Human cells cultivated in a microfluidic system provide an interesting alternative for animal experiments in drug screening. For these tests, a pumpless system based on hydrostatic pressure could be used for drug delivery. The objective of this paper is to provide a method to analyze drug distribution in a gravity-driven microfluidic system to reduce the design cycle of these systems. The approach is based on an analytical model combined with a finite element method (FEM). The paper presents simulation of gravity-driven drug delivery in a polydimethylsiloxane (PDMS)-based microfluidic cell culture system. In the study, a simple but commonly used system including two reservoirs, inlet and outlet, connected through a microchannel, is modeled. In the proposed method, time-dependent working pressure based on hydrostatic and capillary pressures is first approximated analytically. Secondly, using the calculated pressure, a velocity profile of single-phase fluid flow is solved across the system using the FEM. Finally, a distribution of a selected drug compound over the system is simulated and analyzed. Based on the results, the initial geometry is improved for better performance. The paper demonstrates how the modified system provides faster and more uniform drug concentration profile on the cells compared to the initial structure.

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