Fig. 2.

Simulation results showing the flow velocity profiles and particle trajectories in the trapping channels when valve is deactivated (A) and when valve is activated (B). Flow velocity magnitude (m/s) is shown in (i). Insets show the streamlines of the velocity field. Particle trajectories in the trapping channels at different time points after particles being released at the inlet are shown in (ii–iv). Boundary conditions: inlet velocity is set to be 100 μm/s; outlet pressure is set to be 0 Pa; walls are set to the ‘No slip’ wall boundary condition. One hundred particles (diameter = 10 μm; density = 1050 kg/m³) are released at the inlet of the channel and driven by the drag force of the fluid. It should be noted that the time-dependent particle tracing simulation is only used to demonstrate the fluid dynamics. The particles released in the simulation are virtual, therefore would not be stopped by the mechanical trap. The particle tracing simulation is used to calculate the probabilities of particles flowing into the trap and into the bypass.