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Separation of blood plasma or serum from blood is essential for accurate analysis. Conventional blood separation requires instrumentation, reagents, and large sample volumes, limiting this process to laboratory environments with trained personnel. Full implementation of effective blood separation and analysis on microliter sample volumes for point of care (POC) diagnostics has proven extremely challenging resulting in a growing market demand, with common challenges such as expensive device fabrication processes or devices being comprised of materials which are not easily disposable. We developed a membrane-based wicking microfluidic device which is made using a simple fabrication process. This device uses a unique 3D flow channel geometry, fabricated in a polycaprolactone-filled glass microfiber membrane, to efficiently separate microliter sample volumes of blood. Colorimetric assay chemistries were integrated to demonstrate utility of these devices in POC diagnostics. The devices are capable of separating both fresh and anticoagulant-treated blood at microscale sample volumes (

Copper is widely applied in industrial and technological applications and is an essential micronutrient for humans and animals. However, exposure to high environmental levels of copper, especially through drinking water, can lead to copper toxicity, resulting in severe acute and chronic health effects. Therefore, regular monitoring of aqueous copper ions has become necessary as recent anthropogenic activities have led to elevated environmental concentrations of copper. On-site monitoring processes require an inexpensive, simple, and portable analytical approach capable of generating reliable qualitative and quantitative data efficiently. Membrane-based lateral flow microfluidic devices are ideal candidates as they facilitate rapid, inexpensive, and portable measurements. Here we present a simple, chromatographic separation approach in combination with a visual detection method for Cu2+ quantitation, performed in a lateral flow microfluidic channel. This method appreciably minimizes interferences by incorp...

Membrane based microfluidic devices have gained much popularity in recent years, as they make possible rapid, inexpensive analytical techniques that can be applied to a wide variety of areas. The ability to modify device hydrophilicity and hydrophobicity is critically important in fabricating membrane based microfluidic devices. Polar hydrophilic membranes, such as glass microfiber (GMF) membranes, hold great potential as they are inexpensive, chemically inert, and stable. Filling of these membranes with non-polar polymers such as polycaprolactone (PCL) converts the hydrophilic GMF into a hydrophobic medium. Controlled alteration of the surface chemistry of PCL/GMF substrates allows for the fabrication of microfluidic patterns on the surface. Using this approach, we have developed a simple and rapid technique for fabrication of highly adaptable complex multidimensional (2D and 3D) microfluidic pathways on a single membrane. PCL-filled GMF media were masked and selectively exposed to oxygen radicals so that the exposed surface became permanently superhydrophilic in its behavior. The desired microfluidic pattern was cut into the mask prior to assembly and exposure, and the mask was removed after exposure to reveal the ready-to-use microfluidic device. To verify and demonstrate the performance of this novel fabrication method, a colorimetric total protein assay was applied to the determination of protein concentrations in real samples.

This article describes a low-cost method for rapid fabrication of paper-based microfluidic devices using an aerosolized polymeric solution and substrates masked with painter's tape. This approach requires only a few simple tools and uses low-cost supplies to achieve fully functional microfluidic paper-based analytical devices. The method is capable of producing devices with minimum hydrophilic channel widths of 482 ± 4 μm, with the channel height being dictated by the substrate thickness. Complete hydrophobic barriers can be achieved with widths of only 257 ± 2 μm. This technique enables two dimensional (2D) fluidic pattern fabrication on a single membrane while complex three dimensional (3D) fluidic pattern fabrication is possible by simply incorporating a stack and lamination step. Devices built using this approach were applied in two clinical diagnostic applications: quantitative colorimetric assays for protein and for creatinine.

Described is a new approach to building a microfluidic quantum dot wavelength-ratiometric sensor system for quantifying copper in water and biological samples. This simple-to-use, low-cost, sensitive analytical method has great utility as an indicator and quantitative tool, and we have applied it here with copper as the target analyte. CdTe quantum dots of two different sizes, emitting green and red light, are utilized as fluorophores. The green dot is used as a constant emitter and is encapsulated in a silica shell. The red dot, which is immobilized on the silica surface, is quenched in the presence of copper. The dual emission of the quantum dot wavelength-ratiometric sensor results in a fluorescence color change from red to green, identified visually, corresponding to the absence or the presence of copper. The wavelength-ratiometric sensor is mixed with microcrystalline cellulose and dropcast on a microfluidic chip, made of poly(methyl methacrylate) and assembled using polycaprolactone. Red and green intensity values from the RGB system are used as analytical signals for the calibration curve. Copper in water samples is quantitatively determined by constructing a Stern–Volmer plot in the range of 1–30 mg L−1. For serum samples, absolute values of red and green intensity were plotted to mitigate non-linearity in the Stern–Volmer plot. The microfluidic format of this quantum dot wavelength-ratiometric sensor makes rapid, low-cost testing feasible and convenient for copper detection, directly addressing a diagnostic goal.

Copper is widely applied in industrial and technological applications and is an essential micronutrient for humans and animals. However, exposure to high environmental levels of copper, especially through drinking water, can lead to copper toxicity, resulting in severe acute and chronic health effects. Therefore, regular monitoring of aqueous copper ions has become necessary as recent anthropogenic activities have led to elevated environmental concentrations of copper. On-site monitoring processes require an inexpensive, simple, and portable analytical approach capable of generating reliable qualitative and quantitative data efficiently. Membrane-based lateral flow microfluidic devices are ideal candidates as they facilitate rapid, inexpensive, and portable measurements. Here we present a simple, chromatographic separation approach in combination with a visual detection method for Cu

Due to the rapid expansion in hydraulic fracturing (fracking), there is a need for robust, portable and specific water analysis techniques. Early detection of contamination is crucial for the prevention of lasting environmental damage. Bromide can potentially function as an early indicator of water contamination by fracking waste, because there is a high concentration of bromide ions in fracking wastewaters. To facilitate this, a microfluidic paper-based analytical device (μPAD) has been developed and optimized for the quantitative colorimetric detection of bromide in water using a smartphone. A paper microfluidic platform offers the advantages of inexpensive fabrication, elimination of unstable wet reagents, portability and high adaptability for widespread distribution. These features make this assay an attractive option for a new field test for on-site determination of bromide.