Fig. 1. Working principles of commercial flow cytometry. (a) Conventional flow cytometry^[22]; (b) Amnis ImageStream imaging flow cytometry^[21]

Fig. 2. Optical design of camera-based IFC. (a) MIFC^[23]; (b) using a pseudo-random excitation pulse sequence as illumination source to eliminate motion blur^[24]; (c) virtual-freezing fluorescence imaging flow cytometry^[26]

Fig. 3. Optical design of PMT-based IFC. (a) Serial time-encoded amplified microscope^[32]; (b) captured cell images using spatial-temporal transformation^[35]

Fig. 4. Optical design of 3D IFC. (a) Fast scanning of illumination light source combined with spatial-temporal transformation to capture fluorescence and side scattering images^[47]; (b) using Mach‒Zehnder interferometer to detect wavefront distortion and generate a 3D refractive index map of cells^[48]

Fig. 5. System design of intelligent IACS, which can perform real-time sorting based on image features of the cells^[75]

Fig. 6. Another example of image activated cell sorter^[79]. (a) Design of optical imaging system; (b) schematic diagram of signal processing pipeline

Fig. 7. Major applications of IFC/IACS. A few examples include plant and marine biology, tumor cell killing, cell‒cell interaction, label-free assays, biomarker colocalization, and subcellular translocation