Microfluidic flows are a powerful tool to drive reactions far from equilibrium and, thus, induce chemical selforganization. Studies of membrane formation in microfluidic devices have been limited to non-redox and purely inorganic reactions. Here, the formation of hybrid membranes at the interface of AgNO3 and 3,3',5,5'-tetramethylbenzidine solutions, which are steadily co-injected into a microfluidic device, is reported. The membrane thickening occurs in both directions and reveals oscillatory dynamics. The hybrid membrane mainly consists of hair-like Ag microstructures, Ag nanowires, and unbranched TMB-TMB2+ microfibers. Branched dendrite-like fibers form on the TMB side when the flow is stopped. These components were characterized with techniques including micro-Raman and energy dispersive X-ray spectroscopy as well as scanning electron microscopy. The effects of initial concentration ratios on the membrane thickening speed and its opaqueness were also studied.
Keywords: dendrites; far from equilibrium; microfluidics; microstructure engineering; relaxation oscillations.
© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.