A Force Balance Model for the Size Prediction of Droplets Formed at T-junction with Xanthan Gum Solutions

Microfluidic droplet formation at a T-junction in the jetting regime was studied theoretically and an analytical force balance model was proposed to predict the diameter of droplets. The forces governing droplet production in the jetting regime include the shear, interfacial tension, linear momentum and inertial forces. Experiments were carried with non-Newtonian xanthan gum solutions as the dispersed phase. The model predicted the diameters for both the experimental results and published results in the literature to within ±20%. This result is reasonable considering that no fitting parameters were used, and the reasons for this error are discussed. The magnitudes of the forces controlling droplet formation process are also compared in the paper.