Studying the kinetics of thiols' self-assembled monolayer formation in microfluidic channels

The kinetics of microfluidic-based thiolic self-assembled monolayer (SAM) formation on the metallic surfaces has been studied through numerical simulation. The computational model simultaneously solves the equations of thiols' mass transport, a two-dimensional diffusion-convection, coupled to the one-dimensional self-assembly on the metallic surface. The model is employed in examining the effect of input thiol concentration and flow velocity on the kinetics, as well as studying the effect of change in microchannel height and thiols' packing density. In addition, the SAM kinetics in pressure and electrokinetically driven flows are compared to each other. Dimensionless groups are used to compare the reaction and fluidic phenomena present and explain the trends observed in the numerical simulations. Except the concentration, other parameters were observed to impose minor impacts on the kinetics. Namely, simulation results confirmed the possibility of achieving a 15-min self-assembly period versus the conventional 24-h process time. However, due to reaction-limited nature of thiols self-assembly use of microfluidics cannot help in achieving a considerably faster kinetics. The result of the numerical simulation is verified by an analytical model and compared to experimental data in the literature.