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The neural representation of the body is easily altered by integrating multiple sensory signals in the brain. The “rubber hand illusion” (RHI) is one of the most popular experimental paradigms to investigate this phenomenon. During this illusion, ownership of a rubber hand is created. It was shown that external and continuous cooling of the palm enhanced the RHI, suggesting an association between disrupting the autonomic nervous system regulation and disrupting the sense of ownership of a specific limb. However, the effects of artificially cooling the entire hand for a short period on the magnitude of the illusion remain unknown. Here we show that cooling the hand by immersing it in water for 1 min enhanced the RHI strength. We found that cooling the entire hand enhanced the proprioceptive drift during the RHI but not the subjective feeling of ownership. In contrast, warming and intense cooling of the entire hand did not affect the RHI strength. Our results suggest that transient and moderate cooling of the entire hand was sufficient in enhancing the illusory disembodiment of one’s own hand.

This study develops a technique to control the timing, spacing (interval), and velocity of particles in a microchannel flow by periodically exerting forces on the particles over space and time. The periodic force was produced by dielectrophoretic force using boxcar-shaped electrodes on the channel wall. We could define the timing, interval, and velocity of the particles by configuring the on–off cycles of the applied voltage. Controlling the particle spacing and timing when it crosses a position in the channel and the focusing effect in the cross-sectional position could improve the performance and throughput of microfluidics, particularly for sensing, active sorting, and encapsulation of particles and cells. The proposed technique was first evaluated by a one-dimensional analysis based on a perturbation theory. We conducted a numerical simulation to solve the dielectrophoretic force distribution and the equation of motion of the particles to understand the relationship between the force and the particle motion in the boxcar-electrode region. We measured the velocity and position of the micro-particles flowing over the boxcar-electrode region in the microchannel and demonstrated the performance and accuracy of the proposed technique for alignment and timing control. The probability density functions (PDFs) of the period between the particles, particle velocity, and timing, concentrated at the target value with minimal variation. Furthermore, the measurement of particles with diameters of 8, 10, and 12 μm resulted in the same PDFs, which showed the applicability to a reasonable variation of particle diameters.

Heat transfer enhancement in the low Reynolds number condition is increasingly required with the perpetual attempt to integrate and miniaturize electronic devices. The authors have suggested the application of photo-rheological fluid, whose rheological properties change by external photic stimulus, to a coolant of small heat exchangers. High heat transfer state and low pressured drop state can be switched by light irradiation to the fluid according to the demand for heat transfer enhancement. This study investigated how the change of viscoelasticity of photosensitive micellar solutions by light irradiation relates to flow structure and heat transfer performance. Flow visualization and heat transfer measurement were conducted using an aqueous solution of surfactant and counterions (cetyl-trimethyl-ammonium bromide/sodium salicylate/ortho-methoxy cinnamic acid) with different light irradiation time in serpentine channels. The results showed that the decrease of the viscoelasticity with light irradiation caused the decrease in heat transfer rate and pressure drop. In the flow visualization, two types of secondary vortex, i.e., a single large-scaled vortex and a pair of counter-rotating vortices, were observed. As the light irradiation time increased, flow unsteadiness diminished, and the frequency in the appearance of a single vortex and fast flow near wall decreased. The decrease in heat transfer rate and pressure drop with light irradiation was ascribed to the deterioration of fluid mixing by flow unsteadiness, the reduction of momentum and thermal diffusion by the decrease in near-wall velocity gradient, and the decrease in the strength of a pair of vortices.

Wavelength dispersion is a universal phenomenon in refractive optics that degrades optical performances. Current mitigation methods are being greatly challenged by the demanding requirements of miniaturization, low aberrations, high throughput, and accurate manufacture. Here, we propose an unconventional monolithic honeycomb-like lens concept with topological degrees of design freedom, capable of near diffraction-limited achromatic performance. To automate the design process, a methodological framework is presented that directly evolves the honeycomb lens from a flat window, instead of a knowledge-based starting geometry. The honeycomb lens performance at the full field of view is remarkably better than either traditional aspheric lenses or commercial cascaded lenses. It also overcomes limitations of flat metalenses, which have extremely small aperture sizes and suffer from multi-order aberrations. This topological honeycomb lens concept may pave the way to inexpensive and compact achromatic optics for focusing and imaging applications in consumer cameras, wearable optics, virtual reality, etc.

A novel optical method that can measure fluid temperature at the microscopic scale by measuring fluorescence polarization is described in this paper. The measurement is much less influenced by fluorescence quenching effects, which is a significant issue in conventional laser-induced fluorescence methods. Therefore, the effects of the other properties of the fluid can be reduced considerably in the proposed method, thus has the potential of leading to greater reliability in measuring the temperature. An experiment was performed in a microchannel flow by using fluorescent molecule probes. The relationship between the fluid temperature and the measured fluorescence polarization degree is evaluated to derive the correlation curve. In addition, the effects of the fluid viscosity and fluid pH on the fluorescence polarization degree are discussed to evaluate the influence of the quenching effects. The results showed that the fluorescence polarization is considerably less sensitive to the quenching factors as compared with the fluorescence intensity measurements. Furthermore, a strong linear correlation between the polarization degree and the fluid temperature was obtained. This relationship agreed well with the theoretical one qualitatively and confirmed the validity of the measurements and feasibility of the proposed method.

The motion and concentration distribution of particles and cells in flow are important factors which affect the fluid properties, flow structure, and mass transfer of biological and chemical species in blood vessels and channels. In this study, number density distributions of particles and rigidized red blood cells (RBCs) in a microchannel whose size is comparable to the sizes of the particle and RBCs are measured. Measurements were conducted at several streamwise locations for suspensions of particles and RBCs with hematocrits of the order of 10% and particle sizes of 5 and 8 µm. Analysis of the migration and resulting concentration distribution of the particles and RBCs was conducted using a model that considers the particle–particle collision and fluid dynamic force. As the size of the microchannel is small, the wall effect on the collision and migration of the particles and RBCs was significant. The wall reduced the overlapping area of the particles in collision and their displacement after collision (mobility), which varied the number, location, and magnitude of the maximum peaks observed in the number density distribution. Furthermore, the rotational motion of the rigidized RBCs in the channel flow reduced the effective lengths of the overlapping area and displacement, whereas it produced additional migration at the wall. With these terms added in the model, the number density distributions of the particles and RBCs showed reasonable agreement with those of the measurement. Especially, the number of peaks and their location for the maximum values in the model and measurement matched well.

A continuum model for the transport of red blood cells (RBC) inside arteries and capillaries of small diameters is proposed. The pressure and velocity fields are solved using the Navier-Stokes equations while the distribution of the RBC volume fraction, namely, hematocrit is obtained by solving the particle transport equation arising from the diffusive flux model. The momentum and hematocrit transport equations are coupled through a hematocrit-dependent blood viscosity model. The coupled equations are numerically solved using a 3D unstructured finite volume method. The proposed model predicts the shear induced diffusion of RBCs where RBCs migrate from the wall to the center of the blood vessel leading to a cell free layer (CFL) near the wall. Three geometries with sizes of the order of 40 µm have been considered for the present work. For flow inside a tube, results in terms of the concentration distribution and cell-free layer from the present continuum model show a good match with experiments and DPD simulations. For flow inside a tube with a constriction it is found that hematocrit depletion is greater downstream of the neck of the constriction. In addition, the effect of hematocrit loading on its distribution is correctly predicted. Finally, for a flow inside a tube with a bifurcation the average hematocrit concentration is found to be higher for the branch with the higher flow rate, thereby complying with the well-known bifurcation law.

A particle manipulation and sorting device using the dielectrophoretic (DEP) force is described in this study. The device consists of "ladder-type", "flip-type" and "oblique rail-type" electrode regions. The ladder-type and rail-type electrodes can generate a DEP force distribution that captures the particles, the DEP force of which is negative, in the area located at the center of the electrodes. The ladder-type electrode can align the particles with equal spacing in the streamwise direction. Using the flip-type electrode, which pushes the particles away, in combination with these electrodes, the direction of the particle and timing can be selected with high accuracy, reliability, and response. In the first half of this study, a numerical simulation is carried out to calculate the particle motion and evaluate the performance of the ladder-type electrode. Several models are used to investigate the influences of the non-uniformity of the electric field and the electric interaction of the surface charges and polarizations. Experiments are then carried out to demonstrate the motions of the particles and the sorting reliability. The trajectories and the probability density functions of the particles at the inlet and outlet of the electrode region showed that by using these electrodes the particles can be aligned, sorted, and guided accurately.

To understand the physical properties of lymphocytes and to develop a numerical model that can predict their motion and deformation in flows, a three-dimensional numerical simulation of lymphocytes flowing through the contraction region of a microchannel was performed using a compound drop model. The present model considers shear-thinning effects on the cytoplasm and the nucleus by modeling a second droplet inside the primary cell. The time-dependent characteristics of the deformation index (DI) of the lymphocyte, and the effects of the flow rate and the nucleus position on the DI are discussed and compared with the measurement. The results demonstrated that the conventional drop model, in which Newtonian fluid properties are applied to the cytoplasm, cannot correctly predict the deformation of the cell in the contraction region, where the nonlinear effects become important, whereas the compound drop model was consistent with experimental measurements of lymphocyte deformation. The size and position of the nucleus were found to influence the shape of the lymphocyte as measured by a change in the deformation rate of the leading and trailing sides of the lymphocyte. Further, a simplified model of lymphocyte deformation in the steady elongational flow was employed to determine the apparent viscosity, including the shear-thinning effects, of the lymphocyte., First online: 05 August 2015

A diethyl L-tartrate (L-EtTar)-assisted radical polymerization of N-vinyl-2-pyrrolidone has been developed as the first reported example of the synthesis of isotactic-rich poly(N-vinyl-2-pyrrolidone) (PVP). The addition of L-EtTar in toluene at temperatures of −40 °C and lower led to a significant increase in the polymer yield by one order of magnitude compared with the reaction in the absence of L-EtTar. Decreasing the polymerization temperature led to increases in the isotacticity of the PVP, with the mm triad reaching 66.4% at −93 °C. 1H NMR measurement at 920 MHz was conducted to establish a reliable strategy for quantifying the triad tacticities. High-temperature NMR measurements at 250 °C were performed using a specially-designed NMR probe, which led to dramatic narrowing of the 1H line width.

The microenvironment of cells, which includes basement proteins, shear stress, and extracellular stimuli, should be taken into consideration when examining physiological cell behavior. Although microfluidic devices allow cellular responses to be analyzed with ease at the single-cell level, few have been designed to recover cells. We herein demonstrated that a newly developed microfluidic device helped to improve culture conditions and establish a clonality-validated human pluripotent stem cell line after tracing its growth at the single-cell level. The device will be a helpful tool for capturing various cell types in the human body that have not yet been established in vitro.

A ceramic honeycomb was employed in a 1-kW class compact tubular fuel reformer based on noncatalytic partial oxidation (POX) of methanol. POX was stabilized on the outlet surface of the ceramic honeycomb under various experimental conditions with different equivalence ratios (φ) and thermal loads (qload); the latter represents the thermal input to the reformer calculated from the lower heating value (LHV) of methanol. The best performance of the reformer was achieved at φ = 3.5, and the adiabatic flame temperature was achieved. The location where the reaction occurred was determined, and the reaction was found to stabilize at an almost identical location under a wide range of thermal load conditions. This robust feature of the reaction is a significant characteristic of the ceramic honeycomb. By inserting a secondary honeycomb downstream of the reaction region, it was possible to move the reaction region upstream. This shifting of the reaction region was a result of the energy regeneration attributed to t...

A novel method that can measure the fluid temperature in microscopic scale by measuring the fluorescence polarization is described in this paper. The measurement technique is not influenced by the quenching effects which appears in conventional LIF methods and is believed to show a higher reliability in temperature measurements. Experiment was performed using a microchannel flow and fluorescent molecule probes, and the effects of the fluid temperature, fluid viscosity, measurement time, and pH of the solution on the measured fluorescence polarization degree are discussed to understand the basic characteristics of the present method. The results showed that fluorescence polarization is considerably less sensible to these quenching factors. A good correlation with the fluid temperature, on the other hand, was obtained and agreed well with the theoretical values confirming the feasibility of the method.

A microsensor that can continuously measure the deformability of a single red blood cell (RBC) in its microchannels using microelectrodes is described in this paper. The time series of the electric resistance is measured using an AC current vs. voltage method as the RBC passes between counter-electrode-type micro-membrane sensors attached to the bottom wall of the microchannel. The RBC is deformed by the shear flow created in the microchannel, the degree of deformation depends on the elastic modulus of the RBC. The resistance distribution, which is unique to the shape of the RBC, is analyzed to obtain the deformability of each cell. First, a numerical simulation of the electric field around the electrodes and RBC is carried out to evaluate the influences of the RBC height position, channel height, distance between the electrodes, electrode width, and RBC shape on the sensor sensitivity. Then, a microsensor was designed and fabricated on the basis of the numerical results. Resistance measurement was carried out using samples of normal RBCs and rigidified (Ca2+-A23186 treated) RBCs. Visualization measurement of the cells’ behavior was carried out using a high-speed camera, and the results were compared with those obtained above to evaluate the performance of the sensor.

The Sakhalin Slope Gas Hydrate Project (SSGH) is an international collaborative effort by scientists from Japan, Korea, and Russia to investigate natural gas hydrates (GHs) that have accumulated on the continental slope off Sakhalin Island, Okhotsk Sea. From 2009 to 2011, field operations of the SSGH-09, -10, and -11 projects were conducted. GH-bearing and -free sediment cores were retrieved using steel hydro- and gravity corers. The concentrations of sulfate ions in sediment pore waters were measured to investigate sulfate concentration–depth profiles. Seventeen cores showed linear depth profiles of sulfate concentrations. In contrast, eight cores and two cores showed concave-up and -down profiles plausibly explained by sudden increase and decrease in methane flux from below, respectively, presumably caused by the formation of gas hydrate adjacent to the core sampling sites.

The mixing and combustion performances of a baffle-plate-type millimeter-scale confined multi-jet were investigated experimentally by measuring the blow-off limit of the flames, exhaust gas components and two-dimensional unburned flow velocity profiles in a cylindrical chamber. Two types of multi-jet nozzle, parallel- and swirl-type nozzles, were examined in this study. In the parallel-type case, a small change in the distance between the fuel and air nozzles showed significant effects on the blow-off limit. When the air nozzles were closely located around the center of the chamber, the flame was easily extinguished and a pair of elongated flow recirculation was observed near the chamber sidewalls. When the distance was increased, large-scale reverse flows were observed in the central region that led to a stable and efficient combustion. In the swirl-type case, swirl flows made the flame more stable. Some cases of excessive swirl, however, deteriorate the fuel-and-air mixing performance and increase the CO concentration.

A three-dimensional numerical simulation was carried out to examine the effects of swirl and buoyancy-driven flows on the mixing performance of a baffle-plate-type miniature confined multijet. Swirl flow was produced by inclining the jet nozzles surrounding the central jet in the circumferential direction. The results obtained were compared with those of the non-swirl case. The swirl flow interrupted the radial secondary flow generated in the region adjacent to the baffle plate. This interruption decreased the size of the reverse flow region, resulting in a deterioration of the mixing performance. This behavior was more noticeable in the case of a large swirl number. During the study of the buoyancy effect, the operating direction of the gravitational force was changed with respect to the central axis of the mixing chamber, i.e. the attack angles were 0°, 90° and 180°. The buoyancy effect was negligible when the operating direction was parallel to the chamber axis. However, when the attack angle was 90°, asymmetric distributions of mixture fraction and flow velocity were obtained, and the mixing performance was found to be poor. In the swirl-accompanied cases, the effect of buoyancy force was apparent even when the operating direction was parallel to the central axis. The swirl flow, which reduced the secondary flow effects of the reverse and radial flows, tended to increase the effect of the buoyancy force on the multijet flow. On the other hand, the swirl flow prevented the mixture fraction distribution to be asymmetric in the case of buoyancy with 90° attack angle. These tendencies became more conspicuous for flows with stronger swirl.

A sensor that can efficiently and sequentially measure the deformability of individual red blood cell (RBC) flowing along a microchannel is described. Counter-electrode-type microsensors are attached to the channel bottom wall, and as RBCs pass between the electrodes, the time series of the electric resistance is measured. An RBC is deformed by the high shear flow to a degree dependent upon its elastic modulus. Hence, the profile of the resistance, which is unique to the shape of the RBC, can be analyzed to obtain the deformability of each cell. First, theoretical and experimental analyses were conducted to identify the specific AC frequency at which the effect of the electric double layer formed on the electrode surface is minimized. Measurements were then conducted upon samples of normal human RBCs and glutaraldehyde-treated (rigidified) RBCs to evaluate the feasibility of the present method. In addition, simultaneous visualization of RBC deformation was performed using a high-speed camera. Normal RBCs were observed to have a degree of deformation index (DI) of around 0.57, whereas the rigidified RBCs was DI = 0 in the microchannel. The experimental measurements showed a strong correlation between the half-width of the maximum of the resistance distribution and the DI of the RBC.