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Paper-based microfluidic devices are popular for their ability to automate multistep assays for chemical or biological sensing at a low cost, but the design of paper microfluidic networks has largely relied on experimental trial and error. A few mathematical models of flow through paper microfluidic devices have been developed and have succeeded in explaining experimental flow behavior. However, the reverse engineering problem of designing complex paper networks guided by appropriate mathematical models is largely unsolved. In this article, we demonstrate that a two-dimensional paper network (2DPN) designed to sequentially deliver three fluids to a test zone on the device can be computationally designed and experimentally implemented without experimental trial and error. This was accomplished by three new developments in modeling flow through paper networks: (i) coupling of the Richards equation of flow through porous media to the species transport equation, (ii) modeling flow through assemblies of multiple paper materials (test membrane and wicking pad), and (iii) incorporating limited-volume fluid sources. We demonstrate the application of this model in the optimal design of a paper-based signal-enhanced immunoassay for a malaria protein, PfHRP2. This work lays the foundation for the development of a computational design toolbox to aid in the design of paper microfluidic networks. ©

The abolition of environmental pollutants and production of hydrogen (H2) from water using a heterogeneous photocatalyst is a demanding science of the current scenario to solve the increasing environmental pollution and worldwide energy catastrophe in modern life. To validate this purpose, the design of low-cost and durable semiconductor-based photocatalysts with great light absorption capacity becomes the most challenging issue for researchers. Regarding this, herein the phosphotungstic acid (HPW)-anchored Zr6O4(OH)4(BDC)6 (UiO-66) metal-organic framework (MOF), i.e., HPW@UiO-66, has been prepared by a hydrothermal method and is efficient, stable, and capable of harvesting solar energy toward the degradation of tetracycline hydrochloride (TCH) and H2 production in the presence of a sacrificial donor. The ionic interaction between HPW and UiO-66 plays a key role toward the photostability and charge-transfer mechanism of the composite and is well characterized with X-ray diffraction, UV diffuse-reflectance spectroscopy, Fourier transform infrared, and X-ray photoelectron spectroscopy. A total of 30 wt % HPW@UiO-66 shows a maximum degradation of about 87.24% of a 20 ppm TCH solution in 60 min of solar-light irradiation and about 353.89 μmol/h of H2 production. The conduction- and valence-band potentials are well characterized with Mott-Schottky measurement and a delay charge recombination process through electrochemical impedance spectroscopy. The proposed mediator-free Z-scheme-oriented electron-hole migration route is well supported by photoluminescence, and the scavenger test well explains the better charge-carrier separation and high catalytic performance of the prepared composite. This research will bestow an advantageous blueprint to fabricate novel and challenging photocatalysts toward the photocatalytic treatment of environmental pollutants and H2 evolution.

Paper-based microfluidic devices are popular for their ability to automate multi-step assays for chemical or biological sensing at a low cost, but the design of paper microfluidic networks has largely relied on experimental trial and error. A few mathematical models of flow through paper microfluidic devices have been developed and have succeeded in explaining experimental flow behaviour. However, the reverse engineering problem of designing complex paper networks guided by appropriate mathematical models is largely unsolved. In this article, we demonstrate that a two-dimensional paper network (2DPN) designed to sequentially deliver three fluids to a test zone on the device can be computationally designed and experimentally implemented without trial and error. This was accomplished by three new developments in modelling flow through paper networks: i) coupling of the Richards equation of flow through porous media to the species transport equation, ii) modelling flow through assemblies of multiple paper materials (test membrane and wicking pad), and iii) incorporating limited-volume fluid sources. We demonstrate the application of this model in the optimal design of a paper-based signal-enhanced immunoassay for a malaria protein, PfHRP2. This work lays the foundation for the development of a computational design toolbox to aid in the design of paper microfluidic networks.

A series of Cu salts of heteropoly acid (CuxH3−2xPW12O40) supported MCM-41 catalysts (CuxH3−2xPW12O40/MCM-41) was synthesized by wet impregnation method and thoroughly characterized by using various analytical techniques, viz., X-ray diffraction, UV−vis diffused reflectance spectroscopy (UV−vis DRS), nitrogen adsorption desorption, temperature-programmed reduction (TPR), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FT-IR). From XRD and FT-IR studies, we confirmed that the Keggin structure of heteropoly acid (HPA) is retained in Cu salt of HPA. Heck vinylation was performed to examine the catalytic properties of the catalysts. The 50 wt % CuxH3−2xPW12O40/MCM-41 showed remarkable catalytic performance of phenyl iodide (98% conversion) to cinnamic acid in aqueous medium compared with MCM-41 and other catalytic systems.