Sensing of inorganic ions in microfluidic devices

The past two decades witnessed the widespread adoption of microfluidics for miniaturized and automated chemical analysis. Microfluidic techniques require less sample, consume less reagents, and may enhance the sensitivity, precision, response time, and throughput of the analytical methods. The integration of multiple components and functionalities in microfluidic chips can further lead to fully automated Micro Total Analysis Systems (Lab-on-a-Chip). This review focuses on chemical and biochemical sensing of inorganic ions including electrolyte cations, heavy metal ions, and small anions in microfluidic devices. We provide an overview on how different optical and electrochemical ion sensing schemes based on liquid sensing phases or solid sensing phases can be coupled with microfluidics. Various microfluidics platforms including continuous-flow microfluidics, droplet microfluidics, digital microfluidics, centrifugal microfluidics, cell-based microfluidics, paper-based microfluidics, and wearable microfluidics are covered. The sensing principle, chip material, device fabrication, detector configuration, and analytical performance are presented for selected systems. This review concludes with a brief outlook on how microfluidic ion sensors may be further advanced.

Automated summary

This review focuses on the widespread adoption of microfluidics for chemical analysis in the past two decades, with a particular emphasis on the sensing of inorganic ions in microfluidic devices. Various ion sensing schemes and microfluidic platforms are covered, providing insights into the development and potential advancements of microfluidic ion sensors.