Multiphase flows in porous media are important in many natural and industrial processes. Pore-scale models for multiphase flows have seen rapid development in recent years and are becoming increasingly useful as predictive tools in both academic and industrial applications. However, quantitative comparisons between different pore-scale models, and between these models and experimental data, are lacking. Here, we perform an objective comparison of a variety of state-of-the-art pore-scale models, including lattice Boltzmann, stochastic rotation dynamics, volume-of-fluid, level-set, phase-field, and pore-network models. As the basis for this comparison, we use a dataset from recent microfluidic experiments with precisely controlled pore geometry and wettability conditions, which offers an unprecedented benchmarking opportunity. We compare the results of the 14 participating teams both qualitatively and quantitatively using several standard metrics, such as fractal dimension, finger width, and displacement efficiency. We find that no single method excels across all conditions and that thin films and corner flow present substantial modeling and computational challenges.

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Fluid inertia which has conventionally been neglected in microfluidics has been gaining much attention for particle and cell manipulation because inertia-based methods inherently provide simple, passive, precise and high-throughput characteristics. Particularly, the inertial approach has been applied to blood separation for various biomedical research studies mainly using spiral microchannels. For higher throughput, parallelization is essential; however, it is difficult to realize using spiral channels because of their large two dimensional layouts. In this work, we present a novel inertial platform for continuous sheathless particle and blood cell separation in straight microchannels containing microstructures. Microstructures within straight channels exert secondary flows to manipulate particle positions similar to Dean flow in curved channels but with higher controllability. Through a balance between inertial lift force and microstructure-induced secondary flow, we deterministically position microspheres and cells based on their sizes to be separated downstream. Using our inertial platform, we successfully sorted microparticles and fractionized blood cells with high separation efficiencies, high purities and high throughputs. The inertial separation platform developed here can be operated to process diluted blood with a throughput of 10.8 mL min(-1)via radially arrayed single channels with one inlet and two rings of outlets.

A porous N-doped carbon-encapsulated CoNi alloy nanoparticle composite (CoNi@N−C) was prepared using a bimetallic metal−organic framework composite as the precursor. The optimal prepared Co 1 Ni 1 @N−C material at 800 °C exhibited well-defined porosities, uniform CoNi alloy nanoparticle dispersion, a high doped-N level, and scattered CoNi−N x active sites, therefore affording excellent oxygen catalytic activities toward the reduction and evolution processes of oxygen. The oxygen reduction (ORR) onset potential (E onset ) on Co 1 Ni 1 @N−C was 0.91 V and the halfwave potential (E 1/2 ) was 0.82 V, very close to the parameters recorded on the Pt/C (20 wt Pt%) benchmark. Moreover, it is worth noting that the ORR stability of Co 1 Ni 1 @N−C was prominently higher than that of Pt/C. Under the oxygen evolution reaction condition, Co 1 Ni 1 @N−C generated the maximum current density at the potential of 1.7 V (8.60 mA cm −2 ) and the earliest E onset (1.35 V) among all Co x Ni y @N−C hybrids. The Co 1 Ni 1 @N−C catalyst exhibited the smallest ΔE value, confirming the superior bifunctional activity. The high surface area and porosity, and CoNi−N x active sites on the carbon surface including the proper interactions between the N-doped C shell and CoNi nanoparticles were attributed as the main contributors to the outstanding oxygen electrocatalytic property and good stability.