The objective of this study was to create a microfluidic model of complex porous media for studying single and multiphase flows. Most experimental porous media models consist of periodic geometries that lend themselves to comparison with well-developed theoretical predictions. However, many real porous media such as geological formations and biological tissues contain a degree of randomness and complexity at certain length scales that is not adequately represented in periodic geometries. To design an experimental tool to study these complex geometries, we created microfluidic models of random homogeneous and heterogeneous networks based on Voronoi tessellations. These networks consisted of approximately 600 grains separated by a highly connected network of channels with an overall porosity of 0.11-0.20. We found that introducing heterogeneities in the form of large cavities within the network changed the permeability in a way that cannot be predicted by the classical porosity-permeability relationship known as the Kozeny equation. The values of permeability found in experiments were in excellent agreement with those calculated from three-dimensional lattice Boltzmann simulations. In two-phase flow experiments of oil displacement with water we found that the wettability of channel walls determined the pattern of water invasion, while the network topology determined the residual oil saturation. The presence of cavities increased the microscopic sweeping efficiency in water-oil displacement. These results suggest that complex network topologies lead to fluid flow behavior that is difficult to predict based solely on porosity. The novelty of this approach is a unique geometry generation algorithm coupled with microfabrication techniques to produce pore scale models of stochastic homogeneous and heterogeneous porous media. The ability to perform and visualize multiphase flow experiments within these geometries will be useful in measuring the mechanism(s) of displacement within micro- and nanoscale pores.
The high blood volume requirements and low throughput of conventional flow assays for measuring platelet function are unsuitable for drug screening and clinical applications. In this study, we describe a microfluidic flow assay that uses 50 μL of whole blood to measure platelet function on ~300 micropatterned spots of collagen over a range of physiologic shear rates (50–920 s−1). Patterning of collagen thin films (CTF) was achieved using a novel hydrated microcontact stamping method. CTF spots of 20, 50, and 100 μm were defined on glass substrates and consisted of a dense mat of nanoscale collagen fibers (3.74 ± 0.75 nm). We found that a spot size of greater than 20 μm was necessary to support platelet adhesion under flow, suggesting a threshold injury is necessary for stable platelet adhesion. Integrating 50 μm CTF microspots into a multishear microfluidic device yielded a high content assay from which we extracted platelet accumulation metrics (lag time, growth rate, total accumulation) on the spots using Hoffman modulation contrast microscopy. This method has potential broad application in identifying platelet function defects and screening, monitoring and dosing antiplatelet agents.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.