Capillary Flow of Wormlike Micellar Gels

Wormlike micellar solutions formed by long-chained zwitterionic surfactants show gel-like rheology at room temperature and have recently been found to exhibit other complex rheological features. We study the capillary flow of these wormlike micellar gels to uncover rheological fingerprints on a canonical flow scenario and calculate shear viscosity at high shear rates. We quantify pressure drop for a range of flow rates to see if micelles undergo a structural transition that reflects on the viscosity vs shear rate scaling. We also use optical coherence tomography-based velocimetry to ascertain if there are flow rate-driven transitions in velocity profiles. Our experiments shed light on the fluid dynamics of wormlike micelles and other complex fluids in simple geometries.