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

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

Monitoring genetic population biomarkers for wastewater-based epidemiology

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

Frequency dependence of microflows upon acoustic interactions with fluids

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

Experimental and Numerical Studies on a Centrifugal Pump with 2D-Curved Blades in Cavitating Condition

In the presented study a special test-pump with 2D curvature blade geometry in cavitating and non-cavitating conditions was investigated using different experimental techniques and a 3D numerical model of cavitating flows. Experimental and numerical results concerning pump characteristics and performance breakdown were compared at different flow conditions. Appearing types of cavitation and the spatial distribution of vapour structures within the runner were also analysed

Spatially selecting single cell for lysis using light induced electric fields

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

Accurate strain measurements in highly strained Ge microbridges

Ge under high strain is predicted to become a direct bandgap semiconductor. Very large deformations can be introduced using microbridge devices. However, at the microscale, strain values are commonly deduced from Raman spectroscopy using empirical linear models only established up to 1.2% for uniaxial stress. In this work, we calibrate the Raman-strain relation at higher strain using synchrotron based microdiffraction. The Ge microbridges show unprecedented high tensile strain up to 4.9 % corresponding to an unexpected 9.9 cm-1 Raman shift. We demonstrate experimentally and theoretically that the Raman strain relation is not linear and we provide a more accurate expression.Comment: 10 pages, 4 figure

Spontaneous emission control of colloidal nanocrystals using nanoimprinted photonic crystals

The authors report on the fabrication and optical characterizations of two-dimensional photonic crystals fabricated by nanoimprint lithography in a nanocomposite polymer incorporating highly luminescent and red emitting (CdSe)ZnS core-shell colloidal nanocrystals. Photonic crystal structures enhance the light emitted from the quantum sized nanoparticles in the composite layer by slowing the propagation speed of the photons, thus increasing the coupling to the out-of-plane radiative modes. A 200% enhancement of the light collection is achieved compared to an unpatterned sample. (c) 2007 American Institute of Physics. (DOI:10.1063/1.2430625

Surface-directed dewetting of a block copolymer for fabricating highly uniform nanostructured microdroplets and concentric nanorings

Through a combination of nanoimprint lithography and block copolymer self-assembly, a highly regular dewetting process of a symmetric diblock copolymer occurs whereby the hierarchal formation of microdroplets and concentric nanorings emerges. The process is driven by the unique chemical properties and geometrical layout of the underlying patterned silsesquioxane micrometer-sized templates. Given the presence of nonpreferential substrate−polymer interactions, directed dewetting was utilized to produce uniform arrays of microsized droplets of microphase separated polystyrene-block-poly(methyl methylacrylate) (PS-b-PMMA), following thermal annealing at 180 °C. Microdroplets with diameters greater than 400 nm exhibited a hexagonal close-packed arrangement of nanodots on the surface with polydomain ordering. At the droplet periphery, the polydomain ordering was severely disrupted because of a higher in-plane radius of curvature. By reducing the droplet size, the in-plane radius of curvature of the microdroplet becomes significant and the PMMA cylinders adopt parallel structures in this confined geometry. Continuous scaling of the droplet results in the generation of isolated, freestanding, self-aligned, and self-supported oblique nanorings (long axis ∼250−350 nm), which form as interstitial droplets between the larger microdroplets. Optical and magnetic-based nanostructures may benefit from such hierarchal organization and self-supporting/aligned nanoring templates by combining more than one lithography technique with different resolution capabilities