Advances in the application of ion concentration polarization in paper-based microfluidic chips

One of the main bottlenecks in biochemical detection technologies lies in their limited sensitivity for low-abundance targets, particularly in complex micro-sample systems where separation and enrichment of analytes are especially challenging. Therefore, preconcentration of low-abundance samples has become a critical step in microfluidic bioanalysis. Ion concentration polarization (ICP), with its unique mechanism of forming stable particle-enrichment zones under an electric field, has attracted extensive attention for micro-scale substance preconcentration. Meanwhile, paper-based materials, characterized by their wide availability, low cost, ease of modification and processing, and excellent hydrophilicity, offer an ideal substrate for constructing microfluidic chips. Consequently, paper-based ICP preconcentration technology has gradually emerged as an important research direction in micro-scale sample enrichment. This review systematically summarizes the coupling mechanisms of ion transport, flow fields, and electric fields under porous media conditions, along with the governing equations. It further provides a detailed overview of recent applications of paper-based ICP in the separation and enrichment of proteins, nucleic acids, and microorganisms. Current research indicates that paper-based ICP technology holds promising potential for point-of-care testing (POCT), on-site environmental monitoring, and rapid analysis under resource-limited conditions, paving the way for the development of low-cost, highly sensitive microfluidic detection platforms.