A Microfluidic Chip That Detects PFAS and Pharmaceutical Pollutants Directly from Muddy Water

Environmental monitoring, drinking water safety testing, and food safety inspection all share a common problem: real-world samples are rarely clean. Water drawn from a stream contains sediment. Agricultural runoff carries soil particles. Food extracts contain matrix components that conventional analytical instruments cannot handle directly. Before any measurement can be taken, the sample must be processed - filtered, extracted, and concentrated in a series of steps that add time, cost, and the risk of losing the very contaminants being sought.

Filtration is the standard first step. But filtration is not selective: when solids are removed, trace-level contaminants that have adsorbed onto particle surfaces may be removed along with them. The result is a systematic undercount of pollutant concentrations in samples that contain suspended solids - exactly the kind of samples most relevant to real environmental conditions.

A joint research team led by Dr. Ju Hyeon Kim at the Korea Research Institute of Chemical Technology (KRICT), in collaboration with Professor Jae Bem You's group at Chungnam National University, has developed a microfluidic device that bypasses filtration entirely, extracting target pollutants directly from solid-containing samples in a single automated step.

How the Trap-Based Device Works

The device's design solves the solid-sample problem through geometry. A small volume of extractant - the solvent into which target pollutants preferentially partition - is confined inside a microchamber trap. The sample solution, including any suspended solids it contains, flows continuously through an adjacent microchannel. The extractant droplet stays put while the sample passes by.

Target compounds migrate from the flowing sample into the stationary extractant by diffusion and partitioning, driven by their chemical affinity for the extractant over water. Solid particles in the sample - sand, soil, food matrix - pass through the channel without entering the extraction chamber and without interfering with the extraction. After the extraction cycle completes, the enriched extractant droplet is retrieved and analyzed directly.

This configuration achieves several things simultaneously. It eliminates the filtration step. It concentrates the analyte from a dilute sample into a small extractant volume, improving detection sensitivity. And it does so in a format that is compatible with automation and miniaturization - addressing one of the persistent barriers to field-deployable environmental monitoring.

Demonstrated Performance

The researchers demonstrated the device with two target compounds selected to represent different pollutant classes. The first was perfluorooctanoic acid (PFOA), a representative PFAS compound that is among the most studied and regulated forever chemicals due to its environmental persistence and documented health effects. PFOA signals were detectable within five minutes of sample introduction.

The second was carbamazepine (CBZ), an anticonvulsant pharmaceutical that is a common pharmaceutical residue in water systems - detectable in rivers and groundwater globally due to its incomplete removal by conventional sewage treatment. CBZ was extracted directly from sand-containing slurry samples without any filtration pretreatment, with the extracted sample subsequently analyzed by high-performance liquid chromatography. Both extractions were performed with high reliability.

Significance for Environmental Monitoring

PFAS contamination in water and soil has become a priority regulatory issue across the United States, European Union, and South Korea. Current analytical workflows for PFAS in complex environmental matrices typically require laboratory infrastructure, substantial pretreatment time, and skilled operators. A compact, filtration-free extraction platform that produces PFAS signals in five minutes represents a meaningful step toward faster and more accessible environmental testing.

The platform's ability to handle solid-containing samples without modification is particularly relevant for PFAS monitoring, given that PFAS compounds are known to adsorb onto soil particles and sediment - meaning that filtration-based approaches systematically underestimate their presence in samples that contain those materials.

Dr. Kim noted that integrating multiple pretreatment steps into a single process offers substantial advantages for on-site analysis and automated monitoring systems. KRICT President Young-Kuk Lee emphasized the potential of the technology to enhance the reliability of environmental and food safety analyses that directly affect public health.

The study was published as a cover article in ACS Sensors in December 2025, with Dr. Kim and Professor You as corresponding authors and Sung Wook Choi as first author. The research was supported by the KRICT Core Research Program, the National Research Foundation of Korea, and the Korea-Switzerland Innovation Program.