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Volatile organic compounds are species of concern for indoor air quality. They are emitted from a wide range of indoor sources and in particular from construction materials. Industrialized wood-based panels made from various types of wood bonded with thermosetting adhesive resins have been shown to emit volatile organic compounds over months or even years mostly due to the petrochemical binders. Some studies have been conducted on binderless panels, but they mainly focused on the pressing parameters to be applied to optimize the panel characteristics. The aim of this research is to document the emissions from binderless panels and to access the volatile composition of wood processing through the molding of materials. For this purpose, binderless boards were manufactured from hardwoods, known to emit less than softwoods with different thermopressing temperatures and times. Emissions were studied by placing the materials in microchambers. Volatile organic compounds were then sampled and analyzed by various chromatographic methods. On the other hand, materials were pyrolyzed and then analyzed by gas chromatography and mass spectrometry. The implemented protocols proved suitable for the determination of more than 40 organic compounds, among which are aldehydes, aromatics, furans and derivatives, and carboxylic acids. [ABSTRACT FROM AUTHOR]

Abstract The use of engineered scaffolds or stem cells is investigated widely in the repair of injured musculoskeletal tissue. However, the combined regeneration of hierarchical osteochondral tissue remains a challenge due to delamination between cartilage and subchondral bone or difficulty in spatial control over differentiation of transplanted stem cells. Here, two types of composite spheroids are prepared using adipose‐derived stem cells (hADSCs) and nanofibers coated with either transforming growth factor‐β3 or bone morphogenetic growth factor‐2 for chondrogenesis or osteogenesis, respectively. Each type of spheroid is then cultured within a 3D‐printed microchamber in a spatially arranged manner to recapitulate the bilayer structure of osteochondral tissue. The presence of inductive factors regionally modulates in vitro chondrogenic or osteogenic differentiation of hADSCs within the biphasic construct without dedifferentiation. Furthermore, hADSCs from each spheroid proliferate and sprout and successfully connect the two layers mimicking the osteochondral interface without apertures. In vivo transplantation of the biphasic construct onto a femoral trochlear groove defect in rabbit knee joint results in 21.2 ± 2.8% subchondral bone volume/total volume and a cartilage score of 25.0 ± 3.7. The present approach can be an effective therapeutic platform to engineer complex tissue.

The use of engineered scaffolds or stem cells is investigated widely in the repair of injured musculoskeletal tissue. However, the combined regeneration of hierarchical osteochondral tissue remains a challenge due to delamination between cartilage and subchondral bone or difficulty in spatial control over differentiation of transplanted stem cells. Here, two types of composite spheroids are prepared using adipose‐derived stem cells (hADSCs) and nanofibers coated with either transforming growth factor‐β3 or bone morphogenetic growth factor‐2 for chondrogenesis or osteogenesis, respectively. Each type of spheroid is then cultured within a 3D‐printed microchamber in a spatially arranged manner to recapitulate the bilayer structure of osteochondral tissue. The presence of inductive factors regionally modulates in vitro chondrogenic or osteogenic differentiation of hADSCs within the biphasic construct without dedifferentiation. Furthermore, hADSCs from each spheroid proliferate and sprout and successfully connect the two layers mimicking the osteochondral interface without apertures. In vivo transplantation of the biphasic construct onto a femoral trochlear groove defect in rabbit knee joint results in 21.2 ± 2.8% subchondral bone volume/total volume and a cartilage score of 25.0 ± 3.7. The present approach can be an effective therapeutic platform to engineer complex tissue. [ABSTRACT FROM AUTHOR]

To investigate the effects of microparticles on the immune system, a device was designed for an optimal culture environment. Macrophages phagocytose microparticles and produce inflammatory cytokines. In a culture environment in which macrophages phagocytose microparticles mixed in a culture medium, it remains unclear whether the macrophages can physically access all the microparticles present in the culture medium. In the culturing of fine particles, such as microparticles, it is necessary to devise methods that can realize a close biological contact between the macrophages and the microparticles. To enable macrophages to appropriately phagocytose microparticles, a microchamber with a glenoid hole for cell culturing was designed and manufactured. To clarify the effects of the size, administration amount, and administration time of the microparticles on the production of inflammatory cytokines, a system that can continuously deliver and collect the culture medium was introduced. The results obtained using these systems helped clarify the aforementioned effects. Our study confirms the possibility of employing a system that can optimally adjust the biological contact between macrophages and microparticles in a culture environment.

Digital assays, which have evolved from single-molecule detection technology, are attracting attention as a new method of measuring individual cells, proteins, and nucleic acids. The digital assays are characterized by their ability to directly measure individual molecules, enabling us to perform absolute quantification without the need for calibration curves and to determine the heterogeneity of a population. We first developed a digital assay for enzymes and applied the principle to digital ELISA and digital influenza assays. We demonstrate that the digital assays for enzymes are not only a new enzymology tools, but also have a wide range of applications such as elucidating the nature of viral populations. We will discuss how these new analytical techniques are opening up uncharted territory. [ABSTRACT FROM AUTHOR]

Artificial lipid bilayers structurally mimic cell membrane. Such the artificial lipid bilayers have been used for analyzing membrane transport by incorporating transporters in the artificial lipid bilayers. The membrane transport analysis using the artificial lipid bilayer is advantageous in the sense that less amount of off-target molecules exists in the system compared with the method using the actual cell membrane. That feature makes the measurement highly sensitive and reliable. In this report, the author introduces one of the methods to analyze membrane transport using the artificial lipid bilayers, focusing on fluorescent measurement of membrane transport using artificial lipid bilayer microchambers. [ABSTRACT FROM AUTHOR]

Source characteristics and health risks of indoor organophosphate esters (OPEs) are limited by the lack of knowledge on emission processes. This study attempted to integrate the contents and emissions of OPEs from indoor building materials to assess human health effects. Thirteen OPEs were investigated in 80 pieces of six categories of building materials. OPEs are ubiquitous in the building materials and ∑ 13 OPE contents varied significantly ( p < 0.05) from 72.8 ng/g (seam agent) to 109,900 ng/g (wallpaper). Emission characteristics of OPEs from the building materials were examined based on a microchamber method. Depending on the sample category, the observed initial area-specific emission rates of ∑ 13 OPEs varied from 154 ng/m 2 /h (carpet) to 2760 ng/m 2 /h (wooden floorboard). Moreover, the emission rate model was developed to predict the release levels of individual OPEs, quantify source contributions, and assess associated exposure risks. Source apportionments of indoor OPEs exhibited heterogeneities in multiple environmental media. The joint OPE contribution of wallpaper and wooden floorboard to indoor dust was up to 94.8%, while latex paint and wooden floorboard were the main OPE contributors to indoor air (54.2%) and surface (76.1%), respectively. Risk assessment showed that the carcinogenic risks of tris(2-chloroethyl) phosphate (3.35 × 10 -7 ) were close to the acceptable level (1 × 10 -6 ) and deserved special attention.

Abstract: This paper describes three‐dimensional (3D) tissue shape control of mouse neural stem cell (mNSC) micro tissues by using closed agarose microchambers for effective differentiation induction of neurons in vitro. Our agarose microchambers, made by micromolding, can be sealed with an agarose sheet to form the mNSC tissues along the shape of microchambers. We constructed lane‐shaped mNSC tissues with different width (∼60–210 μm) and thickness (∼25–95 μm) dimensions and induced differentiation to neurons with differentiation medium. We found that in thick tissues (thickness: >60 μm), distribution of differentiated neurons was not uniform, whereas in thin tissues (thickness: ∼30 μm), differentiated neurons were uniformly distributed with high differentiation efficiency. Our system to construct in vitro 3D neural tissues having uniformly distributed neurons at high differentiation ratio, could become an effective tool for drug screening using 3D neural tissues and 3D mNSC tissues under differentiation induction. [ABSTRACT FROM AUTHOR]

We investigate a motion of diatom cells stimulated by a halogen lamp irradiation. Diatom cells are single-celled organisms which have chloroplast. Chloroplast contains photosynthetic pigment which absorbs blue light (wave length of the light is 400 nm–450 nm) and red one (650 nm–700 nm). Light intensity of the halogen lamp is fixed about 500 Lx during the experiment. We used colored films to cut the blue or red light and observed motion of diatom cells by using the optical microscope. We found that the speed of diatom cells decreases when the colored film is inserted, and it increases after ejecting the film. It is noted that the light intensity is constant during the experiment, which means that we change wave length of the irradiated light. Our results show that the average speed of diatom cells is influenced by not the light intensity but the wave length of the light. [ABSTRACT FROM AUTHOR]

Background: Musculoskeletal foot disorders have a high incidence among overweight and obese individuals. One of the important factors causing this high incidence may be plantar fascia and heel pad (HP)-related mechanical changes occurring in these individuals. The aim of the present study was to investigate the plantar fascia and HP stiffness and thickness parameters in overweight and obese individuals and compare these values with those of normal-weight individuals. Methods: This study was carried out in 87 (52 female, 35 male) healthy sedentary individuals between the ages of 19 and 58 years (34 ± 11 years). Participants were subsequently categorized according to body mass index (BMI) as normal weight (18.5 kg/m² < BMI < 25 kg/m²) or overweight and obese (BMI ≥25 kg/m²). Plantar fascia and HP thickness and stiffness were measured with an ultrasonography device using a linear ultrasonography probe. Results: Overweight and obese individuals had higher HP thickness (P < .001), plantar fascia thickness (P = .001), heel pad microchamber layer (MIC) stiffness (P < .001), and heel pad macrochamber layer (MAC) stiffness (P < .001), whereas they had lower plantar fascia stiffness (P < .001) compared with the individuals with normal weight. BMI had a moderate correlation with HP thickness (P < .001, r = 0.500), plantar fascia thickness (P = .001, r = 0.536), MIC stiffness (P < .001, r = 0.496), and MAC stiffness (P < .001, r = 0.425). A negative and moderate correlation was found between BMI and plantar fascia stiffness (P < .001, r = -0.439). Conclusion: Increased BMI causes a decrease in the stiffness of plantar fascia and an increase in the thickness of the plantar fascia as well as the thickness and stiffness of HP. Increased body mass could cause changes in the mechanical properties of HP and plantar fascia. [ABSTRACT FROM AUTHOR]

Detailed information about the biomechanical behaviour of plantar heel pad tissue contributes to our understanding of load transfer when the foot impacts the ground. The objective of this work was to obtain the hyperelastic and viscoelastic material properties of heel pad sub-layers (skin, micro-chamber and macro-chamber layers) in-vivo . An anatomically detailed 3D Finite Element model of the human heel was used to derive the sub-layer material properties. A combined ultrasound imaging and motorised platform system was used to compress heel pad and to create input data for the Finite Element model. The force–strain responses of the heel pad and its sub-layers under slow compression (5 mm/s) and rapid loading-hold-unloading cycles (225 mm/s), were measured and hyperelastic and viscoelastic properties of the three heel pad sub-layers were estimated by the model. The loaded (under ∼315 N) thickness of the heel pad was measured from MR images and used for hyperelastic model validation. The capability of the model to predict peak plantar pressure was used for further validation. Experimental responses of the heel pad under different dynamic loading scenarios (loading-hold-unloading cycles at 141 mm/s and sinusoidal loading with maximum velocity of 300 mm/s) were used to validate the viscoelastic model. Good agreement was achieved between the predicted and experimental results for both hyperelastic (<6.4% unloaded thickness, 4.4% maximum peak plantar pressure) and viscoelastic (Root Mean Square errors for loading and unloading periods <14.7%, 5.8% maximum force) simulations. This paper provides the first definition of material properties for heel pad sub-layers by using in-vivo experimental force–strain data and an anatomically detailed 3D Finite Element model of the heel. [ABSTRACT FROM AUTHOR]

We present a method to detect the transporter activity of intact adherent cells using a microchamber device. When adherent cells are seeded onto the poly-di-methyl siloxane (PDMS) substrate having microchambers with openings smaller than the size of a cell, the cells form a confluent layer that covers the microchambers, creating minute, confined spaces. As substances exported across the cell membrane accumulate, transporter activity can be detected by observing the fluorescence intensity increase in the microchamber. We tested the microchamber device with HeLa cells overexpressing MDR1, an ATP-binding cassette (ABC) transporter, and succeeded in detecting the transport of fluorescence-conjugated paclitaxel, the anti-cancer drug, at the single-cell level.

We have recently presented an integrated silicon-glass opto-chemical sensor forlab-on-chip applications, based on porous silicon and anodic bonding technologies. In thiswork, we have optically characterized the sensor response on exposure to vapors of severalorganic compounds by means of reflectivity measurements. The interaction between theporous silicon, which acts as transducer layer, and the organic vapors fluxed into the glasssealed microchamber, is preserved by the fabrication process, resulting in optical pathincrease, due to the capillary condensation of the vapors into the pores. Using theBruggemann theory, we have calculated the filled pores volume for each substance. Thesensor dynamic has been described by time-resolved measurements: due to the analysischamber miniaturization, the response time is only of 2 s. All these results have beencompared with data acquired on the same PSi structure before the anodic bonding process.

As the number of available cell types grows, it becomes necessary to develop more effective ways to optimize the cell-culture medium for each cell line and culture condition. However, because of the vast number of parameters that must be decided, such as the combination of components, optimization is both laborious and costly. Microdevices are a cost-effective way to perform such evaluations because they use only a small volume of media and enable high-throughput analyses. However, assays performed in microdevices are themselves minimized, and each assay unit (well/chamber) commonly contains an insufficient number of cells for comprehensive evaluations such as gene-expression or flow-cytometry analyses. To address this issue, we introduced image-based analysis in conjunction with microdevice assays; this approach allows quantification of every cell in each assay unit. To quantitatively profile differences in cellular behaviors in a microdevice under different culture media conditions, we developed a non-staining image-based analysis method that utilizes cellular morphology. Our approach combines the structural advantages of microdevices, which can increase the stability of images, and the quantitative advantages of an image-based cell evaluation technique that utilizes time-course population change in several morphological features. Our results demonstrate that cellular changes due to small alterations in the concentration of serum in medium or differences in the basal medium can be profiled using only microscopic images. [ABSTRACT FROM AUTHOR]

The goal of the study was to evaluate the reliability of supersonic shear wave elastography in measuring heel pad stiffness and the change in heel pad stiffness in patients with plantar heel pain. In the reliability test involving 12 normal participants, each heel pad was tested six times in succession, and adequate reliability was reflected in the intraclass correlation coefficients (0.95, 0.93 and 0.96 for the microchambers, macrochambers and bulk heel pad, respectively). In the clinical assessment involving 20 normal participants and 16 unilateral plantar heel pain patients, diseased heel pads (86.8 ± 22.9, 36.8 ± 7.7 and 46.6 ± 10.9 kPa for the microchambers, macrochambers and bulk heel pad, respectively) were significantly stiffer than unaffected heel pads (66.8 ± 14.1, 25.2 ± 5.7, 34.2 ± 6.6 kPa) and those of normal participants (60.9 ± 11.4, 26.3 ± 6.1, 31.8 ± 6.3 kPa), suggesting that the heel pad with plantar heel pain was associated with loss of elasticity. [ABSTRACT FROM AUTHOR]

A numerical investigation is conducted to predict the thermal and hydraulic performances of the microchannel heat sink (MCHS) with different geometric parameters of triangular rib in the transverse microchamber. The parametric variables of width, length and height of the triangular rib are studied to find optimum design. The flow structure and characteristics of the interrupted MCHS are interpreted in details. The dimensionless ratios of average Nusselt number, friction factor and thermal enhancement factor are evaluated. It is found that the heat transfer rate is increasing with the increase of rib width and height, but decreasing with the increase of rib length. The boundary layer interruption and redevelopment effects introduced by the triangular rib are discussed. The results of thermal enhancement factor reveals an optimum geometrical parameters for the triangular rib with width = 100 μm, length = 400 μm and height = 120 μm for about Reynolds number of 500, yielding 43% enhancement relative to non-interrupted rectangular MCHS at equal pumping power. The results of mean Nusselt number ratio reveal an optimum enhancement of 56% relative to non-interrupted MCHS. [ABSTRACT FROM AUTHOR]

Number of a molecule is discrete by its nature. Therefore, when detection sensitivity of analytical methods approaches the single molecule level, one faces the intrinsic discreteness of the measured concentration and number of analytes. An emerging analytical method that employs this intrinsic discreteness is digital counting. When an analyte solution is partitioned into many small reaction compartments, such that each molecule is individually encapsulated into a compartment, the analyte quantification is inevitably digitized; each compartment contains none or one molecule of analyte. When a solution of enzyme or enzyme-conjugated molecule is partitioned into such small reactors with fluorogenic substrate, one can count the number of the molecule as that of fluorescent reactors under an optical microscope. We refer to this strategy as “digital counting”. One of the most successful examples of digital counting is digital ELISA, in which target molecules are individually encapsulated in a water-in-oil droplet after bound to enzyme-conjugated antibody. Although the chemistry of digital ELISA; antibody and enzyme is common to conventional ELISA, the detection sensitivity of digital ELISA is higher than that of conventional ELISA by 4 to 6 orders of magnitude. In this review, we introduce recent achievements in digital ELISA and relevant methods. [ABSTRACT FROM AUTHOR]

Pine wood particles were treated with effluents from the wood-board manufacturing industry or from a communal clarification plant, and the effect of these treatments on aldehyde emissions of wood material was tested. Pine wood strands were treated in the same manner and strand boards were produced from the treated material on a laboratory scale. The 28-day volatile organic compound emissions of the boards were determined in a microchamber using Tenax-TDAS/GC-MS analytics. Boards made from treated strands exhibited significantly lower aldehyde emissions compared to control boards. Analyses of microflora and of wood extractives confirmed that microbial metabolism in industrial effluents consumed unsaturated fatty acids (UFAs) present in wood. As UFAs are the source of aldehyde emissions due to auto-oxidation, the aldehyde emission was consequently reduced. A routine treatment of wood raw material with properly chosen industrial effluents may therefore be regarded as a cost-reducing and efficient method for the utilisation of industrial waste waters. [ABSTRACT FROM AUTHOR]

In this study, we used a microchamber to observe and analyze the gliding phenomenon of Navicula pavillardii diatom cells at different temperatures. The temperature of the culture medium was varied from 17.0 to 30.0 °C to examine the effect of temperature on diatom movement. Movement of each cell at different temperatures was monitored by use of an inverted optical microscope and continuously recorded as video data, from which the velocities of each cell were calculated, by using dedicated software to perform two-dimensional trajectory analysis. The velocities of the same cell at different temperatures were thereby successfully compared. The results showed that the change in cell velocity was insignificant when the temperature was increased from 17.0 to 25.0 °C. When the temperature was increased from 17.0 to 27.5 °C, non-uniformly disrupted cell movement was observed. When the temperature was further increased to 30.0 °C, cell movement was clearly inhibited. By use of single-cell analysis, the effects of the temperature increases on diatom movement were successfully evaluated. Finally, we characterized the experimental data by performing t tests to evaluate the effects of variations of the movement of individual cells on the data analysis. [ABSTRACT FROM AUTHOR]

Lab-on-a-Chip devices exploit micro/nanoengineering techniques to develop miniaturized systems for handling and manipulating small volumes of fluids. Here, we demonstrate a microfluidic device for culturing cells in closed microchambers that is designed to be compatible with standard biological procedures. This approach facilitates the thermal and gaseous equilibration of all the components, preventing the nucleation of air bubbles. Serial asymmetrical loadings were performed to realize co-cultures with initial topographical organization. The migration of two different cell types was monitored for 72 h by high-resolution fluorescence imaging. [ABSTRACT FROM AUTHOR]

Isolation of cells from heterogeneous biological samples is critical in both basic biological research and clinical diagnostics. Affinity‐based methods, such as those that recognise cells by binding antibodies to cell membrane biomarkers, can be used to achieve specific cell isolation. Microfluidic techniques have been employed to achieve more efficient and effective cell isolation. By employing aptamers as surface‐immobilised ligands, cells can be easily released and collected after specific capture. However, these methods still have limitations in cell release efficiency and spatial selectivity. This study presents an aptamer‐based microfluidic device that not only achieves specific affinity cell capture, but also enables spatially selective temperature‐mediated release and retrieval of cells without detectable damage. The specific cell capture is realised by using surface‐patterned aptamers in a microchamber on a temperature‐control chip. Spatially selective cell release is achieved by utilising a group of microheater and temperature sensor that restricts temperature changes, and therefore the disruption of cell–aptamer interactions, to a design‐specified region. Experimental results with CCRF‐CEM cells and sgc8c aptamers have demonstrated the specific cell capture and temperature‐mediated release of selected groups of cells with negligible disruption to their viability. [ABSTRACT FROM AUTHOR]

ABSTRACT A bacteria-based microrobot (bacteriobot) was proposed and investigated as a new type of active drug delivery system because of its useful advantages, such as active tumor targeting, bacteria-mediated tumor diagnosis, and therapy. In this study, we fabricated a bacteriobot with enhanced motility by selective attachment of flagellar bacteria ( Salmonella typhimurium). Through selective bovine serum albumin (BSA) pattering on hydrophobic polystyrene (PS) microbeads, many S. typhimurium could be selectively attached only on the unpatterned surface of PS microbead. For the evaluation of the chemotactic motility of the bacteriobot, we developed a microfluidic chamber which can generate a stable concentration gradient of bacterial chemotactic chemicals. Prior to the evaluation of the bacteriobot, we first evaluated the directional chemotactic motility of S. typhimurium using the proposed microfluidic chamber, which contained a bacterial chemo-attractant ( L-aspartic acid) and a chemo-repellent (NiSO4), respectively. Compared to density of the control group in the microfluidic chamber without any chemical gradient, S. typhimurium increased by about 16% in the L-aspartic acid gradient region and decreased by about 22% in the NiSO4 gradient region. Second, we evaluated the bacteriobot's directional motility by using this microfluidic chamber. The chemotactic directional motility of the bacteriobot increased by 14% and decreased by 13% in the concentration gradients of L-aspartic acid and NiSO4, respectively. These results confirm that the bacteriobot with selectively patterned S. typhimurium shows chemotaxis motility very similar to that of S. typhimurium. Moreover, the directional motilities of the bacteria and bacteriobot could be demonstrated quantitatively through the proposed microfluidic chamber. Biotechnol. Bioeng. 2014;111: 134-143. © 2013 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

In this work, a microfabricated anode based on gold coated poly(ϵ-caprolactone) fiber was developed that outperformed gold microelectrode by a factor of 2.65-fold and even carbon paper by 1.39-fold. This is a result of its ability to three-dimensionally interface with bacterial biofilm, the metabolic 'engines' of the microbial fuel cell (MFC). We also examined unavoidable issues as the MFC is significantly reduced in size (e.g. to the microscale); (1) bubble production or movement into the microchamber and (2) high sensitivity to flow rate variations. In fact, intentionally induced bubble generation in the anodic chamber reduced the MFC current density by 33% and the MFC required 4 days to recover its initial performance. Under different flow rates in the anode chamber, the current densities were almost constant, however, the current increased up to 38% with increasing flow rate in the cathode. [ABSTRACT FROM AUTHOR]

Techniques to separate cells are widely applied in immunology. The technique to separate a specific antigen on a microfluidic platform involves the use of a shear horizontal surface-acoustic-wave (SH-SAW) sensor. With specific antibodies conjugated onto the surface of the SH-SAW sensors, this technique can serve to identify specific cells in bodily fluids. Jurkat cells, used as a target in this work, provide a model of cells in small abundance (1:1000) for isolation and purification with the ultimate goal of targeting even more dilute cells. T cells were separated from a mixed-cell medium on a chip (Jurkat cells/K562 cells, 1/1000). A novel microchamber was developed to capture cells during the purification, which required a large biosample. Cell detection was demonstrated through the performance of genetic identification on the chip. [ABSTRACT FROM PUBLISHER]

Intracellular structures of biological cells can be disturbed by exposure to nanosecond pulsed electric field (nsPEF). A microchamber-based delivery system mounted on a microscope setup for real-time exposure to nsPEF is studied in this paper. A numerical and experimental characterization of the delivery system is performed both in frequency and time domains. The microchamber delivery system presents a high impedance compared to classical 50 Ω loads. Its frequency behavior and limits are investigated using an in-house finite-difference time-domain (FDTD) simulator and through experimental measurements. High-voltage measurements for two nsPEF generators are carried out. The applied pulse voltage measured across the microchamber electrodes is ∼1 kV, corresponding to ∼10 MV/m electric fields in the microchamber. Depending on the nsPEF generator used, the measured pulse durations are equal to 3.0 and 4.2 ns, respectively. The voltage distribution provided by FDTD simulations indicates a good level of homogeneity across the microchamber electrodes. Experimental results include permeabilization of biological cells exposed to 3.0-ns, 10-MV/m PEFs. [ABSTRACT FROM AUTHOR]

We describe the development, fabrication and testing of a microfluidic chamber for dielectrophoretic field-flow separation of biological cells based on their electrical properties. The chamber was constructed from a single Pyrex wafer with interdigitated Au electrodes, a spacer, and a top cover glass, making the events in the chamber observable under most optical microscopes. The dimensions were optimized based on numerical computations of the electric field, its gradient and the fluid-flow velocity profile. The electrodes were fabricated using photolithography. A double-sided self-adhesive tape of 100 \mu \m thickness was used as a spacer, with an opening of 80 mm length and 20 mm width cut in its middle to form a channel of 100 \mu \m height, and with water-resistant acrylic glue of the tape holding the glass plates together and providing a tight seal. The glue loses its adhesive properties above 70 ^\circ\C, allowing for easy disassembly of the chamber in hot water and its thorough cleaning. A 1:1 mixture of normal and 50 ^\circ\C-heat-treated CHO cells was used to test the chamber. A 93% efficiency of separation was obtained, confirming the usefulness of the chamber in separating cells with sufficient differences in electrical properties of their membranes. [ABSTRACT FROM PUBLISHER]

Emission test chambers or cells are used to determine organic vapour emissions from construction products under controlled conditions. Polymeric car trim component emissions are typically evaluated using direct thermal desorption/extraction. The Microchamber/Thermal Extractor (μ-CTE, Markes International) was developed to provide both a complementary tool for rapid screening of volatile organic compound (VOC) emissions—suitable for industrial quality control—and a means for thermal extraction of larger, more representative samples of car trim components. To determine the degree of correlation between conventional emission test methods and the microchamber, experiments were carried out under different conditions of temperature, air change rate and sample conditioning time. Good quantitative and qualitative correlation was obtained for measurements at ambient temperature. Moreover, it was shown that ambient-temperature emissions data collected using the μ-CTE as rapidly as possible—i.e. with minimal or no sample conditioning time—nevertheless provided a reliable guide as to how well that material would perform in subsequent 3-day chamber tests of VOC emissions. The parameters found to have the greatest influence on data correlation for experiments carried out at elevated temperatures were the sample mass (for bulk emissions testing) and the conditioning time. The results also showed that, within the constraints of inherent sample homogeneity, the μ-CTE gave reproducible emissions data, despite its small sample size/capacity relative to that of conventional chambers. Preliminary results of modelling the air flow within a microchamber using computational fluid dynamics showed a high degree of turbulent flow and two potential areas of still air which could cause sink effects. However, the experimental data reported here and in previous studies showed enhanced recovery of semivolatile components from the μ-CTE relative to a recovery from a 1 m3 conventional chamber. This indicates that if these areas of relatively still air are present within the microchamber, they do not appear to be significant in practice. [ABSTRACT FROM AUTHOR]

Abstract: The compatibility of porous silicon and anodic bonding technologies for the realization of sensing micro-components in lab-on-chip applications is demonstrated. In particular, we have developed and tested an innovative anodic bonding process: voltage, time and temperature have been properly matched in order not to affect the properties of the transducing material, which can be strongly modified by thermal treatments through oxidation. Two devices for chemical and biological sensing have been designed, fabricated and tested. The results obtained are very promising, especially regarding further integration of porous silicon and glass with optical and microelectromechanical instruments. [Copyright &y& Elsevier]

Nanosecond pulsed electric fields can pass through the external membrane of biological cells and disturb fast-responding intracellular structures and processes. To enable real-time imaging and investigation of these phenomena, a microchamber with integral electrodes and optical path for observing individual cells exposed to ultrashort electric pulses was designed and fabricated utilizing photolithographic and microelectronic methods. SU-8 photoresist was patterned to form straight sidewalls from 10 to 30 μm in height, with gold film deposited on the top and sidewalls for conductive, nonreactive electrodes and a uniform electric field. Channel dimensions (10-30 μm×100 μm×12000 μm) are suitable for observations of mammalian cells during nanosecond, megavolt-per-meter pulsed electric field exposure. Experimental studies utilizing the electrode microchamber include live-cell imaging of nanoelectropulse-induced intracellular calcium bursts and membrane phospholipid translocation. [ABSTRACT FROM PUBLISHER]

Abstract: A process for creating and testing an on-chip microscale vacuum chamber utilizing standard microfabrication techniques was developed. The fabrication of the microchamber is compatible with the processing of vertical field emission (FE) devices. Using 14 μm diameter patterned photoresist octagons as a mold, a rigid tungsten structure was deposited covering a 2 μm diameter etched hole representing the device region. Standard microfabrication techniques were employed to etch eight-1 μm diameter vias through the tungsten structural layer to allow for removal of the photoresist layer. Subsequent to the photoresist removal, an aluminum film was sputter deposited in vacuum to encapsulate the chamber in a sub-atmospheric pressure environment. Patterning of electrodes into the metallic layers allowed for subsequent testing of the microchamber. The results of current–voltage measurements that were performed on encapsulated and unencapsulated structures demonstrated the ability of the microchambers to maintain vacuum. The described fabrication process yielded a microchamber with a contained pressure of 50 mTorr, however, the process is also compatible with high-vacuum sealing. In this paper, we report the details of the fabrication process and provide the results of testing a vacuum-encapsulated microchamber. [Copyright &y& Elsevier]

We have developed a on-chip single-cell microcultivation assay as a means of observing the adaptation process of single bacterial cells during nutrient concentration changes. This assay enables the direct observation of single cells captured in microchambers made on thin glass slides and having semipermeable membrane lids, in which cells were kept isolated with optical tweezers. After changing a medium of 0.2% (w/v) glucose concentration to make it nutrient-free 0.9% NaCl medium, the growth of all cells inserted into the medium stopped within 20 min, irrespective of their cell cycles. When a nutrient-rich medium was restored, the cells started to grow again, even after the medium had remained nutrient-free for 42 h. The results indicate that the cell’s growth and division are directly related to their nutrient condition. The growth curve also indicates that the cells keep their memory of what their growth and division had been before they stopped growing. [Copyright &y& Elsevier]

This paper reports transportation of the target microbe by the laser trapped microtools with minimum laser irradiation to the target. The size of a microtool (MT) is around micrometer. The MTs are manipulated by the focused laser under the microscope to manipulate the target microbe. Here we propose a pinpoint injection method of MTs at the desired location in the microchamber, which is filled with liquid. At first, we classified the injection method of the MTs in four categories. Here we employed a new method to install the MTs inside the microchamber. We developed a MT holding chip to install the MTs. The MTs were injected in the microchamber, and were manipulated successfully by the laser scanning micromanipulator to transport the target microbe for separation. The proposed method is useful for the pinpoint injection of MTs and separation by the indirect micromanipulation. [ABSTRACT FROM PUBLISHER]

We have shown recently that isolated cochlear outer hair cells change their axial stiffness when their membrane potential is altered under voltage-clamp. Here we extend those observations, using a more stable mechanical platform, the microchamber, to hold the cells and to deliver voltage commands. Cell stiffness is determined by opto-electronically measuring the amplitude of motion of a flexible fiber as it is loaded by the cell. Cell stiffness is decreased by depolarization and increased by hyperpolarization. The stiffness changes have been measured with sinusoidal electrical command signals up to 1750 Hz and fiber motion up to 2000 Hz. It is shown that electrically evoked stiffness changes and length changes (electromotility) have very similar characteristics and may arise in a common process. [ABSTRACT FROM AUTHOR]

We propose a new technique for quantitative trajectory analysis of gliding phenomenon of Navicula pavillardii (NP) and Seminavis robusta (SR) diatom cells by single cell observation using a glass microchamber in this short technical note. Two-dimensional trajectory analysis of cell movements was used to determine the angular velocity, velocity, and migration distances of the diatom movement. Based on the trajectory analysis, we found that asymmetrically shaped SR had a larger angular velocity with large fluctuations compared to symmetrically shaped NP, although the velocity of SR was less than that of NP. It suggests that lateral frictional force in a culture medium is an important factor for diatom movements. Our results revealed that the single cell observation using a glass microchamber is effective on quantitative analysis of angular velocity of diatom gliding. [ABSTRACT FROM AUTHOR]

A new method was developed to study the migration of lymphocytes under in vitro conditions. Attractant fluid was added to the appropriate lower wells, which were filled to the brim. Peripheral blood mononuclear cells were labelled withCr and then put into the upper wells. Surface tension and capillary force are enough to make clamping of these plates possible, separated by a polycarbonate filter, 15 μm thick with a pore size of 8 μm, between these two standard multiwell microculture plates. After three hours of incubation at +37°C in a humidified 5% CO atmosphere, the migrated cells were harvested from the lower wells using a semiautomatic harvester, and the radioactivity was counted. The present method makes it unnecessary to enrich or select for different cell subsets for migration studies. Instead, density gradient separated mononuclear cells as such can be used to assess their migratory capacity. [ABSTRACT FROM AUTHOR]

[Display omitted] • Visualization of asphaltene precipitation induced by diffusive mixing in-situ. • Primary particles (r ~ 300 nm) are the basic units from asphaltene precipitation. • Asphaltene precipitation in a quasi-2D chamber is quicker at higher concentration of paraffinic solvent. Paraffinic froth treatment (PFT) is an essential step in oilsands extraction. The ability to quantitatively understand and control asphaltene precipitation induced by solvent dilution is key to technology innovation in PFT process. In this work, we investigate the early stage of asphaltene precipitation in a model oil system in response to diffusive solvent addition in quasi-2D confinement. Using total internal reflection fluorescence microscope, we provide direct visualization of the size distribution and structural characteristics of asphaltene precipitates with a spatial resolution of ~ 200 nm and temporal resolution of 250 ms. Our results show the correlation between the size and number of the asphaltene particles and the concentration of the paraffinic solvent in the diluent. Notably the aggregates were found to consist of primary submicron particles with a similar size from 200 nm to 400 nm in radius. These particles may be the primary elementary units that aggregate and form bigger particles via aggregation. The growth time of asphaltene particles decreases with increase n-pentane concentration in the observation area. The findings from this work provide new insight into the effects of solvent mixing on the size distribution and morphological characteristics of asphaltene precipitates that are important for association with water and solids and separation properties. [ABSTRACT FROM AUTHOR]

Magnetic nanoparticles have attracted significant attention in various disciplines, including engineering and medicine. Microfluidic chips and lab-on-a-chip devices, with precise control over small volumes of fluids and tiny particles, are appropriate tools for the synthesis, manipulation, and evaluation of nanoparticles. Moreover, the controllability and automation offered by the microfluidic chips in combination with the unique capabilities of the magnetic nanoparticles and their ability to be remotely controlled and detected, have recently provided tremendous advances in biotechnology. In particular, microfluidic chips with magnetic nanoparticles serve as sensitive, high throughput, and portable devices for contactless detecting and manipulating DNAs, RNAs, living cells, and viruses. In this work, we review recent fundamental advances in the field with a focus on biomedical applications. First, we study novel microfluidic-based methods in synthesizing magnetic nanoparticles as well as microparticles encapsulating them. We review both continues-flow and droplet-based microreactors, including the ones based on the cross-flow, co-flow, and flow-focusing methods. Then, we investigate the microfluidic-based methods for manipulating tiny magnetic particles. These manipulation techniques include the ones based on external magnets, embedded micro-coils, and magnetic thin films. Finally, we review techniques invented for the detection and magnetic measurement of magnetic nanoparticles and magnetically labeled bioparticles. We include the advances in anisotropic magnetoresistive, giant magnetoresistive, tunneling magnetoresistive, and magnetorelaxometry sensors. Overall, this review covers a wide range of the field uniquely and provides essential information for designing "lab-on-a-chip" systems for synthesizing magnetic nanoparticles, labeling bioparticles with them, and sorting and detecting them on a single chip. [ABSTRACT FROM AUTHOR]

Formaldehyde is considered as carcinogenic and is emitted from particleboards and plywood used in toy manufacturing. Currently, the flask method is frequently used in Europe for market surveillance purposes to assess formaldehyde release from toys, but its concordance to levels measured in emission test chambers is poor. Surveillance laboratories are unable to afford laborious and expensive emission chamber testing to comply with a new amendment of the European Toy Directive; they need an alternative method that can provide reliable results. Therefore, the application of miniaturised emission test chambers was tested. Comparisons between a 1 m3 emission test chamber and 44 mL microchambers with two particleboards over 28 days and between a 24 L desiccator chamber and the microchambers with three puzzle samples over 10 days resulted in a correlation coefficient r2 of 0.834 for formaldehyde at steady state. The correlation between the results obtained in microchambers vs. flask showed a high variability over 10 samples (r2: 0.145), thereby demonstrating the error-proneness of the flask method in comparison to methods carried out under ambient parameters. An exposure assessment was also performed for three toy puzzles: indoor formaldehyde concentrations caused by puzzles were not negligible (up to 8 µg/m3), especially when more conservative exposure scenarios were considered. [ABSTRACT FROM AUTHOR]

To demonstrate the practical use of a novel high-throughput screening system by a single cell reaction for the rapid screening of combinatorially mutated β-glucosidase 1 from Aspergillus oryzae, a yeast cell chip microchamber array in combination with yeast cell surface engineering was successfully developed. [Copyright &y& Elsevier]

We have developed a compact bead-alignment device with a bead-sized microchamber on a rotating cylinder. The cylinder fits inside a tube with bead-stock pipes containing different probe-conjugated beads and holes for bead-alignment capillaries. The cylinder rotates in the tube, and the microchamber transfers a single 100-μm-diameter bead from a pipe to one of the capillaries in 10 s. By using this process repeatedly, ‘bead arrays’, which are miniaturized DNA probe arrays in capillaries, were successfully fabricated. [Copyright &y& Elsevier]

The study of the sinking phenomenon of diatom cells, which have a slightly larger specific gravity (~1.3) compared to that of water, is an important research topic for understanding photosynthetic efficiency. In this study, we successfully demonstrated the observation of the sinking behaviors of four different species of diatom using a homemade “tumbled” optical microscope. A homemade 1 mm3 microchamber was employed to decrease the effects of convection currents. In the microchamber, diatom cells were basically settled in a linear manner without floating, although some of the cells were rotated during their sinking. Sinking speeds of the four species of diatom cells, Nitzschia sp., Pheodactylum tricornutum, Navicula sp., and Odontella aurita, were 0.81 ± 5.56, 3.03 ± 10.17, 3.29 ± 7.39, and 11.22 ± 21.42 μm/s, respectively, based on the automatic tracking analysis of the centroids of each cell. Manual analysis of a vector between two longitudinal ends of the cells (two-point analysis) was effective for quantitatively characterizing the rotation phenomenon; therefore, angles and angular velocities of rotating cells were well determined as a function of time. The effects of the cell shapes on sinking velocity could be explained by simulation analysis using the modified Stokes’ law proposed by Miklasz et al.

Diatoms are one of the major photosynthetic planktons. Here, we studied movements of aqueous suspensions of diatoms using a home-made 'tumbled' optical microscope system. The usual inverted optical microscope was reoriented using a homemade microscope stand so that the vertical sample stage contacted the surface. To observe the intrinsic sinking phenomenon of individual Navicula sp. cells, which have slender bodies, a homemade microchamber (1 mm3) was employed. Most of the cells uniformly sunk with a velocity of 2 to 14 μm/s. Automatic and manual two points trajectory analyses were carried out. The manual analysis was able to assess the rotation of cells. The novel methods provide new information about cell movements in aqueous systems that could not be obtained using conventional methods. Unlabelled Image • We observed sinking of diatom cells a home-made 'tumbled' optical microscope. • Automatic centroid mode analysis well revealed trajectories of hundreds of cells. • Manual two points analysis was effective on analyzing rotation of individual cells in water. [ABSTRACT FROM AUTHOR]