Simultaneous pressure and electro-osmosis driven flow in charged porous media: Pore-scale effects on mixing and dispersion

Electrokinetics of Erosive Seepage through Deformable Porous Media

Channelization and branching patterns frequently appear in porous structures as a result of fluid-flow-mediated erosion, which causes spatiotemporal changes in the medium. However, most studies on electrokinetic effects in porous media focus on the overall impact of the electric field on electrical double-layer formation in micropores and its influence on ionic transport, without addressing the spatiotemporal erosive characteristics and resulting porosity distribution. In this study, we explore the interplay between flow-induced shear stress and an external electric field on the dynamic evolution of porosity in deformable porous media using semi-analytical modeling. Our numerical simulations accurately predict the differences in porosity and erosive development when the electric field aligns with or opposes the flow, highlighting the importance of the direction of the external stimulus and not just its magnitude. Our findings establish a foundation for electric-field-mediated control of porous media properties and explain electrokinetic transport by considering dynamic porosity variations as a result of erosive deformation, an aspect previously unaddressed.

Pumpless three-dimensional photo paper-based microfluidic analytical device for automatic detection of thioredoxin-1 using enzyme-linked immunosorbent assay

Microfluidic-based biosensors have been developed for their precise automatic reaction control. However, these biosensors require external devices that are difficult to transport and use. To overcome this disadvantage, our group made an easy-to-use, cheap, and light pumpless three-dimensional photo paper-based microfluidic analytical device (3D-μPAD; weight: 1.5 g). Unlike conventional paper-based microfluidic analytical devices, the 3D-μPAD can be used to control fluid flow in a 3D manner, thus allowing sophisticated multi-step reaction control. This device can control fluid flow speed and direction accurately using only the capillary-driven flow without an external device like a pump. The flow speed is controlled by the width of the microfluidic channel and its surface property. In addition, fluid speed control and 3D-bridge structure enable the control of fluid flow direction. Using these methods, multi-step enzyme-linked immunosorbent assay (ELISA) can be done automatically in sequence by injecting solutions (sample, washing, and enzyme's substrate) at the same time in the 3D-μPAD. All the steps can be performed in 14 min, and data can be analyzed immediately. To test this device, thioredoxin-1 (Trx-1), a biomarker of breast cancer, is used as the target. In the 3D-μPAD, it can detect 0-200 ng/mL of Trx-1, and the prepared 3D-μPAD Trx-1 sensor displays excellent selectivity. Moreover, by analyzing the concentration of Trx-1 in real patients and healthy individuals' blood serum samples using the 3D-μPAD, and comparing results to ELISA, it can be confirmed that the 3D-μPAD is a good tool for cancer diagnosis.

Electrodialytic treatment of secondary mining resources for raw materials extraction: Reactor design assessment

The sustainability of mining activities is compromised due to the high amounts of mining residues generated that have to be disposed of, often in open dams, that may cause environmental deterioration, e.g. release of toxic elements to water supplies. These residues are, however, secondary resources of raw materials. In the case of Panasqueira mine, they even are a source of tungsten, considered a critical raw material. The present work aims to assess the electrodialytic process efficiency for raw materials extraction from Panasqueira mine residues. Experiments were performed with 2 and 3-compartment electrodialytic reactors, applying current intensities between 50 and 100 mA, from 4 to 14 days, and sample suspensions enhanced with NaCl or effluent. Additionally, control experiments with no current application were carried out. The results showed that a 3-compartment reactor operating at 100 mA, with NaCl as supporting electrolyte, presented the highest extraction of copper (13%), tin (10%), tungsten (13%) and arsenic (63%).