Microfluidic Pressure in Paper (µPiP): Rapid Prototyping and Low-Cost Liquid Handling for On-Chip Diagnostics

Paper-based microfluidics was initially developed for use in ultra-low-cost diagnostics powered passively by liquid wicking. However, there is significant untapped potential in using paper to internally guide porous microfluidic flows...

Droplet Transportation through an Orifice on Electrode for Digital Microfluidics Modulations

A digital microfluidic modular interface (chip-to-chip interface) which possesses an electrode with an orifice to vertically transport core–shell droplets is presented. The electrodes were geometrically designed to promote droplet deformation and suspension. The droplets were then applied with an electrical potential for insertion into and passage through the orifice. The concepts were tested with three types of droplets at the volume of 0.75~1.5 μL, which is usually difficult to transfer through an orifice. The integration of electrowetting on dielectric (EWOD) with paper-based microfluidics was demonstrated: the droplet could be transported within 10 s. More importantly, most of the core droplet (~97%) was extracted and passed through with only minimal shell droplets accompanying it.

Fluid Control with Hydrophobic Pillars in Paper-Based Microfluidics

Paper-based microfluidics has been widely used in chemical and medical analysis applications. In the conventional paper-based microfluidic approach, fluid is propagating inside the porous structure, and the flow direction of the fluid propagation is usually controlled with the pre-defined hydrophobic barrier (e.g. wax). However, the fluid propagation velocity inside the paper-based microfluidic devices largely depends on the material properties of paper and fluid, the relative control method is rarely reported. In this study, a fluid propagation velocity control method is proposed for paper-based microfluidics: hydrophobic pillar arrays with different configurations were deposited in the microchannels in paper-based microfluidics for flow speed control, result indicates the deposited hydrophobic pillar arrays can effectively slow down the fluid propagation at different levels and can be used to passively control the fluid propagation inside microchannels for paper-based microfluidics. For the demonstration of the proposed fluid control methods, a paper-based microfluidic device for nitrite test in water was also fabricated. The proposed fluid control method for paper-based microfluidics may have significant importance for applications that involve sequenced reactions and more actuate fluid manipulation.

Evaluation of Sensitivity, Specificity, and Cost-Effectiveness of Paper-Based Microfluidics for DNA Diagnostics of Malaria versus Nucleic Acid Test (NAT) Versus Rapid Diagnostic Tests (RDT) in Resource-Limited Settings: A Protocol

Objective: The objective of the study is to compare three techniques, routinely used rapid diagnostic tests (lateral flow immune chromatography) versus nucleic acid amplification test (NAT) versus Paper-based microfluidics for DNA diagnostics of Malaria, in terms of their sensitivity and specificity as diagnostic tests in detecting malarial infection among febrile illnesses, suspected of malaria, as well as to compare their cost-effectiveness. Methodology: Three seventy febrile cases suspected of malaria with negative results with RDT will be screened by real-time PCR and DNA microfluidics techniques, sensitivity and specificity of these as screening tests will be compared. The number of extra positive cases detected by NAT gives us the yield. Cost-effectiveness analysis will be done by calculating the incremental cost-effectiveness ratio (ICER) and average cost-effectiveness ratio (ACER) for the tests. Statistical Analysis: Statistical analysis will be done using SPSS version 21. Sensitivity, specificity, Positive predictive values will be computed. Comparison of sensitivity and specificity of NAT, a paper microfluidic technique for DNA diagnostics and RDT will be carried out using McNemar’s test. Receiver operating curves will be generated separately to assess the utility of the NAT. Conclusion: The Implications of this study from the patient's perspective would mean early diagnosis which forms the tenet of control of the disease by increasing the yield. Early diagnosis at the community level would translate into the application of efficient prevention mechanisms to spread the infection. The cost-effectiveness analysis would provide a scientific basis for the adoption of the best test for the diagnosis, given the economic feasibility of the study.

Electrokinetically Assisted Paper-Based DNA Concentration for Enhanced qPCR Sensing

Paper-based microfluidics have gained widespread attention for use as low-cost microfluidic diagnostic devices in low-resource settings. However, variability in fluid transport due to evaporation and lack of reproducibility with processing real-world samples limits their commercial potential and widespread adoption. We have developed a novel fabrication method to address these challenges. This approach, known as “Microfluidic Pressure in Paper” (μPiP), combines thin laminating polydimethylsiloxane (PDMS) membranes and precision laser-cut paper microfluidic structures to produce devices that are low-cost, scalable, and exhibit controllable and reproducible fluid flow dynamics similar to conventional microfluidic devices. We present a new μPiP DNA sample preparation and processing device that reduces the number of sample preparation steps and improves sensitivity of the quantitative polymerase chain reaction (qPCR) by electrophoretically separating and concentrating nucleic acids (NAs) continuously on paper. Our device was assembled using two different microfluidic paper channels: one with a larger pore (25 microns) size for bulk fluid transport and another with a smaller pore size (11 microns) for electrophoretic sample concentration. These two paper types were aligned and laminated within PDMS sheets, and integrated with adhesive copper tape electrodes. A solution containing a custom DNA sequence was introduced into the large pore size paper channel using a low-cost pressure system and a DC voltage was applied to the copper tape to electrophoretically deflect the solution containing NAs into the paper channel with the smaller pore size. Samples were collected from both DNA enriched and depleted channels and analyzed using qPCR. Our results demonstrate the ability to use these paper devices to process and concentrate nucleic acids. Our concentration device has the potential to reduce the number of sample preparation steps and to improve qPCR sensitivity, which has immediate applications in disease diagnostics, microbial contamination, and public health monitoring.