Search Results (87)

Slip ring–brush assemblies are widely used in satellite mechanisms to transmit power and signals across rotating interfaces. Under authentic space environments—vacuum, radiation-dominated thermal exchange, and long-duration operation—the coupled effects of mechanical contact dynamics, electrical conduction, intermittent separation, and arcing can accelerate wear and degrade reliability. This paper presents a surface-resolved multiphysics model for multi-track slip rings with staggered brushes. The ring surface is discretized on a circumferential–axial grid and endowed with correlated 3D roughness, enabling interference-based asperity contact. Brush normal dynamics (mass–spring–damper) convert runout and micro-vibration into normal-force ripple and separation events. Electrical conduction is modeled by a parallel admittance network combining pressure-dependent micro-contact conduction and an event-based arc channel activated by separation, opening velocity, and current density with stochastic ignition. A 2D thermal model with ADI integration accounts for Joule/friction heating, radiative cooling, and optional hub conduction. Wear evolves via an Archard-type mechanical term and an arc-energy-driven erosive term. A FAST–MACRO multiscale scheme (20 s FAST, 100 h MACRO with periodic recalibration) enables tractable long-horizon wear prediction while preserving arc statistics. Baseline simulations for a 28 V bus demonstrate rare but nonzero arc activity and predict spatially non-uniform wear at the micrometer scale after 100 h. Full article

Through-plane electronic transport in porous membrane electrode assembly (MEA) electrodes is governed by the three-dimensional (3D) connectivity of the conducting phase. Here, we quantify the role of the spanning-cluster fraction $P_{\infty }$, defined as the fraction of conducting-phase voxels that belong to the $z$-spanning connected component in a finite reconstructed volume, on effective conductivity using scanning electron microscopy (SEM)-informed 3D reconstructions of four archetypal morphologies: a granular catalyst layer (CL), labeled CL1; a fibrous gas diffusion layer (GDL), labeled GDL1; an open-cell foam (OCF); and a micro-fibrous non-woven (MFM), labeled MFM1. Each morphology is reconstructed on a $150\times 150\times 150$ voxel grid, and $z$-spanning connectivity is identified with a 26-neighbor flood-fill algorithm. Steady-state conduction is solved by a finite-volume method (FVM) with an imposed potential difference between the z-faces and no-flux lateral boundaries. Although all samples exhibit through-thickness connectivity, the normalized conductivity ${\sigma }_{\mathrm{e}\mathrm{f}\mathrm{f}}/{\sigma }_{\mathrm{b}\mathrm{u}\mathrm{l}\mathrm{k}}$ varies widely, from $\approx 0.134$ (MFM1) to $\approx 0.706$ (OCF). The corresponding ${(P}_{\infty },{\sigma }_{eff}/{\sigma }_{bulk})$ pairs are $\left(0.996,\approx 0.306\right)$ for CL1, $\left(0.999,\approx 0.303\right)$ for GDL1, $\left(0.997,\approx 0.706\right)$ for OCF, and $\left(0.901,\approx 0.134\right)$ for MFM1. OCF exhibits the highest response due to vertically coherent channels, whereas MFM1 underperforms due to laminated constrictions; CL1 and GDL1 lie in an intermediate regime with nearly isotropic skeletons. Overall, the results show that while a $z$-spanning connected component is required for measurable conduction, the magnitude of ${\sigma }_{\mathrm{e}\mathrm{f}\mathrm{f}}$ is dictated by percolating-skeleton quality (bottlenecks, cross-sectional constrictions, and pathway alignment) rather than phase amount alone. The proposed descriptors therefore enable percolation-aware screening metrics for designing and comparing MEA-relevant GDL and CL microstructures. Full article

This study introduces an innovative microfluidic-based approach for extracting drugs from oral fluids using self-assembled tripeptide hydrogels as sorbents. Peptide microfiber derived from the heterochiral tripeptide ^DLeu-^LPhe-^LPhe was formed in situ within the 14 mm-long microchannel of a two-inlet microfluidic device. The methodology enables the laminar flow-driven mixing of buffer solutions, inducing hydrogel formation at their interface. The resulting fiber exhibited a well-defined morphology and β-sheet structure, confirmed by Raman spectroscopy and Thioflavin T fluorescence. The peptide fibers co-assembled successfully with 5-fluorouracil (5-FU) and naproxen (39.8 ± 1.4 nmol of 5-FU and 27.4 ± 6.6 nmol of naproxen per 112 nmol of peptide used to prepare the fiber), resulting in a molar ratio drug/peptide ratio of approximately 1:3 and 1:4, respectively, demonstrating versatility in drug entrapment. The use of the gel fiber as a sorbent phase was first assessed in buffer, and subsequently, the optimized method was applied to saliva. Adsorption studies under stopped-flow conditions showed a significant drug adsorption capability from buffered solutions by the pre-formed hydrogel (32.8 ± 0.9% of 5-FU and 36.4 ± 3.3% of naproxen per fiber preformed with 112 nmol of peptide), demonstrating their suitability as sorbent material. The extension of the methodology to simulated saliva samples allowed extraction of 36% of 5-FU by the fiber, as determined by ¹⁹F NMR spectroscopy on microcoils, which enabled us to work with the small volume of fluid extracted from the microfluidic device and provided clean spectra and quantitative results. These findings highlight the potential of this tripeptide hydrogel as a sorbent material for therapeutic drug monitoring and toxicological analysis via a simple, non-invasive and rapid approach for drug detection in oral fluids. Full article

von Willebrand factor (vWF) is a large glycoprotein in the circulation system, which senses hydrodynamic force at vascular injuries and then recruits platelets in assembling clots. How vWF mechanosenses shear flow for molecular unfolding is an important topic. Here, a Förster resonance energy transfer (FRET) biosensor was developed to monitor vWF conformation change to hydrodynamic force. The vWF-based biosensor is anchored on the cell surface, in which the A2 domain is flanked with a FRET pair. With 293T cells seeded into microfluidic channels, 2.8 dyn/cm² of shear force (i.e., 28 μN/cm², or 264.1/s in shear rate) induced a remarkable FRET change (~60%) in 30 min. A gradient micro-shear below 2.8 dyn/cm² demonstrated FRET responses positively related to flow magnitudes, with 0.14 dyn/cm² (1.4 μN/cm²) inducing an obvious change (~16%). The FRET increases indicate closer positioning of A2’s two terminals in vWF or the addition of a more parallel orientation of the FRET pair, supported with the high FRET of the A2-only-based biosensor, which probably resulted from flow-induced A2 dissociation from vWF intramolecular binding such as that in A1/A3 domains. Interestingly, gradient flow increases from 2.8 to 28 dyn/cm² led to decreasing FRET changes, suggesting the second-level unfolding in the A2 domain. The LOCK-vWF biosensor with bridged A2 two terminals or an A2-only biosensor could not sense the shear, indicating a structure-flexible A2 and large vWF molecules that are important in the mechanosensation. In conclusion, the developed vWF-based biosensor demonstrated the high mechanosensation of vWF with two-level unfolding to shear force: the dissociation of the A2 domain from vWF intramolecular binding under a micro-shear, and then the unfolding of A2 in vWF under a higher shear; the FRET response to shear force at a very low scale may support the observed clot formation at microvascular wounds. This study provides new insights into the vWF’s mechanosensitive feature for its physiological functions and implicated disorders. Full article

By utilizing polydimethylsiloxane (PDMS), collagen hydrogel, and a cell line for human cerebral microvascular endothelial cells, we produced a 3D microchannel blood–brain barrier (BBB) model under physiological flow. This 3D BBB has a circular-shaped cross-section and a diameter of ~100 μm, which can properly mimic the cerebral microvessel responsible for material exchange between the circulating blood and brain tissue. The permeability of the 3D microchannel BBB to a small molecule (sodium fluorescein with a molecular weight of 376) and that to a large molecule (Dex-70k) are the same as those of rat cerebral microvessels. This 3D BBB model can replicate the effects of a plasma protein, orosomucoid, a cytokine, vascular endothelial growth factor (VEGF), and an enzyme, heparinase III, on either rat cerebral or mesenteric microvessesels in terms of permeability and the modulation of glycocalyx (heparan sulfate). It can also replicate the adhesion of a breast cancer cell, MDA-MB-231, in rat mesenteric microvessels under no treatment or treatments with VEGF, orosomucoid, and heparinase III. Because of difficulties in accessing human cerebral microvessels, this inexpensive and easy to assemble 3D human BBB model can be applied to investigate BBB-modulating mechanisms in health and in disease and to develop therapeutic interventions targeting tumor metastasis to the brain. Full article

Narrow Fluvial Sand Bodies are primarily developed along the river center, with horizontal wells for injection and production in some Bohai waterflooded oilfields. This results in a rapid increase in water cut due to a single injection–production direction. Over time, dominant water breakthrough channels form between wells, and the remaining oil moves to deeper regions, which makes conventional profile control measures less effective. We developed a quantitative method based on integrated dynamic and static big data to identify these breakthrough channels and measure the flow intensity between injection and production wells. To address deep remaining oil mobilization, we performed micro-analysis and physical simulations with heterogeneous core models, which led to the development of a deep profile control system using emulsion polymer gel and self-assembling particle flooding. Experiments show that the combined technology can reduce oil saturation in low-permeability layers to 45.3% and improve recovery by 30.2% compared to water flooding. Field trials proved to be completely effective, with a cumulative oil increase of over 23,200 cubic meters and a 12% reduction in water cut per well. This deep profile control technology offers significant water cut reduction and enhanced oil recovery. It can provide technical support for efficient water control and profile management in similar reservoirs. Full article

In this study, we present a novel 3D perfused skin-on-a-chip model fabricated using micro-precision 3D printing, which offers a streamlined and reproducible approach for incorporating perfusion. Perfused skin models are well-regarded for their advantages, such as improved nutrient supply, enhanced barrier function, and prolonged tissue viability. However, current models often require complex setups, such as self-assembled endothelial cells or sacrificial rods, which are prone to variability and time-consuming. Our model uses projection micro-stereolithography 3D printing to create precise microcapillary-like channels using a biocompatible resin, overcoming the drug-absorbing properties of PDMS. A customized chip holder allows for the simultaneous culture of six perfused chips, enabling high-throughput testing. The engineered skin-on-a-chip features distinct dermis and epidermis layers, confirmed via H&E staining and immunostaining. To evaluate drug screening capabilities, inflammation was induced using TNF-α and treated with dexamethasone, with cytokine levels compared to 2D cultures and human skin biopsies. Our 3D model exhibited drug response trends similar to human skin, while showing reduced cytotoxicity over time compared to biopsies. This perfused skin-on-a-chip provides a reliable, physiologically relevant alternative for drug and cosmetics screening, simplifying perfusion setup while preserving key benefits. Full article

How to effectively plug the multi-scale fractured water channeling has always been the key to achieving efficient water flooding of fractured low-permeability oil reservoirs. In this paper, a new type of supramolecular–polymer composite gel is developed, which is suitable for plugging multi-scale fractured water channeling. The supramolecular–polymer composite gel is composed of a polymer (such as polyacrylamide), cross-linking agent (such as polyethyleneimine), supramolecular gel factor (such as cyclodextrin) and polarity regulator (such as ethyl alcohol). The mass fraction of polyacrylamide, polyethyleneimine, cyclodextrin and ethyl alcohol are 0.15%, 0.2%, 1% and 0.2%, respectively. At the initial state, the viscosity of the composite gelant system is less than 20 mPa·s. It has good injection performance in micro-scale fractures and can enter the deep part of a fractured reservoir. At 40 °C, the composite gelant system can form a gel with a double network structure after gelation. One of the networks is formed by the covalent interaction between polyacrylamide and polyethyleneimine, the other network is formed by the self-assembly of cyclodextrins under the action of the ethyl alcohol. The comprehensive performance of the composite gel is greatly improved. The strength of the composite gel is >5 × 10⁴ mPa·s, and it has good plugging strength in large-scale fractures. The composite gel can be used as a conformance control agent for fractured low-permeability oilfields. Full article

Inflammatory bowel diseases (IBDs) involve chronic inflammation of the gastrointestinal tract, where effector CD4⁺ T-cells play a central role. Thereby, the recruitment of T-cells into the colonic mucosa represents a key process in IBD. We recently found that CCR9 and DRD5 might form a heteromeric complex on the T-cell surface. The increase in CCL25 production and the reduction in dopamine levels associated with colonic inflammation represent a dual signal stimulating the CCR9:DRD5 heteromer, which promotes the recruitment of CD4⁺ T-cells into the colonic lamina propria. Here, we aimed to analyse the molecular requirements involved in the heteromer assembly as well as to determine the underlying cellular mechanisms involved in the colonic tropism given by the stimulation of the CCR9:DRD5 complex. The results show that dual stimulation of the CCR9:DRD5 heteromer potentiates the phosphorylation of the myosin light chain 2 (MLC2) and the migration speed in confined microchannels. Accordingly, disrupting the CCR9:DRD5 assembly induced a sharp reduction in the pMLC2 in vitro, decreased the migratory speed in confined microchannels, and dampened the recruitment of CD4⁺ T-cells into the inflamed colonic mucosa. Furthermore, in silico analysis confirmed that the interface of interaction of CCR9:DRD5 is formed by the transmembrane segments 5 and 6 from each protomer. Our findings demonstrated that the CCR9:DRD5 heteromeric complex plays a fundamental role in the migration of CD4⁺ T-cells into the colonic mucosa upon inflammation. Thereby, the present study encourages the design of strategies for disassembling the formation of the CCR9:DRD5 as a therapeutic opportunity to treat IBD. Full article

Additive manufacturing (AM) excels in engineering intricate shapes, pioneering functional components, and lightweight structures. Nevertheless, components fabricated through AM often manifest elevated residual stresses and a myriad of thermally induced micro-instabilities, including cracking, incomplete fusion, crazing, porosity, spheroidization, and inclusions. In response, this study proposed a sophisticated multi-sensing inspection system specifically tailored for the inspection of thermally induced micro-instabilities at the micro–nano scale. Simulation results substantiate that the modulation transfer function (MTF) values for each field of view in both visible and infrared optical channels surpass the benchmark of 0.3, ensuring imaging fidelity conducive to meticulous examination. Furthermore, the innovative system can discern and accurately capture data pertaining to thermally induced micro-instabilities across visible and infrared spectra, seamlessly integrating this information into a backend image processing system within operational parameters of a 380–450 mm distance and a 20–70 °C temperature range. Notably, the system’s design is harmoniously aligned with the requisites of processing and assembly, heralding a significant advancement in bolstering the inspection effect of thermally induced micro-instabilities for the AM component. Full article

In situ electroporation, a non-invasive technique for enhancing the permeability of cell membranes, has emerged as a powerful tool for intracellular delivery and manipulation. This method allows for the precise introduction of therapeutic agents, such as nucleic acids, drugs, and proteins, directly into target cells within their native tissue environment. Herein, we introduce an innovative electroporation strategy that employs a Janus particle (JP)-based microelectrode to generate a localized and controllable electric field within a microfluidic chip. The microfluidic device is engineered with an indium tin oxide (ITO)-sandwiched microchannel, where the electric field is applied, and suspended JP microelectrodes that induce a stronger localized electric field. The corresponding simulation model is developed to better understand the dynamic electroporation process. Numerical simulations for both single-cell and chain-assembled cell electroporation have been successfully conducted. The effects of various parameters, including pulse voltage, duration medium conductivity, and radius of Janus microelectrode, on cell membrane permeabilization are systematically investigated. Our findings indicate that the enhanced electric intensity near the poles of the JP microelectrode significantly contributes to the electroporation process. In addition, the distribution for both transmembrane voltage and the resultant nanopores can be altered by conveniently adjusting the relative position of the JP microelectrode, demonstrating a selective and in situ electroporation technique for spatial control over the delivery area. Moreover, the obtained differences in the distribution of electroporation between chain cells can offer insightful directives for the electroporation of tissues or cell populations, enabling the precise and targeted modulation of specific cell populations. As a proof of concept, this work can provide a robust alternative technique for the study of complex and personalized cellular processes. Full article

This study presents a novel method for manufacturing microfluidic paper–fabric hybrid analytical devices (μPFADs), which play a vital role in conducting diagnostic tests at the point of care (POC), especially in resource-limited environments. By circumventing the need for complex machinery or highly skilled operators, our method presents a practical solution for scaling up these POC devices. The approach involves the utilization of a folded paper structure featuring a specific pattern like a circular well or liner microchannel on either side of the fold as a mirror image, followed by inserting a piece of fabric in between the paper fold, thereby creating a sandwich-like structure. Subsequently, a PDMS (polydimethylsiloxane) elastomer with base and curing agents in a 10:1 ratio would be coated over the entire top paper and allowed to settle, enabling the penetration of PDMS down to the bottom paper through the sandwiched fabric. When sufficient PDMS penetration is achieved through visual changes on the back side of the paper, the sandwiched assembly is heated for polymerization of the PDMS. An embedded fabric-based POC device is obtained within the paper whose structure is defined by the designs on the folded paper itself. This micro paper–fabric hybrid analytical device (μPFAD) offers several noteworthy advantages as it boasts rapid fabrication times and is cost-effective, without the need for any printing machines, thereby further enhancing its suitability for no- or low-resource environments. Experimental studies with these μPFADs were conducted for the colorimetric detection of iodine, whose deficiency is a leading cause of thyroid disorders, particularly hypothyroidism. Here, starch acts as the chromogenic agent, which forms a blue-colored complex that shifts the color from purple to deep blue–black with increasing iodine concentration. The initial experimental results reveal contrasting color changes for varying levels of iodine using the proposed μPFADs, which would be useful for the early diagnosis and management of thyroid disorders. Full article

Real-time monitoring of physiological indicators inside the body is pivotal for contemporary diagnostics and treatments. Implantable electrodes can not only track specific biomarkers but also facilitate therapeutic interventions. By modifying biometric components, implantable electrodes enable in situ metabolite detection in living tissues, notably beneficial in invasive glucose monitoring, which effectively alleviates the self-blood-glucose-managing burden for patients. However, the development of implantable electrochemical electrodes, especially multi-channel sensing devices, still faces challenges: (1) The complexity of direct preparation hinders functionalized or multi-parameter sensing on a small scale. (2) The fine structure of individual electrodes results in low spatial resolution for sensor functionalization. (3) There is limited conductivity due to simple device structures and weakly conductive electrode materials (such as silicon or polymers). To address these challenges, we developed multiple-channel electrochemical microneedle electrode arrays (MCEMEAs) via a separated functionalization and assembly process. Two-dimensional microneedle (2dMN)-based and one-dimensional microneedle (1dMN)-based electrodes were prepared by laser patterning, which were then modified as sensing electrodes by electrochemical deposition and glucose oxidase decoration to achieve separated functionalization and reduce mutual interference. The electrodes were then assembled into 2dMN- and 1dMN-based multi-channel electrochemical arrays (MCEAs), respectively, to avoid damaging functionalized coatings. In vitro and in vivo results demonstrated that the as-prepared MCEAs exhibit excellent transdermal capability, detection sensitivity, selectivity, and reproducibility, which was capable of real-time, in situ glucose concentration monitoring. Full article

The advancement of both porous materials and nanomaterials has brought about porous nanomaterials. These new materials present advantages both due to their porosity and nano-size: small size apt for micro/nano device integration or in vivo transport, large surface area for guest/target molecule adsorption and interaction, porous channels providing accessibility to active/surface sites, and exposed reactive surface/active sites induced by uncoordinated bonds. These properties prove useful for the development of different porous composition types (metal oxides, silica, zeolites, amorphous oxides, nanoarrays, precious metals, non-precious metals, MOFs, carbon nanostructures, MXenes, and others) through different synthetic procedures—templating, colloidal synthesis, hydrothermal approach, sol-gel route, self-assembly, dealloying, galvanostatic replacement, and so—for different applications, such as catalysis (water-splitting, etc.), biosensing, energy storage (batteries, supercapacitors), actuators, SERS, and bio applications. Here, these are presented according to different material types showing the evolution of the structure design and development towards the formation of hierarchical porous structures, emphasizing that the formation of porous nanostructures came about out of the desire and need to form hierarchical porous nanostructures. Common trends observed across these different composition types include similar (aforementioned) applications and the use of porous nanomaterials as templates/precursors to create novel ones. Towards the end, a discussion on the link between technological advancements and the development of porous nanomaterials paves the way to present future perspectives on these nanomaterials and their hierarchical porous architectures. Together with a summary, these are given in the conclusion. Full article

This study focuses on advancing sweat management in clothing using low-current operating textile electroosmotic pumps, which could be beneficial for microenvironments with restricted ventilation, such as the one between the skin and protective wear. These systems, employing silver–copper fabric electrodes, a polycarbonate membrane with microchannels, and an adhesive web, enabled directed liquid transport. The critical role of the adhesive layer preparation is emphasized, often overlooked in previous research. Various adhesive perforations were tested for their impact on the flow under current action, both with and against gravity. Specific adhesive application techniques are proposed, found to significantly influence the flow rate and textile assembly cohesion. The custom setup yielded flow rates of up to 8.8 ± 0.08 mg min⁻¹ cm⁻², suitable for diverse human sweat rates. Optimization hinges on the delicate balance between binding and the active surface areas of the adhesive. Full article