Droplets Generation using Soluble Polymeric and Surfactant Additives in a Micro-Flow System: An Experimental Approach

Abstract

The effect of polymer on the flow behavior and droplet generation efficiency in a microflow system was investigated.  The effect of the presence of Surfactant molecules on the droplet generation rate and droplets size, and flow behavior in a microfluidic chip was evaluated  The jetting regions phenomena in a microflow system were investigated.In the present work, polymer and surfactant solutions (Xanthan Gum-Cetyltrimethylammonium bromide) were formulated and tested in a micro-flow system (microchannel) carrying octanoic acid as the hydrocarbon phase to determine the droplets formation capabilities of the two different additives. The purpose is to compare the droplet-generated size, shape, and distance between the droplets forming from the individual additives solutions. The jetting phenomenon that happens during droplet generation was also investigated. The solution of the polymer (XG) and surfactant (CTAB) was prepared in 5 different concentrations (50, 100, 150, 200, and 250) ppm and (500, 1000, 1500, 2000, and 2500) ppm, respectively. The continuous and dispersed phases' flow was controlled by controlling the inlet pressure of both phases. Direct-writing lithography was used to fabricate the microchannels using polydimethylsiloxane polymer. The microfluidic chip was connected to an open-loop fluid circulation system, and the produced by polymer and surfactant solutions droplets size was recorded using a high-resolution microscope. The droplet generated using the XG solution was larger, and the distance between droplets was shorter as concentration increased. In contrast, the CTAB solutions showed smaller droplets, and the distance between droplets increased as the concentration increased. The possibility of coalescence of the droplet was also higher as the distance between droplets was shorter. In terms of jetting regime, as the pressure ratio increases, the jet breakup length increases before forming the droplet until, at some limit, the dispersed phase was failed to generate droplets.