Figure 4.

Finite-element modeling (FEM) of the device. (a) A two-dimensional FEM simulation (in COMSOL) of a vertical cross-section passing through a single microjet and the chamber, showing the concentration profile of netrin-1 (color map) and the flow velocity in the chamber (black arrows, with the arrow-heads indicating the flow direction and with the length proportional to the magnitude of the flow velocity). In this particular simulation, the flow rate through a single microjet was 2.30 pL s⁻¹ (which corresponded to a flow rate of 100 μL h⁻¹ through the entire device). (b) A plot of the fluidic shear stress exerted on the surface of the chambers for different flow rates through the device. The dotted line denotes the shear stress limit (0.012 dynes per cm²) that elicits turning in mammalian growth cones. (c) A plot of the steady-state concentration profiles of netrin-1, 10 μm above the surface of the chamber, for different flow rates.