Cell transport in microchannels is very important in biological cell labeling, separation and bio-diagnosis technologies. Other applications include drug delivery, DNA sensing, miRNA transport and water purification. In this thesis, mathematical models of cell transport in microchannels are simulated to understand cell motion as cells travel through micro-devices.
The objectives of the modeling are: to characterize particle or biological cell motion in different control systems, including pressure drop, electric field, and magnetic field induced transport, to observe cell transport properties in cell labeling, separation and bio-diagnosis technologies, and to determine the channel surface effect on a particle or cell
motion and distribution near walls.
Assuming a particle or cell is uncharged, the particle/cell transport in a pressure-driven flow is hindered by the size of the cell while both very small cells and very large cells move slowly. Numerical simulations of pressure-driven flow are applied to the cell labeler (cell-antibody
binding enhancement device) design. The improvement of cell-antibody binding
brought by oblique grooves embedded within the cell labeler is proved. Furthermore, the optimum geometry of the oblique grooves and the minimum mixing length are found to provide good cell labeling efficiency in a cell labeler with parallel pattern grooves.
When a cell or particle is subjected to an external field, the effect of the cell or particle on the surrounding fluid is due to forces from both the external fields and surfaces acting on the cell or particle. Dimensional analysis shows that forces from an external electro-magnetic
field and forces from particle-fluid friction are the primary forces that control the motion of a magnetized particle/cell.
Particle transport and cell transport are investigated within electrokinetically-driven flow. The wall effects of electrophoretic motion on both the particle and cell are negligible, unlike in the uncharged case. The electric double layer repulsion and van der Waals attraction dominates the wall-to-particle effect, reaching a minimum at the wall-particle separation at 70nm. These were confirmed by comparing with the experimental data.
The concept of osmotic pressure is investigated in a microscopic setting. A cell keeps ionic equilibrium through its porous semi-permeable membrane. Using force balance analysis, the electric and molecular interaction between membrane and solute particles are found to induces the primary force on solute particles, dragging surrounding fluid away from the membrane and causing a pressure gradient. The microscopic model is compared to the classical expression of osmotic pressure, van’t Hoff’s Law, and is found to be in agreement.