Dye the cells to be tested and make single cell suspension. The sample to be tested is pressed into the flow chamber at a certain pressure, and the phosphate buffer solution without cells is ejected from the sheath fluid tube at a high pressure. The inlet direction of the sheath fluid tube forms a certain angle with the flow direction of the sample to be tested, so that the sheath fluid can flow around the sample at a high speed to form a circular flow, and the cells to be tested are lined up under the sheath fluid and pass through the detection area in turn.

Flow cytometry usually uses laser as light source. The focused and shaped beam is vertically irradiated on the sample flow, and the cells dyed by fluorescence generate scattered light and excited fluorescence under the irradiation of the laser beam. These two signals are simultaneously received by forward photodiode and photomultiplier tube in 90 direction. The light scattering signal is detected at a small forward angle, which basically reflects the size of the cell. The receiving direction of the fluorescence signal is perpendicular to the laser beam, and after being separated by a series of dichroic mirrors and bandpass filters, a plurality of fluorescence signals with different wavelengths are formed.

The intensity of these fluorescent signals represents the intensity of antigen on the surface of cell membrane or the concentration of substances in its nucleus. After being received by photomultiplier tube, they can be converted into electrical signals, and then converted into digital signals that can be recognized by computer through A/D converter. The computer processes the measured signals, displays the analysis results on the computer screen, prints them out, and stores them on the hard disk in the form of data files for future inquiry or further analysis.

Depending on different measurement parameters, the display of test data can be selected in various forms. Single-parameter data is expressed in the form of histogram, and its X axis is measured intensity and Y axis is cell number. Generally speaking, the resolution of flow cytometry coordinate axis is 5 12 or 1024 channels, which depends on the resolution of its analog-to-digital converter. For two-parameter or multi-parameter data, the histogram of each parameter can be displayed separately, and two-dimensional three-point map, contour map, gray scale map or three-dimensional stereo map can also be selected.

Cell sorting is achieved by separating droplets containing a single cell. The nozzle of the flow chamber is equipped with an UHF transistor, which vibrates after charging, so that the ejected liquid flow is broken into uniform droplets, and the cells to be detected are dispersed in these droplets. These droplets have different positive and negative charges. When the droplets flow through the deflection plate of several thousand volts, they are deflected under the action of high-voltage electric field and fall into their respective collection containers, and the uncharged droplets fall into the middle waste container, thus realizing cell separation.