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Immunoagglutination assay is a promising approach for the detection of waterborne analytes like virus, cells, proteins with its advantages such as a smaller amount of reagents and easier operation. This paper presents a microfluidic agglutination assay on which all the assay processes including analyte capture, agglutination, and detection are performed. The chip integrates an on-chip pump for sample loading, a dynamic magnetic bead (MB) clump for analyte capture and agglutination, and a sheath-less flow cytometry for particle detection, sizing, and counting. The chip is tested with streptavidin-coated MBs and biotinylated bovine serum albumin as a model assay, which realizes a limit of detection (LOD) of 1 pM. Then, an antigen/antibody assay using rabbit IgG and goat anti-rabbit IgG coated MBs is tested and a LOD of 5.5 pM is achieved. At last, human ferritin in 10% fetal bovine serum is tested with Ab-functionalized MBs and the detection achieves a LOD of 8.5 pM. The whole procedure takes only 10 min in total. [ABSTRACT FROM AUTHOR]

Here, an integrated microfluidic electrostatic sampler (IMES) was designed and evaluated, consisting of a unipolar charging chamber, a half cylinder precipitation electrode and a collection chip for automated air sample delivery. The collection chip includes a half-open microchannel covered with a hydrophobic mesh and a peristaltic micropump. Airborne particles were first charged in the charging chamber and then precipitated into the half-open microchannel by the electrostatic field. After sampling, the integrated micropump automatically delivered the collection liquid through the half-open microchannel to the liquid outlet, washing away those deposited particles into collection reservoir. The maximum allowable velocity in the half-open microchannel was higher than 200 mm/s which is well above the normal operating speed of sample delivery, thus water transportation was quite stable in use. The collection efficiencies of airborne particles and bio-particles were investigated for the sampler. The tested maximum sampling flow rate was 13.2 L/min and the corresponding maximum effective collection efficiency was about 40% for particles smaller than 5 μm at charging voltage of −1.8 kV and collecting voltage of −7 kV. The preliminary experiments showed that the collection efficiencies of bio-particles were about 16% with aerosolized Bacillus subtilis . The lower collection efficiency of bio-particles was partially due to the particle loss on the hydrophobic mesh. Taking into consideration its compact size and integrated function of charging and automatic liquid sample delivery, the IMES is a bioaerosol sampling system ready for integration with subsequent automated detection equipment. [ABSTRACT FROM AUTHOR]

Microfiltration is a compelling method to separate particles based on their distinct size and deformability. However, this approach is prone to clogging after processing a certain number of particles and forming bubbles in the separation procedure, which often leads to malfunctioning of devices. In this work, we report a bubble-free and clogging-free microfluidic particle separation platform with high throughput. The platform features an integrated bidirectional micropump, a hydrophilic microporous filtration membrane and a hydrophobic porous degassing membrane. The bidirectional micropump enables the fluid to flow back and forth repeatedly, which flushes the filtration membrane and clears the filtration micropores for further filtration, and to flow forward to implement multi-filtration. The hydrophobic porous membrane on top of the separation channel removes air bubbles forming in the separation channel, improving the separation efficiency and operational reliability. The microbead mixture and undiluted whole blood were separated using the microfluidic chip. After 5 cycles of reverse flushing and forward re-filtration, a 2857-fold enrichment ratio and an 89.8% recovery rate of 10 μm microbeads were achieved for microbead separation with 99.9% removal efficiency of 2 μm microbeads. After 8 cycles, white blood cells were effectively separated from whole blood with a 396-fold enrichment ratio and a 70.6% recovery rate at a throughput of 39.1 μl min−1, demonstrating that the platform can potentially be used in biomedical applications. [ABSTRACT FROM AUTHOR]