Concentration at cell surface as a function of x, in units of nmol∕cm3: single channel (dotted and dashed lines) vs bilayer (solid black line). For the bilayer, the cell compartment flow rate is given by QI=2.5 nL∕s (τ=0.3 dyne∕cm2), while the flow channel flow rate is given by QII=25 nL∕s. For the single channel, we have flow rates given by Q=2.5 nL∕s, corresponding to τ=0.3 dyne∕cm2 (dashed black line) and Q=25 nL∕s, corresponding to τ=3.0 dyne∕cm2 (dotted blue line). For the single channel case corresponding to τ=0.3 dyne∕cm2, note the decaying concentration profile, while the bilayer concentration profile is, except for a small depletion zone at the beginning of the channel, nearly uniform. Other parameters are those for Case 2.