Diffusion-free valve for preprogrammed immunoassay with capillary microfluidics

By manipulating the geometry and surface chemistry of microfluidic channels,capillary-driven microfluidics can move and stop fluids spontaneously without external instrumentation.Furthermore,complex microfluidic circuits can be preprogrammed by synchronizing the capillary pressures and encoding the surface tensions of microfluidic chips.A key component of these systems is the capillary valve.However,the main concern for these valves is the presence of unwanted diffusion during the valve loading and activation steps that can cause cross-contamination.In this study,we design and validate a novel diffusion-free capillary valve:theπ-valve.This valve consists of a 3D structure and a void area.The void acts as a spacer between two fluids to avoid direct contact.When the valve is triggered,the air trapped within the void is displaced by pneumatic suction induced from the capillary flow downstream without introducing a gas bubble into the circuit.The proposed design eliminates diffusive mixing before valve activation.Numerical simulation is used to study the function and optimize the dimensions of theπ-valve,and 3D printing is used to fabricate either the mould or the microfluidic chip.A comparison with a conventional valve(based on a constrictionexpansion valve)demonstrates that theπ-valve eliminates possible backflow into the valve and reduces the mixing and diffusion during the loading and trigger steps.As a proof-of-concept,this valve is successfully implemented in a capillary-driven circuit for the determination of benzodiazepine,achieving the successive release of 3 solutions in a 3Dprinted microfluidic chip without external instrumentation.The results show a 40%increase in the fluorescence intensity using theπ-valve relative to the conventional value.Overall,theπ-valve prevents cross-contamination,minimizes sample use,and facilitates a sophisticated preprogrammed release of fluids,offering a promising tool for conducting automated immunoassays applicable at point-of-care testing.

Metabolic dysregulation in term infants from SARS-CoV-2-infected mothers

Severe acute respiratory syndrome coronavirus 2(SARSCoV-2)is a novel beta coronavirus that causes coronavirus disease 2019(COVID-19),a severe infectious respiratory disease.In January 2020,the World Health Organization(WHO)declared the outbreak a public health emergency of international concern,and in March 2020.

Influence of carbon-based cathodes on biofilm composition and electrochemical performance in soil microbial fuel cells

Increasing energy demands and environmental pollution concerns press for sustainable and environmentally friendly technologies.Soil microbial fuel cell(SMFC)technology has great potential for carbon-neutral bioenergy generation and self-powered electrochemical bioremediation.In this study,an in-depth assessment on the effect of several carbon-based cathode materials on the electrochemical performance of SMFCs is provided for the first time.An innovative carbon nanofibers electrode doped with Fe(CNFFe)is used as cathode material in membrane-less SMFCs,and the performance of the resulting device is compared with SMFCs implementing either Pt-doped carbon cloth(PtC),carbon cloth,or graphite felt(GF)as the cathode.Electrochemical analyses are integrated with microbial analyses to assess the impact on both electrogenesis and microbial composition of the anodic and cathodic biofilm.The results show that CNFFe and PtC generate very stable performances,with a peak power density(with respect to the cathode geometric area)of 25.5 and 30.4 mW m^(−2),respectively.The best electrochemical performance was obtained with GF,with a peak power density of 87.3 mW m^(−2).Taxonomic profiling of the microbial communities revealed differences between anodic and cathodic communities.The anodes were predominantly enriched with Geobacter and Pseudomonas species,while cathodic communities were dominated by hydrogen-producing and hydrogenotrophic bacteria,indicating H_(2)cycling as a possible electron transfer mechanism.The presence of nitrate-reducing bacteria,combined with the results of cyclic voltammograms,suggests microbial nitrate reduction occurred on GF cathodes.The results of this study can contribute to the development of effective SMFC design strategies for field implementation.

Environmental analysis of innovative sustainable composites with potential use in aviation sector -A life cycle assessment review

The forecast of growing air transport in the upcoming decades faces the challenge of an increasing environmental impact.Aviation industry is working on promising technologies to mitigate this environmental impact.Lightweight design is a strong lever to lower the fuel consumption and,consequently,with it the emissions of aviation.High performance composites are a key technology to help achieve these aims thanks to their favourable combination of mechanical properties and low weight in primary structures.However,mainly synthetic materials such as petrol based carbon fibres and epoxy resins are used nowadays to produce composite in aviation.Renewable materials like bio-based fibres and resin systems offer potential environmental advantages.However,they have not found their way into aviation,yet.The reasons are reduced mechanical properties and,especially for the use of natural fibres,their flammability.Improvements of these shortcomings are under investigation.Therefore the application of bio-based and recycled materials in certain areas of the aircraft could be possible in the future.Good examples for applications are furnishings and secondary structures.The motivation for this paper is to give an overview of potential environmental properties by using such eco-materials in aviation.Life cycle assessment(LCA) is a tool to calculate environmental impacts during all life stages of a product.The main focus is laid on the bio-fibres flax and ramie,recycled carbon fibres and bio-based thermoset resin systems.Furthermore an overview of environmental aspects of existing composite materials used in aviation is given.Generally,a lack of LCA results for the substitution of synthetic materials by bio-based/recycled composite materials in aviation applications has been identified.Therefore,available information from other transport areas,such as automotive,has been summarized.More detailed LCA data for eco-composite materials and technologies to improve their properties is important to understand potential environmental effects in aviation.