In this study, the effects of polymer flexibility and entanglement on elastic instability were investigated by observing sodium hyaluronate (Hyaluronic Acid Sodium salt, Na-HA) solution in planar abrupt contraction-expansion microchannels. The rigidity of Na-HA in a solution is affected by ion concentration in the solution. Therefore, we prepared Na-HA water solution and Na-HA PBS solution with concentrations from 0.15 wt% to 0.45 wt%. The rheological properties were measured and analyzed to detect the Na-HA overlap and entanglement concentrations. The flow regimes of the Na-HA solutions in several planar abrupt contraction-expansion channels were characterized in terms of rheological properties, polymer flexibility and polymer entanglement.
We present a numerical simulation method based on phase-field model and immersed boundary method for permeation of oil-in-water (O/W) emulsion through fibrous filter in coalescer process. First, the effects of the wettability of fibers and filter porosity on the coalescing dynamics are investigated by the simulations of O/W emulsions permeating through modeled fibrous filters. The simulation results reveal that the highly hydrophilic fiber surface brings about the generation of small secondary droplets during detachment from the filter. In addition, the large pore spacing promotes the formation of larger droplets but increases the number of uncoalesced droplets. Then, to represent a realistic flow field inside the fibrous filters during simulation, a numerical method that coordinates the filter structure obtained by X-ray CT imaging is developed. The simulation demonstrates that the arrangement of closely attached fibers at the permeate side surface of the filter enhances the formation of large droplets.
We propose a microfluidic process to prepare monodisperse microcapsules possessing a large aqueous core and a hydrogel membrane shell through the formation of aqueous two-phase system droplets with dextran-rich core and tetra-PEG-rich shell and subsequent cross-linking reaction in the shell. This microfluidic approach can continuously produce the microcapsules from water-in-oil emulsion droplets under mild conditions without the use of radical initiators and external energy such as heat and ultraviolet light. In addition, the size and thickness of the microcapsules can be controlled separately by changing flow conditions upon microfluidic emulsification. In this paper, authors will introduce the detailed preparation procedure of the microcapsules.
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.
For playing a role of filling a hole in the applicable range of standard rheometer, ultrasonic spinning rheometry (USR) is presented; it is based on equation of motion to explain the fluid rheology and to quantify the rheological properties satisfying the considered equation of motion for complex fluids. Some examples of rheological evaluation for multi-phase fluids using USR were presented; clay dispersion with thixotropy, polymer solution with large-spherical particles, dessert paste with pectin gel including fruit pulps. The efficacy of USR was discussed through those practical tests for complex fluid.
In view of the importance of one-dimensional thermal-hydraulic analysis for rod bundle geometry, extensive efforts to improve constitutive equations have been made in recent years. In the present review article, state-of-the-art of the rod-bundle constitutive equations for flow regime map, void fraction, covariance, and interfacial area concentration models is reviewed. Among them, the constitutive relations for covariance and interfacial area concentration models may have the potential to improve the robustness of the conventional analysis method. Some sensitivity analysis results using TRAC-BF1 code with the new constitutive equations are summarized and reviewed.
Micro bubbles measuring tens of micrometers or less in diameter have recently been paid much attention. Swirl type, pressurizing dissolution, and perforated plate methods have been proposed for micro bubble generation. The swirl type method can generate micro bubbles even under low-pressure power in a simple structure. This study examined the effect of the swirl chamber inlet diameter on the bubble diameter in a swirl type micro bubble generator. The swirl chamber inlet diameter was varied in the range of 15-90 mm and the effect was examined. In order to clarify the effect of enlarged inlet diameter, the micro bubbles diameter was measured under changing water supply pressure and air flow rate, the behavior of air column in the swirl chamber was visualized, and the velocity distribution around outlet of swirl chamber was measured. As a result, when the swirl chamber inlet diameter was enlarged, the outflow form changed from an axial outflow to a radial outflow. The average bubble diameter could also be reduced. An average bubble diameter of 28 μm could be realized under the conditions of swirl inlet diameter of 90 mm and water supply pressure of 0.1 MPa gage.