Irreversible Flow-Induced Structure Transition in Cylindrical Micelle Solutions

It is well known that translucent solutions containing cylindrical surfactant micelles can form flow-induced structures (FISs). To date all reported FIS transitions are reversible, i.e., the gel disintegrates after flow stoppage. We show that in microfluidic devices that allow for the generation of extension rates greater than those realized in conventional rheometers, irreversible FIS transitions can occur [1]. Specifically, at the threshold flow rate for the phase transition, the time scale of flow deformation is comparable to the angular rotation time of the micelle rods. Cryo-TEM analysis of the gel reveals a partially aligned micelle network. Mechanisms and potential applications of the phase transition will be discussed. 1. Vasudevan et al. Nature Materials, 9, 436-441 (2010)