Experimental and computational study of microfluidic flow-focusing generation of gelatin methacrylate hydrogel droplets

This work presents the experimental and computational study of droplet generation for hydrogel prepolymer solution in oil using a flow-focusing device. Effects of different parameters on hydrogel droplet generation and droplet sizes in a flow-focusing device were investigated experimentally and computationally. First, three dimensional (3D) computational simulations were conducted to describe the physics of droplet formation in each regime and mechanism of three different regimes: squeezing, dripping, and jetting regime of hydrogel were investigated. Subsequently, the effects of viscosity, inertia force, and surface tension force on droplet generation, and droplet size were studied through these experiments. The experiments were carried out using different concentration of gelatin methacrylate (GelMA) hydrogel (5 wt % and 8 wt %) as the dispersed phase and two different continuous phase liquids (light mineral oil and hexadecane) with various concentrations of surfactant (0 wt %, 3 wt %, and 20 wt %). All experimental data was summarized by capillary number of dispersed phases and the continuous phases to characterize the different regimes of droplet generation and to predict the transition of dripping to a jetting regime for GelMA solution in flow-focusing devices. It is shown that the transition of dripping to a jetting regime for GelMA happens at lower capillary numbers compared to aqueous solutions. Moreover, by increasing the viscous force of continuous phase or decreasing the interfacial force, the size of GelMA droplets was decreased. By controlling these parameters, the droplet sizes can be controlled between 30 lm and 200 lm, which are very suitable for cell encapsulation. VC 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43701.