Numerical design and optimization of hydraulic resistance and wall shear stress inside pressure-driven microfluidic networks

Abstract

Microfluidic networks represent the milestone of microfluidic devices. Recent advancements in microfluidic technologies mandate complex designs where both hydraulic resistance and pressure drop across the microfluidic network are minimized, while wall shear stress is precisely mapped throughout the network. In this work, a combination of theoretical and modeling techniques is used to construct a microfluidic network that operates under minimum hydraulic resistance and minimum pressure drop while constraining wall shear stress throughout the network. The results show that in order to minimize the hydraulic resistance and pressure drop throughout the network while maintaining constant wall shear stress throughout the network, geometric and shape conditions related to the compactness and aspect ratio of the parent and daughter branches must be followed. Also, results suggest that while a "local" minimum hydraulic resistance can be achieved for a geometry with an arbitrary aspect ratio, a "global" minimum hydraulic resistance occurs only when the aspect ratio of that geometry is set to unity. Thus, it is concluded that square and equilateral triangular cross-sectional area microfluidic networks have the least resistance compared to all rectangular and isosceles triangular cross-sectional microfluidic networks, respectively. Precise control over wall shear stress through the bifurcations of the microfluidic network is demonstrated in this work. Three multi-generation microfluidic network designs are considered. In these three designs, wall shear stress in the microfluidic network is successfully kept constant, increased in the daughter-branch direction, or decreased in the daughter-branch direction, respectively. For the multi-generation microfluidic network with constant wall shear stress, the design guidelines presented in this work result in identical profiles of wall shear stresses not only within a single generation but also through all the generations of the microfluidic network under investigation. The results obtained in this work are consistent with previously reported data and suitable for a wide range of lab-on-chip applications.

Detachment of ligands from nanoparticle surface under flow and endothelial cell contact: Assessment using microfluidic devices

“…These flow rates were selected to maintain similar flow conditions and shear stresses within the devices that were sufficiently low so as to not cause endothelial cell detachment while also maintaining the lower range limit of physiologically relevant shear stresses associated with diseased vasculature . Due to complex bifurcations, loops, and intersections, the shear stresses at the core of the MNs are expected to drop with a return to inlet level shear stresses upon the reunification of the bifurcated channels into the linear portion leading to the exit port . Microvascular network devices were seeded with endothelial cells and conditioned under constant flow for 5 days before cell viability was tested using live/dead fluorescent probes.…”

“…20,30,31 Due to complex bifurcations, loops, and intersections, the shear stresses at the core of the MNs are expected to drop with a return to inlet level shear stresses upon the reunification of the bifurcated channels into the linear portion leading to the exit port. 32 Flow as well as presence of endothelial cells induced significant detachment of PEG from the nanocrystals ( Figure 4A). Physically adsorbed PEG (CPT 1 PEG) was readily desorbed from the surface as indicated by high supernatant-to-pellet ratio ( Figure 4A).…”

Wall Stresses in Cylinder of Stationary Piped Carriage Using COMSOL Multiphysics

“…The outlet boundary was set as a pressure condition, and its value can be set arbitrarily in the incompressible case. In the compressible structure case, this can affect the stress, thus affecting the deformation of the solid [41]. In this proposal, the reference pressure was set at the outlet of the flow to zero [42,43], and the reflux was suppressed.…”

An optimized PDMS microfluidic device for ultra-fast and high-throughput imaging flow cytometry

“…30 Therefore, decreasing the hydraulic resistance could be a method to achieve our purpose. Many parameters could be optimized, like the length and cross section of channels, 31 and the angles of narrow channels. 32 In OTS microscopy and other imaging systems, chips are always limited to the space between objectives, 17 and very long channels are always designed to avoid interference from inlets and lenses.…”