Numerical Study on Droplet Formation and Cell Encapsulation Process in a Micro T-junction via Lattice Boltzmann Method

Liquid droplets are widely used as reaction media for the chemical manipulation of cells. The droplet formation and cell encapsulation process involves multiphase flows along with coupled cell membrane-fluid mechanics. In this study, the droplet formation behavior in a T-shaped micro-fluidic device is simulated using two- and three-dimensional lattice Boltzmann method (LBM). With the adoption of pseudo potential model, the LBM can accomplish the accurate tracking of the liquid-liquid or liquid-gas interface automatically. The two-dimensional simulation results agree favorably with experimental results in the aspects of droplet length and the droplet shapes before and after the breakup. For the two-dimensional cell model, the effects of the two important dimensionless parameters, the shear rate and the reduced ratio of bending to elasticity moduli, are investigated systematically. The deformation of the cell in the process of cell encapsulation is found to have close relation with the local flow flied. Surprisingly, it is found that, the cell is still experiencing the force from the surrounding fluid even when the steady transportation of the cell has started after it has been capsulated in a droplet. In the three-dimensional simulations, three regimes of droplet formation are clearly identified as the capillary number increases from 0.002 to 0.056. The previously known four stages of squeezing regime are reproduced. It is noted that the third stage does not exist when the flow moves to the dripping regime. For the jetting regime, the final state of co-flowing will be established after the initial flow transient. It is found that the droplet in the squeezing regime looks like a plug with two semi-spherical cap-like ends, while the droplets in the dripping and jetting regimes resemble a bullet. This difference is discussed based on the relative strength of the shear stress in the flow. A new indicator of the strength of the build-up pressure is proposed. This indicator keeps decreasing from squeezing regime, dripping regime to jetting regime, implying that the build-up pressure plays a less important role as the regime changes from squeezing to jetting.A three-dimensional cell model is developed based on previous studies. In this new model, the factors of in-plane tension, bending stiffness on the surface, and the total volume constraint of the cell are considered. In the simulation of cell encapsulation, the three-dimensional rotation of the cell, including the tank-treading motion of the cell surface, are observed. The movement as well as the deformation of the cell is found to have close relation with the local flow flied.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Chemical and Biomolecular Engineering

Grantor dc:publisher

The Ohio State University

Year dc:date

2013

Author dc:creator

• Yang, Hui

Contributors dc:contributor

• Fan, Liang-Shih

• Chemical Engineering

Statement dc:rights

• unrestricted
• This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.

Language dc:language

English

Repository record dc:identifier

http://rave.ohiolink.edu/etdc/view?acc_num=osu1364836983

OAI identifier oai:identifier

oai:etd.ohiolink.edu:osu1364836983