Efficient Separation of Methanol Single-Micron Droplets by Tailing Phenomenon Using a PDMS Microfluidic Device.

Microdroplet-based fluidic systems have the advantages of small size, short diffusion time, and no cross-contamination; consequently, droplets often provide a fast and precise reaction environment as well as an analytical environment for individual molecules. In order to handle diverse reactions, we developed a method to create organic single-micron droplets (S-MDs) smaller than 5 µm in diameter dispersed in silicone oil without surfactant. The S-MD generation microflow device consists of a mother droplet (MoD) generator and a tapered separation channel featuring multiple side channels. The tapered channel enhanced the shear forces to form tails from the MoDs, causing them to break up. Surface treatment with the fluoropolymer CYTOP protected PDMS fluid devices from organic fluids. The tailing separation of methanol droplets was accomplished without the use of surfactants. The generation of tiny organic droplets may offer new insights into chemical separation and help study the scaling effects of various chemical reactions.

Efficient Synthesis of a Schiff Base Copper(II) Complex Using a Microfluidic Device.

The efficient synthesis of amino acid Schiff base copper(II) complexes using a microfluidic device was successfully achieved. Schiff bases and their complexes are remarkable compounds due to their high biological activity and catalytic function. Conventionally, products are synthesized under reaction conditions of 40 °C for 4 h using a beaker-based method. However, in this paper, we propose using a microfluidic channel to enable quasi-instantaneous synthesis at room temperature (23 °C). The products were characterized using UV-Vis, FT-IR, and MS spectroscopy. The efficient generation of compounds using microfluidic channels has the potential to significantly contribute to the efficiency of drug discovery and material development due to high reactivity.

High-Efficiency Single-Cell Containment Microdevices Based on Fluid Control.

In this study, we developed a comb-shaped microfluidic device that can efficiently trap and culture a single cell (bacterium). Conventional culture devices have difficulty in trapping a single bacterium and often use a centrifuge to push the bacterium into the channel. The device developed in this study can store bacteria in almost all growth channels using the flowing fluid. In addition, chemical replacement can be performed in a few seconds, making this device suitable for culture experiments with resistant bacteria. The storage efficiency of microbeads that mimic bacteria was significantly improved from 0.2% to 84%. We used simulations to investigate the pressure loss in the growth channel. The pressure in the growth channel of the conventional device was more than 1400 PaG, whereas that of the new device was less than 400 PaG. Our microfluidic device was easily fabricated by a soft microelectromechanical systems method. The device was highly versatile and can be applied to various bacteria, such as Salmonella enterica serovar Typhimurium and Staphylococcus aureus.

Development of Measurement Method for Temperature and Velocity Field with Optical Fiber Sensor.

We have developed a new method for measuring temperature and velocity at a high spatial resolution (minimum 2.56 mm pitch along an optical fiber). The developed method uses the same principle as a hot wire anemometer, where the velocity perpendicular to an optical fiber is estimated as a function of the cooling curve of a gold-coated layer on the optical fiber Joule-heated intermittently. The developed optical fiber sensor demonstrated the ability to acquire a transient velocity profile in airflow experiments with high repeatability and accuracy. This paper describes optical fiber-based velocity measurement in the velocity range of approximately 0-7 m/s with an error of approximately 10% compared to a hot wire anemometer and a new method for simultaneous temperature and velocity measurements. Applicability to velocity distribution measurements and seconds transient velocity changes are also described.

Head Injury Assessment in the Elite Level Rugby Union in Japan: Review of 3 Seasons.

Head Injury Assessment (HIA) is the screening tool for head injury during a rugby game. The purpose of this study was to investigate the epidemiology of HIA in the Japan Rugby Top League (JRTL). The incidences of HIA, defined concussion (per 1,000 player-hours) and repeated concussions were evaluated in three seasons (2016-17, 2017-18, 2018-19; total 360 games). The HIA incidence rates were 12.7 (95% confidence interval 9.5-15.9), 20.8 (16.8-24.9), and 25.0 (20.5-29.5) in each season. HIA-1 criteria 2, which is applied for suspected concussion cases, was performed for 46 cases in the 2016-17 season, 81 cases in the 2017-18 season, and 88 cases in the 2018-19 season. The concussion incidence rates were significantly greater in the 2017-18 season (9.6/1000 player-hours, 95% confidence interval 6.8-12.4) and the 2018-19 season (14.4, 11-17.8) compared to the 2016-17 season (4.8, 2.8-6.8). The number of repeated concussion cases in the same season was 1 in the 2016-17 season and 4 in both the 2017-18 and 2018-19 seasons. This study confirmed significantly higher HIA and concussion incidence rates over time. Although the HIA system might have been established in the three seasons in JRTL, comprehensive management needs to be improved to prevent repeated concussions.

Efficient Generation of Microdroplets Using Tail Breakup Induced with Multi-Branch Channels.

In recent years, research on the application of microdroplets in the fields of biotechnology and chemistry has made remarkable progress, but the technology for the stable generation of single-micrometer-scale microdroplets has not yet been established. In this paper, we developed an efficient and stable single-micrometer-scale droplet generation device based on the fragmentation of droplet tails, called "tail thread mode", that appears under moderate flow conditions. This method can efficiently encapsulate microbeads that mimic cells and chemical products in passively generated single-micrometer-scale microdroplets. The device has a simple 2D structure; a T-junction is used for droplet generation; and in the downstream, multi-branch channels are designed for droplet deformation into the tail. Several 1-2 µm droplets were successfully produced by the tail's fragmentation; this continuous splitting was induced by the branch channels. We examined a wide range of experimental conditions and found the optimal flow rate condition can be reduced to one-tenth compared to the conventional tip-streaming method. A mold was fabricated by simple soft lithography, and a polydimethylsiloxane (PDMS) device was fabricated using the mold. Based on the 15 patterns of experimental conditions and the results, the key factors for the generation of microdroplets in this device were examined. In the most efficient condition, 61.1% of the total droplets generated were smaller than 2 µm.

Controlling Microdroplet Inner Rotation by Parallel Carrier Flow of Sesame and Silicone Oils.

We developed a method for passively controlling microdroplet rotation, including interior rotation, using a parallel flow comprising silicone and sesame oils. This device has a simple 2D structure with a straight channel and T-junctions fabricated from polydimethylsiloxane. A microdroplet that forms upstream moves into the sesame oil. Then, the largest flow velocity at the interface of the two oil layers applies a rotational force to the microdroplet. A microdroplet in the lower oil rotates clockwise while that in the upper oil rotates anti-clockwise. The rotational direction was controlled by a simple combination of sesame and silicone oils. Droplet interior flow was visualized by tracking microbeads inside the microdroplets. This study will contribute to the efficient creation of chiral molecules for pharmaceutical and materials development by controlling rotational direction and speed.

Density and viscosity of liquid ZrO2 measured by aerodynamic levitation technique.

Liquid ZrO2 is one of the most important materials involved in severe accident analysis of a light-water reactor. Despite its importance, the physical properties of liquid ZrO2 are scarcely reported. In particular, there are no experimental reports on the viscosity of liquid ZrO2. This is mainly due to the technical difficulties involved in the measurement of thermo-physical properties of liquid ZrO2, which has an extremely high melting point. To address this problem, an aerodynamic levitation technique was used in this study. The density of liquid ZrO2 was calculated from its mass and volume, estimated based on the recorded image of the sample. The viscosity was measured by a droplet oscillation technique. The density and viscosity of liquid ZrO2 at temperatures ranging from 2753 K to 3273 K, and 3170 K-3471 K, respectively, were successfully evaluated. The density of liquid ZrO2 was found to be 4.7 g/cm 3 at its melting point of 2988 K and decreased linearly with increasing temperature, and the viscosity of liquid ZrO2 was 13 mPa at its melting point.

Comparison of 12- and 16-core prostate biopsy in japanese patients with serum prostate-specific antigen level of 4.0-20.0 ng/mL.

PURPOSE: In the present study, we compared 12- with 16-core biopsy in patients with prostate- specific antigen (PSA) levels of 4.0-20.0 ng/mL. MATERIALS AND METHODS: Between 2003 and 2010, 332 patients whose serum PSA level was between 4.0 and 20.0 ng/mL underwent initial transrectal ultrasound (TRUS)-guided needle biopsy. Of those patients, 195 underwent 12-core biopsy and 137 underwent 16-core biopsy. RESULTS: In the 12-core prostate biopsy group, 66 (33.8%) patients were found to have prostate cancer. On the other hand, in the 16-core prostate biopsy group of 137 patients, 61 (44.5%) were found to have prostate cancer. Among all patients, the prostate cancer detection rate was slightly higher in the 16-core biopsy group than in the 12-core biopsy group. Moreover, in patients with prostate volume > 30 mL or PSA density (PSAD) < 0.2, the prostate cancer detection rate was significantly higher in the 16-core biopsy group than in the 12-core biopsy group. There was no significant difference in pathological tumor grade, indolent cancer probability, or biopsy complication rate between the two groups. CONCLUSION: In order to detect prostate cancer, 16-core prostate biopsy is safe and feasible for Japanese patients with serum PSA level of 4.0-20.0 ng/mL.