thickness (another biomarker of SCA), reflect increases in both men and women with ↑ PM2.5 levels but reporting no gender differences in PM2.5 exposure and this measure of SCA. Conclusion Our study identifies important gaps in current knowledge synthesis including different methods of PM2.5 estimation and linkage, a lack of consensus of what constitutes long-term air pollution, and the selection of important covariates and intermediate variables. Our aim is to outline best practices going forward in the investigation of PM2.5 long-term exposure and SCA in women

An Investigation of Mechanical Properties of Recycled Carbon Fiber Reinforced Ultra-High-Performance Concrete.

Carbon fiber-reinforced concrete as a structural material is attractive for civil infrastructure because of its light weight, high strength, and resistance to corrosion. Ultra-high performance concrete, possessing excellent mechanical properties, utilizes randomly oriented one-inch long steel fibers that are 200 microns in diameter, increasing the concrete's strength and durability, where steel fibers carry the tensile stress within the concrete similar to traditional rebar reinforcement and provide ductility. Virgin carbon fiber remains a market entry barrier for the high-volume production of fiber-reinforced concrete mix designs. In this research, the use of recycled carbon fiber to produce ultra-high-performance concrete is demonstrated for the first time. Recycled carbon fibers are a promising solution to mitigate costs and increase sustainability while retaining attractive mechanical properties as a reinforcement for concrete. A comprehensive study of process structure-properties relationships is conducted in this study for the use of recycled carbon fibers in ultra-high performance concrete. Factors such as pore formation and poor fiber distribution that can significantly affect its mechanical properties are evaluated. A mix design consisting of recycled carbon fiber and ultra-high-performance concrete was evaluated for mechanical properties and compared to an aerospace-grade and low-cost commercial carbon fiber with the same mix design. Additionally, the microstructure of concrete samples is evaluated non-destructively using high-resolution micro X-ray computed tomography to obtain 3D quantitative spatial pore size distribution information and fiber clumping. This study examines the compression, tension, and flexural properties of recycled carbon fibers reinforced concrete considering the microstructure of the concrete resulting from fiber dispersion.

Deep Learning Based Air Quality Prediction: A Case Study for London

Although states take various measures to prevent air pollution, air pollutants continue to exist as an important problem in the world. One air pollutant that seriously affects human health is called PM2.5 (particles smaller than 2.5 micrometers in diameter). These particles pose a serious threat to human health. For example, it can penetrate deep into the lung, irritate and erode the alveolar wall and consequently impair lung function. From this, the event PM2.5 prediction is very important. In this study, PM2.5 prediction was made using 12 models, namely, Decision Tree (DT), Extra Tree (ET), k-Nearest Neighbourhood (k-NN), Linear Regression (LR), Random Forest (RF), Support Vector Machine (SVM), Extreme Gradient Boosting (XGBoost), Multi-Layer Perceptron (MLP), Convolutional Neural Network (CNN), Recurrent Neural Network (RNN), Gated Recurrent Unit (GRU), and Long Short-Term Memory (LSTM) models. The LSTM model developed according to the results obtained achieved the best result in terms of MSE, RMSE, MAE, and R2 metrics.

Predicting the Structural Colors of Films of Disordered Photonic Balls

Photonic balls are spheres tens of micrometers in diameter containing assemblies of nanoparticles or nanopores with a spacing comparable to the wavelength of light. When these nanoscale features are disordered, but still correlated, the photonic balls can show structural color with low angle-dependence. Their colors, combined with the ability to add them to a liquid formulation, make photonic balls a promising new type of pigment particle for paints, coatings, and other applications. However, it is challenging to predict the color of materials made from photonic balls because the sphere geometry and multiple scattering must be accounted for. To address these challenges, we develop a multiscale modeling approach involving Monte Carlo simulations of multiple scattering at two different scales: we simulate multiple scattering and absorption within a photonic ball and then use the results to simulate multiple scattering and absorption in a film of photonic balls. After validating against experimental spectra, we use the model to show that films of photonic balls scatter light in fundamentally different ways than do homogeneous films of nanopores or nanoparticles, because of their increased surface area and refraction at the interfaces of the balls. Both effects tend to sharply reduce color saturation relative to a homogeneous nanostructured film. We show that saturated colors can be achieved by placing an absorber directly in the photonic balls and mitigating surface roughness. With these design rules, we show that photonic-ball films have an advantage over homogeneous nanostructured films: their colors are even less dependent on the angle.

Unprecedented Triboelectric Effect of Lignin on Enhancing the Electrical Outputs of Natural-Rubber-Based Triboelectric Nanogenerators (TENGs)

Because of a lack of electron donor/acceptor groups, TENGs fabricated from natural rubber (NR) usually produce low electrical outputs. The present study demonstrated that the electrical outputs of NR TENGs could be enhanced by the presence of lignin. Lignin with an unanticipated triboelectric property became a triboelectric active material upon subjecting to ultrasound in a basic solution. Physically, lignin irradiated with ultrasound would undergo particle size reduction from tens of micrometers down to a micrometer in diameter, leading to an increase of interfacial area for triboelectric charge generation. Accompanying the size reduction was a partial depolymerization of lignin arising from the chemical bond cleavage via the nucleophilic attack of hydroxide ions. This event caused an increase of polar functional groups on lignin that benefited the charge generation and transfer. TENGs from the NR/lignin composite generated a power output density up to 500% larger than that produced from NR TENG. However, NR/lignin TENGs suffered from the aggregation of lignin leading to a compromise of the electrical outputs. Therefore, NR was grafted with polyacrylamide (NR-g-PAM) to inhibit lignin aggregation as well as to promote an even distribution of lignin particles in the NR matrix. As a result, NR-g-PAM/lignin TENG was capable of enhancing the power output density to 260 and 1300% compared with that of NR/lignin and NR TENGs, respectively.

In-Capillary Photodeposition of Glyphosate-Containing Polyacrylamide Nanometer-Thick Films.

The present research reports on in-water, site-specific photodeposition of glyphosate (GLP)-containing polyacrylamide (PAA-GLP) nanometer-thick films (nanofilms) on an inner surface of fused silica (fused quartz) microcapillaries presilanized with trimethoxy(octen-7-yl)silane (TMOS). TMOS was chosen because of the vinyl group presence in its structure, enabling its participation in the (UV light)-activated free-radical polymerization (UV-FRP) after its immobilization on a fused silica surface. The photodeposition was conducted in an aqueous (H2O/ACN; 3:1, v/v) solution, using UV-FRP (λ = 365 nm) of the acrylamide (AA) functional monomer, the N,N'-methylenebis(acrylamide) (BAA) cross-linking monomer, GLP, and the azobisisobutyronitrile (AIBN) UV-FRP initiator. Acetonitrile (ACN) was used as the porogen and the solvent to dissolve monomers and GLP. Because of the micrometric diameters of microcapillaries, the silanization and photodeposition procedures were first optimized on fused silica slides. The introduction of TMOS, as well as the formation of PAA and PAA-GLP nanofilms, was determined using atomic force microscopy (AFM), scanning electron microscopy with energy-dispersive X-ray (SEM-EDX) spectroscopy, and confocal micro-Raman spectroscopy. Particularly, AFM and SEM-EDX measurements determined nanofilms' thickness and GLP content, respectively, whereas in-depth confocal (micro-Raman spectroscopy)-assisted imaging of PAA- and PAA-GLP-coated microcapillary inner surfaces confirmed the successful photodeposition. Moreover, we examined the GLP impact on polymer gelation by monitoring hydration in a hydrogel and a dried powder PAA-GLP. Our study demonstrated the usefulness of the in-capillary micro-Raman spectroscopy imaging and in-depth profiling of GLP-encapsulated PAA nanofilms. In the future, our simple and inexpensive procedure will enable the fabrication of polymer-based microfluidic chemosensors or adsorptive-separating devices for GLP detection, determination, and degradation.

Investigation of PM2.5-induced carcinogenic effects through mediation of ErbB family based on DNA methylation and transcriptomics analysis by a lung-mimicking microfluidic platform

Fine particle (PM2.5, less than 2.5 micrometers in diameter) is regarded as a harmful carcinogen. However, the molecular mechanisms of the carcinogenic effects of ambient fine particles have not been fully elucidated, and therapeutic options to address this major public health challenge are lacking. Here, we present global gene-specific DNA methylation and transcriptomic (RNA-Seq) analyses after HBE cells were exposed to fine particles on a portable, small, and all-in-one organ-level lung-mimicking air-liquid interface exposure (MALIE) microfluidic platform. A series of cancer-related signal transduction pathways were activated. ErbB1, ErbB2, and ErbB3 gene expression altered by fine particle exposure was the result of changes in the cellular DNA methylome. The protein expression of ErbB family was inhibited by drugs and could regulate downstream Grb2/Raf pathway and Akt/MDM2 pathway. All of the above results indicated that ErbB family may be promising drug targets for air pollution-related diseases and that inhibitor drugs can be used as therapeutic options to treat these diseases.

Cu Nanowires and Nanoporous Ag Matrix Fabricated through Directional Solidification and Selective Dissolution of Ag-Cu Eutectic Alloys.

Cu nanowires and a nanoporous Ag matrix were fabricated through directional solidification and selective dissolution of Ag-Cu eutectic alloys. Ag-39.9at.%Cu eutectic alloys were directionally solidified at growth rates of 14, 25, and 34 μm/s at a temperature gradient of 10 K/cm. The Cu phase in the Ag matrix gradually changed from lamellar to fibrous with an increase in the growth rate. The Ag matrix phase was selectively dissolved, and Cu nanowires of 300-600 nm in diameter and tens of microns in length were prepared in 0.1 M borate buffer with a pH of 9.18 at a constant potential of 0.7 V (vs. SCE). The nanoporous Ag matrix was fabricated through selective dissolution of Cu fiber phase in 0.1 M acetate buffer with a pH of 6.0 at a constant potential of 0.5 V (vs. SCE). The diameter of Ag pores decreased with increasing growth rate. The diameter and depth of Ag pores increased when corrosion time was extended. The depth of the pores was 30 μm after 12 h.

InGaAsP/InP Geiger-Mode Avalanche Photodiode Towards Sub-kHz Dark Count Rate at 20% Photon Detection Efficiency

Geiger-mode InGaAsP/InP single photon avalanche photodiode (SPAD) with a low dark count rate (DCR) of 870 Hz at a photon detection efficiency (PDE) of 20% at 1064 nm is achieved for a 40 micron diameter device at −30 °C. Extensively optimized and accurately controlled shallow/deep two-step pn junction and doping profiles are identified to play decisive roles for the performance improvement. While a state-of-the-art specific detectivity of 1.4×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">14</sup> cm·Hz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2</sup> /W is realized for the optimized SPAD, a temperature coefficient of the breakdown voltage (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">br</sub> ) of 139 mV/K, a dark current of 200 pA at 90%V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">br</sub> and a timing jitter of 280 ps at 20% PDE are also simultaneously attained. Thermal activation energies of approximate 0.5 eV are observed for both the dark current and the DCR at 253–293 K, indicates the dominant source of dark carriers is the mid-gap defect trapping states-related tunneling in the InGaAsP absorber.

Electrically conducting films prepared from graphite and lignin in pure water.

In this study, we present electrically conducting self-standing graphite films consisting of lignin derivatives extracted by simultaneous enzymatic saccharification and comminution (SESC). Sonication of graphite powder in the presence of SESC lignin and pure water allows dispersion of the SESC-lignin-attached graphite without addition of other chemicals. The SESC-lignin-attached graphite having a diameter of several micrometers can be used as a surface electroconductive coating and molded into self-standing films by drying. The SESC-lignin-attached graphite film exhibits higher conductivity (∼2,075 S/cm) than graphite-based composites consisting of ordinary lignin derivatives. Manufacturing self-standing films of micrometer-sized graphite using SESC lignin enables high electrical conductivity of the SESC-lignin-attached graphite film. The size of the SESC-lignin-attached graphite is proportional to the conductivity of the film. The SESC-lignin-attached graphite also acts as an antiplasticizer and a conductive filler for polymer films, i.e., conductive films consisting of poly(ethylene glycol) or Li+ montmorillonite can be obtained through a water-based process.

Ion Lithography of Single Ions Irradiation for Spatially Regular Arrays of Pores in Membranes of Polyethylene Terephthalate.

Routinely, in membrane technology, the decay from radioactive particles or the bombardment of ions with MeV energy per nucleon have been employed for the production of narrow and long pores in membranes. Presently, the ion lithography is proposed to make the fabrication cost more affordable. It is prospective for the use of medium capacity accelerators making more feasible the fabrication of customized membranes. Thin polyethylene terephthalate foils have been patterned using 12 MeV O5+ ions and then processed to obtain good aspect ratio ion track pores in membranes. Pores of micrometric diameter with the following profiles were fabricated in the membranes: truncated cone, double conical, ideal cone, and cylindrical. Monitoring of the shape and size of pores has been attempted with a combination of Scanning Transmission Ion Microscope and a newly designed simulation program. This study is focused on the use of low-energy ions, accomplished in all laboratories, for the fabrication of membranes where the pores are not randomly traced and exhibit higher surface density and negligible overlapping than in membranes commonly manufactured. The good reproducibility and the ordered pore locations can be potentially utilized in applications such as microfluidics and organ-on-chip microsystems, where cells growing over porous substrates are used in simulation of biological barriers and transport processes.

Prevalence of Age-Related Macular Degeneration in the US in 2019

Age-related macular degeneration (AMD) is a leading cause of vision loss and blindness. AMD prevalence has not been estimated for the US in over a decade and early-stage AMD prevalence estimates are scarce and inconsistently measured. To produce estimates of early- and late-stage AMD prevalence overall and by age, gender, race and ethnicity, county, and state. The study team conducted a bayesian meta-regression analysis of relevant data sources containing information on the prevalence of AMD among different population groups in the US. We included data from the American Community Survey (2019), the National Health and Nutrition Examination Survey (2005-2008), US Centers for Medicare & Medicaid Services claims for fee-for-service beneficiaries (2018), and population-based studies (2004-2016). We included all relevant data from the US Centers for Disease Control and Prevention's Vision and Eye Health Surveillance System. The prevalence of early- and late-stage AMD was estimated and stratified when possible by factors including county, age group, gender, and race and ethnicity. Data analysis occurred from June 2021 to April 2022. The prevalence of early- (defined as retinal pigment epithelium abnormalities or the presence of drusen 125 or more microns in diameter in either eye) and late-stage (defined as choroidal neovascularization and/or geographic atrophy in either eye) manifestations of AMD. This study used data from nationally representative and local population-based studies that represent the populations in which they were conducted. For 2019, we estimated that there were 18.34 million people 40 years and older (95% uncertainty interval [UI], 15.30-22.03) living with early-stage AMD, corresponding to a crude prevalence rate of 11.64% (95% UI, 9.71-13.98). We estimated there were 1.49 million people 40 years and older (95% UI, 0.97-2.15) living with late-stage AMD, corresponding to a crude prevalence rate of 0.94% (95% UI, 0.62-1.36). Prevalence rates of early- and late-stage AMD varied by demographic characteristics and geography. We estimated a higher prevalence of early-stage AMD and a similar prevalence of late-stage AMD as compared with earlier studies. State-level and county-level AMD estimates may help guide public health practice.

A CONCISE LITERATURE REVIEW ON STUDY OF MICROSPONGES FROM ANCIENT TO RECENT

Polymeric microspheres enclosing an extremely porous surface are termed as microsponges. Microsponges are drug loaded microporous beads having 10-25 micron diameter. These may augment stability, ease side effects and amend drug release. Microsponge systems have capability to capture ample drug substances and are then formulated into various products like gel, cream, liquid or powder. Several research studies corroborated that microsponge entities possess non-irritant, non-mutant, non-allergic and non-toxicity features. Suitable analytical techniques for characterization of microsponges can be illustrated for suitable characteristic properties such as thickness, particle size and its distribution, surface and pore properties. Many problems such as repulsive odor, greasiness and skin exasperation are resolved by MDDS (microsponge drug delivery system). MDDS generates prolonged release and site specific action. In this review article, a concise outline of MDDS covering the principle, methods of formulation and characterization have been discussed. Microsponge delivery system (MDS) is primarily utilized for topical and oral formulations but it is also being explored for cosmetic formulations.

Natural Hollow Fiber-Derived Carbon Microtube with Broadband Microwave Attenuation Capacity.

Constructing hierarchical structures is indispensable to tuning the electromagnetic properties of carbon-based materials. Here, carbon microtubes with nanometer wall thickness and micrometer diameter were fabricated by a feasible approach with economical and sustainable kapok fiber. The carbonized kapok fiber (CKF) exhibits microscale pores from the inherent porous templates as well as pyrolysis-induced nanopores inside the wall, affording the hierarchical carbon microtube with excellent microwave absorbing performance over broad frequency. Particularly, CKF-650 exhibits an optimized reflection loss (RL) of -62.46 dB (10.32 GHz, 2.2 mm), while CKF-600 demonstrates an effective absorption bandwidth (RL &lt; -10 dB) of 6.80 GHz (11.20-18.00 GHz, 2.8 mm). Moreover, more than 90% of the incident electromagnetic wave ranging from 2.88 GHz to 18.00 GHz can be dissipated by simply controlling the carbonization temperature of KF and/or the thickness of the carbon-microtube-based absorber. These encouraging findings provide a facile alternative route to fabricate microwave absorbers with broadband attenuation capacity by utilizing sustainable biomass.

Erosion of Fuzz Layers Formed in Steady-State Plasma Discharge

The erosion of nanostructured tungsten and titanium by high-heat plasma flux, laser, and arcing is investigated. To fabricate nanostructural fuzz layers and hierarchical granularity on the surfaces, samples were exposed to helium plasma in the steady-state plasma device PLM-M, which is a linear plasma trap of an eight-pole multicusp magnetic field with parameters similar to the scrape-off layer and divertor plasma in a tokamak. Arcing ignited with a Nd:YAG laser pulse on the target fuzzy surface in the helium plasma resulted in the melting of fibers and the creation of craters of several microns in depth and several tens of microns in diameter.

Low frequency photoacoustic optical absorption measurement of aerosols

Atmospheric optical absorption, including the contribution from aerosols, is important in modeling optical propagation and for climate research. An open-celled photoacoustic aerosol sensing system was developed to operate at 150 Hz for measurement of absorption aerosols up to 3 microns in diameter with the design goal to achieve a sensitivity adequate to measure an absorption corresponding to a 1/e optical absorption length of 1 Mm. The advantage of a photoacoustic system is that it measures optical absorption only and is not sensitive to optical extinction due to scattering at low absorption levels. The system was calibrated against an existing black carbon absorption measurement unit made by Droplet Measurement Technologies, which operates at a shorter optical wavelength and higher acoustic frequency. With previous work focusing on measuring optical absorption by black carbon aerosols [J.A. Case and R.W. Smith,182nd meeting of the Acoustical Society of America in Denver, CO (5aPA)], this work covers measuring absorption by wet salt solutions of similar salt concentration to that oceanic aerosols. Experiments with the current system showed an anomalous photoacoustic signal appearing in the absence of any aerosols. Several solutions to eliminating the unwanted signal from the desired measurement are proposed and tested.

Microfluidics chip inspired by fish gills for blood cells and serum separation

In this paper, a microfluidic chip inspired by fish gills has been designed and fabricated in order to separate blood cells from serum. This microchip is modeled after fish gills which filter particles from fluids. In this way, the blood passes through a reservoir that contains several parallel rows of filter columns, which perform the filtering action. COMSOL Multiphysics software was used to conduct several simulations to optimize the pressure and velocity parameters of blood entering the microchip, and these parameters were used to determine the appropriate dimensions of the microchip. The simulation results indicate that the microchip is able to completely separate the cells from the serum, assuming a blood flow rate of 134 μl/s. With the help of the proposed filter, blood cells are separated from the plasma after 20 s and the aggregation occurs in the outlet reservoirs. In order to fabricate the microchip, the filter component made of polydimethylsiloxane (PDMS) was bonded to the copper substrate. In this paper a new copper to PDMS bonding process is proposed. Copper was chosen as the substrate because it allows the application of voltage to separate particles through the Dielectrophoresis method. The chemical etching method reinforced with noble metals was used to create micro holes on the silicon wafer, which are used to mold PDMS filters with a diameter of several micrometers. The main reservoir with a depth of 20 µm was created by the wet etching method. The reservoir was coated with silane coating and the oxygen plasma was utilized to bond the PDMS filters and the main reservoir. The copper substrate allows the microchip to be used with other electronic devices and circuits on printed circuit boards. Scanning Electron Microscopy (SEM) was used to observe the silane-coated copper surface, the micro holes on the silicon wafer, and the PDMS pillars. The topography and roughness of the copper surface before and after silane coating was evaluated through Atomic Force Microscopy (AFM). Optical Microscopy (OM) was utilized to observe the separation of the cells from the plasma. The results showed acceptable adhesion between copper and PDMS and good results for serum separation from blood cells.