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Cell is the fundermental unit of life. The research about cells has always beenthe hot topic in biological fields. Cell separation is an indispensible part in cellresearch, and it is the prerequisite of cell culturing and dignosising some diseases.
In recent years, microfluidics have brought great convinience to cell separation,therefore large numbers of people devote themselves to study methods of cellisolation. Pinched Flow Fractionation, due to its simple manipulation and highapplication scope, has drawn research scholars' attention, since introduced.
In this paper, we are going to employ immersed boundary-lattice Boltzmannmethod to study Pinched Flow Fractionation, and lattice Boltzmann method isutilized to construct fluid field and immersed boundary method is used to simulatethe interaction between cells and fluid.
Firstly, the model and methods emploied in this paper are validated carefully.
The validation are based on three aspects: （1） validation of lid-driven cavity flow;（2） validation of two-dimensional Poiseuille flow; （3） validation of flow around acircular cylinder. By comparing the simulational results with previous results, it iscan be concluded that the methods and models can simulate the fluid flowaccurately.
Moreover, the separation performances of different conditions are studied. Theseparation effects at low Reynolds number （about 1） of different pinched segmentwidths, flow ratios, and cell membrane stiffness are discussed, and the cell bandingpheonomenon is investigated.
The conclusions are following:
（1）The pinched segment width can influence the isolation performancetremendously, In most cases, decreasing the pinced segment width can improve theseparation performances.
（2）In order to separate two kinds of cells, the diluted flow rate must be morethan that of particle solution. Enlarging the diluted flow rate can enchance theseparation performances. However, when the diluted flow rate increases to somevalue, it is not effective any more to improve the isolation effects.
（3）The empirical formula can predict the outflow postions of cells. But whencells are too flexible, the formula will be not so effective.
（4）When the distance between two cells are too small, cell banding will occur.
And also, the relative position between two cells will influence the separtion effectas well. With the increase of distance between two cells, approximate isolationresults are obtained when small cell is in the front, back and left position of largecell. However, a better separation performance can be got when small cell is in theright postion of large cell.
