1,720,989 research outputs found
Laser-based direct-write technique for enabling newer functionalities in paper-based devices
No full textThe demand for low-cost diagnostic devices that are user-friendly and deliver results rapidly to the patients is a universally accepted goal that has led to extensive development of paper-based microfuidic devices (µPADs). Despite the progress in the field of µPADs, there are still some important requirements yet to be addressed to improve their performance and enable their widespread use as a commercial product. In this thesis, we focus on the use of a laser-based direct-write (LDW) technique for enabling newer functionalities in paper-based devices for improved sensitivity of diagnostic tests as well as the quantitative detection of either a single or multiple analytes. The LDW method we are using for paper patterning is based on the local deposition of a photo-polymer on top of a porous substrate followed by the exposure with a laser light source to create solid polymeric structures. In our first demonstration, we are using the LDW method to create in-line filters on a porous nitrocellulose membrane that are capable of separating particles based on their size. These in-line filters act as barriers to delay the flow of samples and increase the sensitivity for the detection of an analyte. The LDW method is later used to create porous flow-through filters on cellulose paper that again have the ability for the size-exclusive separation of particles. When these flow-through filters are combined with a lateral flow assay they can act as a diagnostic tool for the detection of a single analyte over a wide concentration range. Additionally, the LDW can be extended for the fabrication of platforms that are able to detect multiple analytes within the same device. For that, we report the fabrication of multilayer 3D-µPADs used for the simultaneous detection of three analytes spiked in artificial urine as well as the pH of the tested sample. Finally, we report the use of light-activated materials (hydrogels) on paper-based devices to create optically triggered gates that are able to control the flow of samples, and therefore provide an alternative pathway to increase the sensitivity for the detection of analytes. Adding these newer functionalities to paper-based devices is highly desirable, as this will allow their extensive use as a diagnostic sensor at the point-of-care
Laser direct-write technique for rapid multiplexed detection on lateral-flow devices
No full textPaper-based lateral flow devices (LFD) that allow rapid non-quantitative detection of a single analyte in a fluidic sample, within a time-span of 5-30 minutes are regarded as ideal diagnostic solutions for point-of-care (POC) scenarios, especially for the under-resourced settings of developing countries with remote poorly accessible regions. In recent years, there has been an increasing need for performing multiplexed diagnostics at the POC for rapid and simultaneous detection of multiple analytes within a single sample. Currently, only a few commercial LFDs provide such multiplexing either by laminating together different individual LFDs or alternatively, by multiplexing within a single flow-path. Such devices have critically- inherent drawbacks such as, for the former, increased device dimensions and therefore need for larger sample volumes, and for the latter, an undesired interference between different detection sites, i.e. the influence of each of the previous test-lines on subsequent lines positioned further along the flow-path.Herein, to overcome both these limitations, we propose a novel solution – a multi-path LFD (Fig.1) created via the precise partition of the flow-path of a single LFD using our previously reported, proprietary laser direct-write (LDW) technique. The multiple flow-paths allow individual detection of the different analytes in each of the separated channels. Fig.1a shows the schematic of an example three-channel LFD that can be used for simultaneous detection of three different analytes within the same sample. The appearance of coloured test lines in individual channels indicates the presence of the different analytes. Fig.1b shows the use of this three-channel LFD for multiplexed detection of a biomarker panel comprising C-reactive protein, Serum amyloid A-1 and Procalcitonin, used for the diagnosis of bacterial infections.In conclusion, we demonstrate the use of our LDW technique for the creation of multiple flow-paths within a ‘single’ LFD, which allows multiplexed detection, and thereby a hugely improved detection-efficiency
Laser direct-write of microfluidic flow channels via additive manufacturing for paper-based rapid diagnostics
No full textFabrication of paper-based microfluidic devices using laser direct-writing
No full textPaper-based diagnostic devices have become prevalent in the last decade as low-cost alternatives to conventional point-of-care diagnostic tools. Here, we present the use of a novel laser-based fabrication technique that relies on the principle of laser-induced photo-polymerisation for fabrication of paper-based microfluidic sensors for diagnostic applications
Local deposition assisted laser direct-write technique for fabrication of paper-based microfluidic devices
No full textIn recent years, the requirements for easy-to-use, low-cost and accurate diagnostic solutions have led to rapid progress in the development of in-vitro point-of-care (POC) diagnostic devices, especially lab-on-chip type POC devices. Paper-based micro-analytical devices, proposed by the Whitesides’ group have gained widespread popularity as alternatives to traditional diagnostics. Several methods such as wax printing, UV lithography etc. have already been reported for creating such fluidic devices in paper. In our previous works, we have demonstrated the usefulness and versatility of a laser direct-write (LDW) technique in the patterning of fluidic devices in porous materials for creation of diagnostic devices and have proved its potential as a technique that can be up-scaled for mass-production of paper-based devices at affordable cost. To further improve, optimise and simplify this approach, we propose the inclusion of a local-deposition procedure that involves the deposition of the photopolymer only at desired locations on the paper platform. As in the schematic (Fig.1) describing the local-deposition assisted LDW setup, the photopolymer is first locally deposited onto the paper substrate via a deposition nozzle at designated locations, and a laser beam subsequently illuminates the deposited patterns to induce curing of the photopolymer. The solidified patterns produced through the curing define the fluidic walls that confine and transport the liquids within the porous substrate. In addition, the non-contact nature of the fabrication process renders the platform substrate unaltered and the device free of contaminants. Furthermore, we show the possibility of creating devices with unique advantages such as the creation of surface-relief structures (Fig.2) that help avoid overflow and hence devices that can handle large volumes.We have demonstrated fabrication speeds of >1m/s making the local-deposition assisted LDW process well-suited for rapid and cost-effective roll-to-roll manufacture of paper-based microfluidic devices for a varied set of applications
Capillary-based reverse transcriptase loop-mediated isothermal amplification for cost-effective and rapid point-of-care COVID-19 testing
No full textAs the SARS-CoV-2 pandemic continues to spread, the necessity for rapid, easy diagnostic capabilities could never have been more crucial. With this aim in mind, we have developed a cost-effective and time-saving testing methodology/strategy that implements a sensitive reverse transcriptase loop-mediated amplification (RT-LAMP) assay within narrow, commercially available and cheap, glass capillaries for detection of the SARS-CoV-2 viral RNA. The methodology is compatible with widely used laboratory-based molecular testing protocols and currently available infrastructure. It employs a simple rapid extraction protocol that lyses the virus, releasing sufficient genetic material for amplification. This extracted viral RNA is then amplified using a SARS-CoV-2 RT-LAMP kit, at a constant temperature and the resulting amplified product produces a colour change which can be visually interpreted. This testing protocol, in conjunction with the RT-LAMP assay, has a sensitivity of ∼100 viral copies per reaction of a sample and provides results in a little over 30 min. As the assay is carried out in a water bath, commonly available within most testing laboratories, it eliminates the need for specialised instruments and associated skills. In addition, our testing pathway requires a significantly reduced quantity of reagents per test while providing comparable sensitivity and specificity to the RT-LAMP kit used in this study. While the conventional technique requires 25 μl of reagent, our test only utilises less than half the quantity (10 μl). Thus, with its minimalistic approach, this capillary-based assay could be a promising alternative to the conventional testing, owing to the fact that it can be performed in resource-limited settings, using readily available apparatus, and has the potential of increasing the overall testing capacity, while also reducing the burden on supply chains for mass testing
Semi-quantitative, paper-based detection of the inflammatory biomarkers, C-reactive protein and procalcitonin using laser-patterned multiplex technology
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