Hydrodynamic Focusing: Channel Design - Jingqiao Shen

Mainstream Radius, Side Stream Radius, and Shape Design

Figure 1: Present design of hydrodynamic focusing device^[1]

The study Nagi et al. proposed a model, uses circular cross section sample inlet and surrounded by conical shaped sheath inlet, to study the optimum conditions for the system to have the best hydrodynamic focusing^[1]. The COMSOL program was used by the researcher for simulation

Firstly, with the fixed channel overall length and radius of sample inlet, they examined the effects of sample to sheath flow velocity ratio and the radius of conical sheath inlet^[1]. Result in figure 2 showed that the focusing width ratio decreased as the radius of conical sheath inlet increased, which promoted the more focused channel for ions to pass through; the velocity ratio showed that the higher sheath flow velocity, the ion can be more focused. In the second part, they examined the effects of velocity ratio and the radius of sample inlet. Similar results were displayed that the increase of focusing width ratio led to the less focused channel, and higher velocity ratio led to the more focused channel.

Figure 2: Performances of hydrodynamic focusing by different radius of conical sheath inlet and flow velocity ratio^[1]

In addition, they compared their model to the Vakilzadeh and Kamali‘s model(square cross section sample inlet and column shaped sheath inlet) with same channel volume, sheath cross section area, and flow velocity ratio^[1][6]. The ion concentration peak of the proposed model has a higher value than Vakilzadeh's model; also, the present model has a more focused channel than Vakilzadeh’s model.

Figure 3: Comparison of present model and Vakilzadeh and Kamali‘s model^[6]

Side Channel Design: Successive and Simultaneous

Study from Nagi et al. showed that the successive model has a smaller focusing width than the simultaneous model^[3]. Other 3 methods to decrease the focusing width are: 1. Decreasing the angle between sample and sheath flow to 60^oC or less; 2. Decreasing the radius of sample inlet and sheath inlet; 3. Decreasing the sample to sheath flow velocity ratio^[3].

References

[1] Nagi, M. A.; Elbeheiry, N. A.; Afify, R. S.; Shershira, H. M. A Novel Full Hydrodynamic Focusing Design in Flow Cytometer. In 2018 9th Cairo International Biomedical Engineering Conference (CIBEC); IEEE, 2018; pp 102–105.

[2] Al-Zareer, M. Tunable Hydrodynamic Focusing with Dual-Neodymium Magnet-Based Microfluidic Separation Device. Med. Biol. Eng. Comput. 2022, 60 (1), 47–60. https://doi.org/10.1007/s11517-021-02438-3.

[3] Nagi, M. A.; Elbeheiry, N. A.; Shershira, H. M. Simultaneous and Successive Three Dimensional Hydrodynamic Focusing in Flow Cytometer. In 2018 9th Cairo International Biomedical Engineering Conference (CIBEC); IEEE, 2018; pp 29–32.

[4] Kim, D. S.; Kim, D. S. (danny); Han, K.; Yang, W. An Efficient 3-Dimensional Hydrodynamic Focusing Microfluidic Device by Means of Locally Increased Aspect Ratio. Microelectron. Eng. 2009, 86 (4–6), 1343–1346. https://doi.org/10.1016/j.mee.2009.01.017.

[5] Wang, Y.-Q.; Wang, J.-Y.; Chen, H.-L.; Zhu, Z.-C.; Wang, B. Prototype of a Novel Micro-Machined Cytometer and Its 3D Hydrodynamic Focusing Properties. Microsyst. Technol. 2012, 18 (12), 1991–2001. https://doi.org/10.1007/s00542-012-1525-x.

[6] A. H. Vakilzadeh and R. Kamali, ―A novel hydrodynamic focusing microdevice for flow cytometry applications,‖ Iran. J. Sci. Technol. - Trans. Mech. Eng., vol. 38, no. M2, pp. 361–373, 2014