440 research outputs found

    Capillary-based multiplexed isothermal nucleic acid-based test for sexually transmitted diseases in patients

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    We demonstrate a multiplexed loop mediated isothermal amplification (LAMP) assay for infectious disease diagnostics, where the analytical process flow of target pathogens genomic DNA is performed manually by moving magnetic beads through a series of plugs in a capillary. Heat is provided by a water bath and the results read by the naked eye, enabling applications in low resource settings

    Frequency dependence of microflows upon acoustic interactions with fluids

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    Rayleigh surface acoustic waves (SAWs), generated on piezoelectric substrates, can interact with liquids to generate fast streaming flows. Although studied extensively, mainly phenomenologically, the effect of the SAW frequency on streaming in fluids in constrained volumes is not fully understood, resulting in sub-optimal correlations between models and experimental observations. Using microfluidic structures to reproducibly define the fluid volume, we use recent advances modeling the body force generated by SAWs to develop a deeper understanding of the effect of acoustic frequency on the magnitude of streaming flows. We implement this as a new predictive tool using a finite element model of fluid motion to establish optimized conditions for streaming. The model is corroborated experimentally over a range of different acoustic excitation frequencies enabling us to validate a design tool, linking microfluidic channel dimensions with frequencies and streaming efficiencies. We show that in typical microfluidic chambers, the length and height of the chamber are critical in determining the optimum frequency, with smaller geometries requiring higher frequencies

    Monitoring genetic population biomarkers for wastewater-based epidemiology

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    We report a rapid “sample-to-answer” platform that can be used for the quantitative monitoring of genetic biomarkers within communities through the analysis of wastewater. The assay is based on the loop-mediated isothermal amplification (LAMP) of nucleic acid biomarkers and shows for the first time the ability to rapidly quantify human-specific mitochondrial DNA (mtDNA) from raw untreated wastewater samples. mtDNA provides a model population biomarker associated with carcinogenesis including breast, renal and gastric cancers. To enable a sample-to-answer, field-based technology, we integrated a filter to remove solid impurities and perform DNA extraction and enrichment into a low cost lateral flow-based test. We demonstrated mtDNA detection over seven consecutive days, achieving a limit of detection of 40 copies of human genomic DNA per reaction volume. The assay can be performed at the site of sample collection, with minimal user intervention, yielding results within 45 min and providing a method to monitor public health from wastewater

    Confinement of surface waves at the air-water interface to control aerosol size and dispersity

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    The precise control over the size and dispersity of droplets, produced within aerosols, is of great interest across many manufacturing, food, cosmetic, and medical industries. Amongst these applications, the delivery of new classes of high value drugs to the lungs has recently attracted significant attention from pharmaceutical companies. This is commonly achieved through the mechanical excitation of surface waves at the air liquid interface of a parent liquid volume. Previous studies have established a correlation between the wavelength on the surface of liquid and the final aerosol size. In this work, we show that the droplet size distribution of aerosols can be controlled by constraining the liquid inside micron-sized cavities and coupling surface acoustic waves into different volumes of liquid inside micro-grids. In particular, we show that by reducing the characteristic physical confinement size (i.e., either the initial liquid volume or the cavities’ diameters), higher harmonics of capillary waves are revealed with a consequent reduction of both aerosol mean size and dispersity. In doing so, we provide a new method for the generation and fine control of aerosols’ sizes distribution

    Acoustic Wave Propagation in Microfluidic Application with Hierarchical Finite Element

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    In this paper, we introduce a new computational method for the analysis of fluids subjected to high frequency mechanical forcing. We focus attention on surface acoustic wave droplet microfluidics. In these problems, we distinguish three time scales 1) the fast (μs) time scale of Rayleigh waves on the solid surface, 2) medium (μs-ms) time scale of acoustic wave in the fluid droplet, and 3) slow (ms-s) time scale of capillary wave propagation on the fluid-air surface. Finite element modelling of such problems has been limited in its ability to handle the broad range of timescales. In particular, direct time integration techniques are computationally expensive because of the need to resolve the smallest timescale. Here we solve the Helmholtz equation in the frequency domain, applying hierarchical finite element approximation based on unstructured meshes, where both pressure field and geometry are independently approximated with arbitrary and heterogeneous polynomial order. We demonstrate convergence of the numerical scheme and illustrate model performance using the example of a surface acoustic wave actuation of a droplet, which has applications in microfluidics and microrheology at high frequency

    Green-function method for nonlinear interactions of elastic waves

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    Funding: UK Engineering and Physical Sciences Research Council Fellowship under Grant EP/K027611/1 and in part by the European Research Council advanced investigator award under Grant 340117.In the linear wave propagation regime, an analytical mesh-free Green-function decomposition has been shown as a viable alternative to FDTD and FEM. However, its expansion into nonlinear regimes has remained elusive due to the inherent linear properties of the Green-function approach. This work presents a novel frequency-domain Green function method to describe and model nonlinear wave interactions in isotropic hyperelastic media. As an example of the capabilities of the method, we detail the generation of sum frequency waves when initial quasi-monochromatic waves are emitted in a fluid by finite sources. The method is supported by both numerical and experimental results using immersion ultrasonic techniques.Postprin

    Spatially selecting single cell for lysis using light induced electric fields

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    An optoelectronic tweezing (OET) device, within an integrated microfluidic channel, is used to precisely select single cells for lysis among dense populations. Cells to be lysed are exposed to higher electrical fields than their neighbours by illuminating a photoconductive film underneath them. Using beam spot sizes as low as 2.5 μm, 100% lysis efficiency is reached in <1 min allowing the targeted lysis of cells

    Cycling of rational hybridization chain reaction to enable enzyme-free DNA-based clinical diagnosis

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    In order to combat the growing threat of global infectious diseases, there is the need for rapid diagnostic technologies that are sensitive and that can provide species specific information (as might be needed to direct therapy as resistant strains of microbes emerge). Here, we present a convenient, enzyme-free amplification mechanism for a rational hybridization chain reaction (HCR), which is implemented in a simple format for isothermal amplification and sensing, applied to the DNA-based diagnosis of Hepatitis B virus (HBV) in 54 patients. During the cycled amplification process, DNA monomers self-assemble in an organized and controllable way, only when a specific target HBV sequence is present. This mechanism is confirmed using super-resolution Stochastic Optical Reconstruction Microscopy (STORM). The enabled format is designed in a manner analogous to an enzyme-linked immunosorbent assay (ELISA), generating coloured products with distinct tonality and with a limit of detection of ca. 5 copies/reaction. This routine assay also showed excellent sensitivity (>97%) in clinical samples demonstrating the potential of this convenient, low cost, enzyme-free method for use in low resource settings

    Channel integrated optoelectronic tweezer chip for microfluidic particle manipulation

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    Light patterned electrical fields have been widely used for the manipulation of microparticles, from cells to microscopic electronic components. In this work, we explore a novel electromechanical phenomenon for particle focusing and sorting where the electrical field patterns are shaped by a combination of the light patterned photoconductor and the channel geometry. This effect results from the combination of particle polarisation described by the Clausius–Mossotti relation and the engineering of large electric gradients produced by choosing the channels height to suit the size of the particles being manipulated. The matched geometry increases the distortion of the field created by a combination of the illuminated photoconductor and the particles themselves and hence the non-uniformity of the field they experience. We demonstrate a new channel integration strategy which allows the creation of precisely defined channel structures in the OET device. By defining channels in photoresist sandwiched between upper and lower ITO coated glass substrates we produce robust channels of well controlled height tailored to the particle. Uniquely, the top substrate is attached before photolithographically defining the channels. We demonstrate versatile control using this effect with dynamically reconfigurable light patterns allowing the retention against flow, focusing and sorting of micro particles within the channels. Contrary to traditional designs, this channel integrated device allows patterned micro channels to be used in conjunction with conductive top and bottom electrodes producing optimal conditions for the dielectrophoretic manipulation as demonstrated by the rapid flow (up to 5 mm s−1) in which the particles can be focused

    Lipid topology and linear cationic antimicrobial peptides: a novel mechanistic model

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    The dataset is a dedicated LabVIEW virtual instrument, for the analysis of dye-efflux dynamics. The instrument is capable of automatically extracting the apparent permeability from the leakage of encapsulated fluorescent markers, from within artificial cell systems