Fig. 4: Dynamic cell trapping and size-based separation.

a The stacked images demonstrate the trapping process of the single cell in different initial positions via SteAST. The graph shows the velocity spectrum of individual cells in the trapping process. The trapping process is divided into three stages: the lateral flow zone (region (a)), focus zone (region (b)), and buffering zone (region (c)). The cells are finally captured at the trapping point. b The trajectory of trapped single HeLa cells in diluted blood. The stacked image is created by merging 41 frames. The graph shows the velocity spectrum of trapped single HeLa cells. c Capture efficiency of HeLa cells stained with calcein-AM (Invitrogen, USA) at different applied powers and flow rates. The fluorescence field was observed, the number of cells trapped by SteAST and the number of cells flowing through were counted, and the capture efficiency was calculated based on the ratio of the two. d The relationship among the number of trapped cells (capture capacity), applied power and flow rate. The images show the expansion of the trapping position as the power increased. e Digital release of the trapped cell. Multiple cells (2, 3, 4 HeLa cells dyed by calcein-AM) are trapped in SteAST, and the digital controllable release of the individual cells one by one is achieved by gradually reducing the power to regulate the capturing capacity. f Selective trapping of HeLa cells (CTCs) in undiluted whole blood. (f-1) Hydrodynamic focusing of a whole blood sample. (f-2) Blood cells release when the power is turned on. (f-3) ~ (f-5) Selective trapping of individual CTCs. The stacked image sequences demonstrate the trajectories of trapped CTCs. (f-6) The merged image shows that the three CTCs were stably trapped while the blood cells were released from SteAST. The ratio of double focusing fluid and cell fluid is 1:1:1. The total flow rate was 1 µL/min. The scale bars are 100 μm.