Flow focusing with viscoelastic liquids

AbstractOptical-based microfluidic cell sorting has become increasingly attractive for applications in life and environmental sciences due to its ability of sophisticated cell handling in flow. The majority of these microfluidic cell sorting devices employ two-dimensional fluid flow control strategies, which lack the ability to manipulate the position of cells arbitrarily for precise optical detection, therefore resulting in reduced sorting accuracy and purity. Although three-dimensional (3D) hydrodynamic devices have better flow-focusing characteristics, most lack the flexibility to arbitrarily position the sample flow in each direction. Thus, there have been very few studies using 3D hydrodynamic flow focusing for sorting. Herein, we designed a 3D hydrodynamic focusing sorting platform based on independent sheath flow-focusing and pressure-actuated switching. This design offers many advantages in terms of reliable acquisition of weak Raman signals due to the ability to precisely control the speed and position of samples in 3D. With a proof-of-concept demonstration, we show this 3D hydrodynamic focusing-based sorting device has the potential to reach a high degree of accuracy for Raman activated sorting.

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Subthreshold laser jetting via flow-focusing in laser-induced forward transfer

Physical Review Fluids ◽

10.1103/physrevfluids.3.082201 ◽

2018 ◽

Vol 3 (8) ◽

Cited By ~ 3

Author(s):

Emre Turkoz ◽

SeungYeon Kang ◽

Luc Deike ◽

Craig B. Arnold

Keyword(s):

Flow Focusing ◽

Forward Transfer ◽

Subthreshold Laser

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Effect of heat source on Rayleigh–Bénard convection in rotating viscoelastic liquids

Heat Transfer ◽

10.1002/htj.22248 ◽

2021 ◽

Author(s):

G. Jayalatha ◽

N. Suma

Keyword(s):

Heat Source ◽

Bénard Convection ◽

Benard Convection ◽

Viscoelastic Liquids ◽

Rayleigh Benard Convection ◽

Rayleigh Benard

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Study on External Gas-Assisted Mold Temperature Control with the Assistance of a Flow Focusing Device in the Injection Molding Process

Materials ◽

10.3390/ma14040965 ◽

2021 ◽

Vol 14 (4) ◽

pp. 965 ◽

Cited By ~ 1

Author(s):

Nguyen Truong Giang ◽

Pham Son Minh ◽

Tran Anh Son ◽

Tran Minh The Uyen ◽

Thanh-Hai Nguyen ◽

...

Keyword(s):

Injection Molding ◽

Temperature Control ◽

Mold Temperature ◽

Injection Molding Process ◽

Melt Flow ◽

Flow Focusing ◽

Molding Process ◽

Heating Efficiency ◽

Flow Length ◽

Insert Plate

In the injection molding field, the flow of plastic material is one of the most important issues, especially regarding the ability of melted plastic to fill the thin walls of products. To improve the melt flow length, a high mold temperature was applied with pre-heating of the cavity surface. In this paper, we present our research on the injection molding process with pre-heating by external gas-assisted mold temperature control. After this, we observed an improvement in the melt flow length into thin-walled products due to the high mold temperature during the filling step. In addition, to develop the heating efficiency, a flow focusing device (FFD) was applied and verified. The simulations and experiments were carried out within an air temperature of 400 °C and heating time of 20 s to investigate a flow focusing device to assist with external gas-assisted mold temperature control (Ex-GMTC), with the application of various FFD types for the temperature distribution of the insert plate. The heating process was applied for a simple insert model with dimensions of 50 mm × 50 mm × 2 mm, in order to verify the influence of the FFD geometry on the heating result. After that, Ex-GMTC with the assistance of FFD was carried out for a mold-reading process, and the FFD influence was estimated by the mold heating result and the improvement of the melt flow length using acrylonitrile butadiene styrene (ABS). The results show that the air sprue gap (h) significantly affects the temperature of the insert and an air sprue gap of 3 mm gives the best heating rate, with the highest temperature being 321.2 °C. Likewise, the actual results show that the height of the flow focusing device (V) also influences the temperature of the insert plate and that a 5 mm high FFD gives the best results with a maximum temperature of 332.3 °C. Moreover, the heating efficiency when using FFD is always higher than without FFD. After examining the effect of FFD, its application was considered, in order to improve the melt flow length in injection molding, which increased from 38.6 to 170 mm, while the balance of the melt filling was also clearly improved.

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Purely elastic instabilities in a microfluidic flow focusing device

Physical Review Fluids ◽

10.1103/physrevfluids.2.053301 ◽

2017 ◽

Vol 2 (5) ◽

Cited By ~ 4

Author(s):

P. Ballesta ◽

M. A. Alves

Keyword(s):

Flow Focusing ◽

Microfluidic Flow ◽

Elastic Instabilities

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Negative Pressure Provides Simple and Stable Droplet Generation in a Flow-Focusing Microfluidic Device

Micromachines ◽

10.3390/mi12060662 ◽

2021 ◽

Vol 12 (6) ◽

pp. 662

Author(s):

Nikita A. Filatov ◽

Anatoly A. Evstrapov ◽

Anton S. Bukatin

Keyword(s):

Microfluidic Device ◽

Negative Pressure ◽

Low Cost ◽

Control Valve ◽

Droplet Microfluidics ◽

Droplet Generation ◽

Electric Signal ◽

Absolute Pressure ◽

Flow Focusing ◽

Wide Range

Droplet microfluidics is an extremely useful and powerful tool for industrial, environmental, and biotechnological applications, due to advantages such as the small volume of reagents required, ultrahigh-throughput, precise control, and independent manipulations of each droplet. For the generation of monodisperse water-in-oil droplets, usually T-junction and flow-focusing microfluidic devices connected to syringe pumps or pressure controllers are used. Here, we investigated droplet-generation regimes in a flow-focusing microfluidic device induced by the negative pressure in the outlet reservoir, generated by a low-cost mini diaphragm vacuum pump. During the study, we compared two ways of adjusting the negative pressure using a compact electro-pneumatic regulator and a manual airflow control valve. The results showed that both types of regulators are suitable for the stable generation of monodisperse droplets for at least 4 h, with variations in diameter less than 1 µm. Droplet diameters at high levels of negative pressure were mainly determined by the hydrodynamic resistances of the inlet microchannels, although the absolute pressure value defined the generation frequency; however, the electro-pneumatic regulator is preferable and convenient for the accurate control of the pressure by an external electric signal, providing more stable pressure, and a wide range of droplet diameters and generation frequencies. The method of droplet generation suggested here is a simple, stable, reliable, and portable way of high-throughput production of relatively large volumes of monodisperse emulsions for biomedical applications.

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