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Paper-based biosensor is one of the most commonly used platforms for point-of-care testing (POCT). Among these platforms, microfluidic paper-based analytical devices (μPADs) have the most versatile designs due to the different hydrophobic barrier patterns and layers of the devices. In addition, μPADs can also be used in combination with other biosensor platforms to improve the performance of the device. Simple and convenient methods for fabricating low-cost and design-adjustable hydrophobic barriers on paper are one of the most challenging aspects for creating μPADs. This work demonstrated a simple technique for using the common polylactic acid (PLA) filament and wax filament to create hydrophobic barriers on paper for μPADs using a commercialized 3D printer. As a proof of concept, the papers with 3D printed PLA barrier were used in combination with a fluidic chip in a prototype biosensor, in which the barrier paper housed four cell-free reactions and the fluidic chip achieved sample delivery to the reactions in the device. Our designed prototype was capable of discriminating dengue virus serotypes based on small nucleotide sequence differences. The proposed combination of 3D-printed barrier paper and fluidic chip provides a versatile platform for rapid prototyping of POCT with possible compatibility with various detection systems.

Membrane emulsification is a promising new technique that can be deployed as a scalable modular conduit for the consistent and continuous production of single and complex emulsions. This work reports on the development of a manufacturing platform based on membrane emulsification for the first time for microcapsule-based self-healing cementitious materials. The feasibility of single and double emulsion production with wall formation as a secondary step through UV radical polymerisation was explored using a discrete membrane emulsification dispersion cell. The operational parameters (pressure, dispersed phase flux, temperature, shear rate) were established for the specific phase characteristics (viscosity, density, interfacial tension) to achieve control of emulsion droplets and maintain a high encapsulation of core content (high payload). Microcapsules with sodium silicate core and an average diameter of ∼130 μm were produced. Microcapsules were shown to achieve high payload (∼89%). Moreover their thermal stability was characterised and their release performance in the cementitious matrix established. The results demonstrated the capability of membrane emulsification to produce microcapsules with an aqueous core for use in self-healing of cementitious materials.

Exposure levels to staff in interventional radiology (IR) may be significant and appropriate assessment of radiation doses is needed. Issues regarding measurements using physical dosemeters in the clinical environment still exist. The objective of this work was to explore the prerequisites for assessing staff radiation dose, based on simulations only. Personal dose equivalent, Hp(10), was assessed using simulations based on Monte Carlo methods. The position of the operator was defined using a 3D motion tracking system. X-ray system exposure parameters were extracted from the x-ray equipment. The methodology was investigated and the simulations compared to measurements during IR procedures. The results indicate that the differences between simulated and measured staff radiation doses, in terms of the personal dose equivalent quantity Hp(10), are in the order of 30–70 %. The results are promising but some issues remain to be solved, e.g. an automated tracking of movable parts such as the ceiling-mounted protection shield.

This article describes the device design and fabrication of two different configurations (flow-through and stopped-flow) of a sequential fluid delivery platform on a microfluidic paper-based device. The developed device is capable of storing and transporting reagents sequentially to the detection channel without the need for external power. The device comprises two components: an origami folding paper (oPAD) and a movable reagent-stored pad (rPAD). This 3D capillary-driven device eliminates the undesirable procedure of multiple-step reagent manipulation in a complex assay. To demonstrate the scope of this approach, the device is used for electrochemical detection of biological species. Using a flow-through configuration, a self-calibration plot plus real sample analysis using a single buffer introduction are established for ascorbic acid detection. We further broaden the effectiveness of the device to a complex assay using a stopped-flow configuration. Unlike other electrochemical paper-based sensors in which the user is required to cut off the device inlet or rest for the whole channel saturation before measurement, herein a stopped-flow device is carefully designed to exclude the disturbance from the convective mass transport. As a proof of concept, multiple procedures for electrode modification and voltammetric determination of serotonin are illustrated. In addition, the research includes an impedimetric label-free immunosensor for α-fetoprotein using the modified stopped-flow device. The beneficial advantages of simplicity, low sample volume (1 μL), and ability to perform a complex assay qualify this innovative device for use with diverse applications.

Aminoglycosides are widely used antibiotics that bind to the bacterial 30S ribosomal subunit to inhibit translation. Owing to their adverse side effects and narrow therapeutic index, monitoring blood levels of aminoglycosides is important to maximize their effectiveness and minimize their toxicity. Current monitoring techniques require a well-equipped diagnostic laboratory. The present study aimed to present a proof-of-concept for a simple, low-cost biochemical assay utilizing a paper platform for the detection of serum/whole blood aminoglycosides. A paper-based bioassay chip for the assay was developed by spotting and freeze-drying cell-free transcription/translation reaction machinery for a luminescent reporter protein (NanoLuc) within an array of wax circles printed on filter paper. The paper-based chip could be used to quantify serum/whole blood aminoglycosides within clinically relevant concentrations in 30–60 min by spotting minimal volumes of samples, followed by the NanoLuc substrate, in the wax circles and detecting the associated changes in luminescence signals, using a simple digital camera. Furthermore, a one-pot assay in which cell-free transcription/translation reaction machinery and NanoLuc substrate are mixed in advance and embedded in paper could be used to detect an aminoglycoside in serum. Overall, our paper-based bioassay can potentially provide a basic platform for the simple and low-cost therapeutic monitoring of aminoglycosides, especially in resource-limited regions.

Currently, the Lateral flow Immunoassays (LFIAs) are not able to perform complex multi-step immunodetection tests because of their inability to introduce multiple reagents in a controlled manner to the detection area autonomously. In this research, a point-of-care (POC) paper-based lateral flow immunosensor was developed incorporating a novel microfluidic valve technology. Layers of paper and tape were used to create a three-dimensional structure to form the fluidic network. Unlike the existing LFIAs, multiple directional valves are embedded in the test strip layers to control the order and the timing of mixing for the sample and multiple reagents. In this paper, we report a four-valve device which autonomously directs three different fluids to flow sequentially over the detection area. As proof of concept, a three-step alkaline phosphatase based Enzyme-Linked ImmunoSorbent Assay (ELISA) protocol with Rabbit IgG as the model analyte was conducted to prove the suitability of the device for immunoassays. The detection limit of about 4.8 fm was obtained.