We have examined the fundamental mechanisms which drive the varied beh
aviors of advancing surfactant solutions. We show that surfactant conc
entration gradients and solution mobility are required for dendritic s
preading, which occurs when an ionic surfactant,spreads on a surface o
f the same charge. When the surfactant has the opposite charge as the
ionized substrate, it can strongly adsorb to the surface ahead of the
advancing solution. Inhibition of the fluid advance by surfactant-adso
rption at the contact line alters the dendritic pattern and can change
the spreading to stick-jump motion. By tuning the strength of the sur
factant-surface interaction, we have observed a spectrum of spreading
behaviors from dendritic to stick-jump.