Lattice Boltzmann simulation of droplets manipulation generated in lab-on-chip (LOC) microfluidic T-junction

Abstract

There are various researches about microfluidic systems to appraise influential parameters such as viscosity ratio, volumetric flow rate and Capillary number (Ca). But microfluidic processes are involved in other issues such as valving or making delay in dispersed phase releasing and attaining smooth mixture for chemical reactions. The aim of this paper is investigation of the influential parameters such as Ca number and particularly geometric parameters on droplet releasing, amplifying droplet generation rate in Lab-On-Chip (Laboratory-On-Chip or LOC) microfluidic T-junction using Lattice Boltzmann Method (LBM), applicable in encapsulation, drug delivery, diagnosis of the cancer cells, blood tests and Nucleic Acid (NA) assays. To fulfill this purpose, an asymmetry has been imposed on height of the junction. The results indicated that at a specific difference in height of the junction, the dispersed phase delayed to inter the main duct performing like an active valve instead of utilizing wax to postpone dispersed fluid entrance in the main channel resulting in fluids contamination. Combination of different Ca and asymmetry of the junction amplified droplet generation, desirable in Nucleic Acid assays. Various widths of lateral channel ratio, imposed on the junction illustrated its influence on size and number of droplets. Different entrance velocity ratios were set on the unequal height T-junction indicated its impact on droplet size without any change in other parameters such as volumetric rate of fluids (Q). Change of junction angle caused forming of the slug-like thread providing a slow movement, enhancing contact surface of two phases and consequently smooth mixing of fluids for reaction without any vibration or shaking which is impossible in microfluidic systems.