Bridging Lab and Field: Capillary Microfluidics for Rapid, Low-Cost, Citizen-Based Pollution Monitoring

There is growing interest in understanding how human activities impact the environment and human health. Pollution from point and non-point sources causes lasting harm, yet information on contaminant distribution is often lacking. A key limitation is the absence of fast, simple, inexpensive testing. Microfluidic devices offer a practical solution, enabling rapid, affordable, and user-friendly monitoring by citizen scientists, reducing reliance on professional sampling and lowering costs.
We have developed paper-based microfluidic platforms that overcome conventional μPAD limitations, bridging the “lab-to-field” gap. Our key innovation is a hybrid system using hollow capillaries for fluid transport and paper for detection, unlike conventional μPADs that rely only on porous channels. This design reduces assay time to seconds, prevents analyte adsorption, and integrates multiple chemistries without cross-reactivity.
We first created a microfluidic sensor for phosphate detection in surface water, achieving ~10× lower detection limits and ~10× higher stability than prior μPADs, with >90% correlation to certified methods. Over 1,000 sensors mapped phosphate levels across Thailand, Nepal, Brazil, Chile, the USA, and Germany. Building on this, we developed a multiplexed device that simultaneously detects five heavy metals and nutrients from a single sample, allowing spatial separation of incompatible reactions, such as Fe³⁺, PO₄³⁻, and NO₂⁻, while maintaining strong recovery in real water. Recently, we developed a capillary flow-driven microfluidic device for the colorimetric determination of dissolved oxygen, achieving a limit of detection of 1.7 ppm and enabling accurate field measurements with only a smartphone.
Together, these advances show that integration of μPAD with capillary flow-driven microfluidics enables a versatile, low-cost pollution monitoring platform with sensitive, multiplexed, user-friendly assays for resource-limited settings and citizen science.