Magnetic resonance imaging of reaction-driven viscous fingering in a packed bed

► Viscous fingering is investigated in a reactive system in a 3D porous medium using MRI. ► Wormlike micelles form between solutions of CTAB and NaSal in a packed bed. ► Fingering patterns are formed by an interfacial instability. ► This chemical system shares similarities with biofilm formation in porous media. ► Fingering patterns were characterized through statistical analysis of the MR images.