Microfluidics enhanced synthesis of micellar nanostructures

Abstract

Surfactant molecules can self-assemble into various morphologies under proper combinations of surfactant concentration, temperature, and flow conditions. In equilibrium, micelles can transition from entangled to branched structures with increasing ionic strength and temperature. Under flow conditions, micellar structure transition can follow different trajectories. In the present work, the structural and rheological evolution of both ionic and non-ionic micellar solutions are studied. When both ionic and non-ionic micellar solutions are subjected to strain rates ∼10^3 s−1 and strain ∼10^3, we observe the formation of stable flow-induced structured phases (FISPs), with entangled, branched, and multi-connected micellar bundles, evidenced by electron microscopy (cryo-EM, TEM, and SEM) and small-angle neutron scattering (SANS). The rheological properties of both ionic and non-ionic micellar solutions and their corresponding FISPs are obtained by using one point passive microrheology and two point passive microrheology. The rheological properties variation from the original micellar solutions to their corresponding FISPs is associated with the structural evolution from the precursor to FISPs. The formation of FISPs is correlated with local micellar gradients concentrations, hight stretching in the microposts arrays, entropic fluctuations, flow kinematics, and microspatial confinement. Finally, some potential sensing applications and nanotemplating uses of the FISPs are presented.