Microfluidic paper-based analytical devices (μPADs) have garnered significant interest as a promising analytical platform in the past decade. Compared with traditional microfluidics, μPADs present unique advantages, such as easy fabrication using established patterning methods, economical cost, ability to drive and manipulate flow without equipment, and capability of storing reagents for various applications. This Review aims to provide a comprehensive review of the field, highlighting fabrication methods available to date with their respective advantages and drawbacks, device designs and modifications to accommodate different assay needs, detection strategies, and the growing applications of μPADs. Finally, we discuss how the field needs to continue moving forward to realize its full potential.

Australia has had the highest rate of mammal extinctions in the past two centuries when compared to other continents. Frequently cited threats include habitat loss and fragmentation, changed fire regimes and the impact of introduced predators, namely the red fox (Vulpes vulpes) and the feral cat (Felis catus). Recent studies suggest that Australia's top predator, the dingo (Canis dingo), may have a suppressive effect on fox populations but not on cat populations. The landscape of fear hypothesis proposes that habitat used by prey species comprises high to low risk patches for foraging as determined by the presence and ubiquity of predators within the ecosystem. This results in a landscape of risky versus safe areas for prey species. We investigated the influence of habitat and its interaction with predatory mammals on the occupancy of medium‐sized mammals with a focus on threatened macropodid marsupials (the long‐nosed potoroo [Potorous tridactylous] and red‐legged pademelon [Thylogale stigmatica]). We assumed that differential use of habitats would reflect trade‐offs between food and safety. We predicted that medium‐sized mammals would prefer habitats for foraging that reduce the risk of predation but that predators would have a positive relationship with medium‐sized mammals. We variously used data from 298 camera trap sites across nine conservation reserves in subtropical Australia. Both dingoes and feral cats were broadly distributed, whilst the red fox was rare. Long‐nosed potoroos had a strong positive association with dense ground cover, consistent with using habitat complexity to escape predation. Red‐legged pademelons showed a preference for open ground cover, consistent with a reliance on rapid bounding to escape predation. Dingoes preferred areas of open ground cover whereas feral cats showed no specific habitat preference. Dingoes were positively associated with long‐nosed potoroos whilst feral cats were positively associated with red‐legged pademelons. Our study highlights the importance of habitat structure to these threatened mammals and also the need for more detailed study of their interactions with their predators.

A disposable enzyme-linked immunosorbent assay (dELISA) device for ate-home or doctor’s office use was developed to detect SARS-CoV-2 antibodies. Serology testing for SARS-CoV-2 antibodies is currently run using well-plate ELISAs in centralized laboratories. However, the scale of serology testing needed for epidemiological and clinical screening studies will overwhelm existing clinical laboratory resources. Instead, a point-of-need device that can be used at home or in doctor’s offices for COVID-19 serology testing must be developed and is one of four target products prioritized by the World Health Organization. Lateral flow assays are common and easy to use, but lack the sensitivity needed to reliably detect SARS-CoV-2 antibodies in clinical samples. This work describes a disposable ELISA device that is as simple to use as a lateral flow assay, but as sensitive as a well-plate ELISA. The device utilizes capillary-driven flow channels made of transparency films and double-sided adhesive combined with paper pumps to drive flow. The geometry of the channels and storage pads enables automated sequential washing and reagent addition steps with two simple end-user steps. An enzyme label is used to produce a colorimetric signal instead of a nanoparticle label in order to amplify signal and increase sensitivity, while the integrated washing steps decrease false positives and increase reproducibility. Naked-eye detection can be used for qualitative results or a smartphone camera for quantitative analysis. The device can detect antibodies at 2.8 ng/mL from whole blood, which was very close the concentration of detectable target in a well-plate ELISA (1.2 ng/mL). In this study the dELISA system was used to detect SARS-CoV-2 antibodies, but we believe that the device represents a fundamental step forward in point-of-care technology that will enable sensitive detection of many other analytes outside of a centralized laboratory.

A disposable enzyme-linked immunosorbent assay (dELISA) device for ate-home or doctor’s office use was developed to detect SARS-CoV-2 antibodies. Serology testing for SARS-CoV-2 antibodies is currently run using well-plate ELISAs in centralized laboratories. However, the scale of serology testing needed for epidemiological and clinical screening studies will overwhelm existing clinical laboratory resources. Instead, a point-of-need device that can be used at home or in doctor’s offices for COVID-19 serology testing must be developed and is one of four target products prioritized by the World Health Organization. Lateral flow assays are common and easy to use, but lack the sensitivity needed to reliably detect SARS-CoV-2 antibodies in clinical samples. This work describes a disposable ELISA device that is as simple to use as a lateral flow assay, but as sensitive as a well-plate ELISA. The device utilizes capillary-driven flow channels made of transparency films and double-sided adhesive combined with paper pumps to drive flow. The geometry of the channels and storage pads enables automated sequential washing and reagent addition steps with two simple end-user steps. An enzyme label is used to produce a colorimetric signal instead of a nanoparticle label in order to amplify signal and increase sensitivity, while the integrated washing steps decrease false positives and increase reproducibility. Naked-eye detection can be used for qualitative results or a smartphone camera for quantitative analysis. The device can detect antibodies at 2.8 ng/mL from whole blood, which was very close the concentration of detectable target in a well-plate ELISA (1.2 ng/mL). In this study the dELISA system was used to detect SARS-CoV-2 antibodies, but we believe that the device represents a fundamental step forward in point-of-care technology that will enable sensitive detection of many other analytes outside of a centralized laboratory.

A capillary-driven microfluidic sequential flow device, designed for eventual at-home or doctor’s office use, was developed to perform an enzyme-linked immunosorbent assay (ELISA) for serology assays. Serology assays that detect...