NUMERICAL SIMULATION OF CHARGED PARTICLE SEPARATION AND ENRICHMENT IN A PRESSURE DRIVEN DUAL-MEMBRANE ION CONCENTRATION POLARIZATION SYSTEM

Ion concentration polarization phenomenon in micro-nano fluidic devices can efficiently enrich low-concentration particles, yet there remains an issue with the separation and enrichment of multiple particles with poor separation efficiency. In this paper, we propose a particle separation and enrichment system based on the ion concentration polarization phenomenon. This system constructs two micro-nano interfaces by employing two ion exchange membranes to regulate the electric field environment experienced by charged particles. This model takes DNA and BSA as examples, which enables the differential enrichment of DNA and bovine serum albumin (BSA) in front of different membranes, thus achieving their positional separation. Numerical simulations analyze the effects of external pressure and different transmembrane voltages of the ion exchange membranes. Specifically, inlet pressure controls the fluid velocity within the channel, affecting the fluid drag force experienced by particles. The transmembrane voltage regulates the ion concentration polarization phenomenon, affecting the electric field force experienced by particles. The numerical simulation analysis demonstrates that the separation mechanism of the dual-membrane system involves the competition between the high electric field generated in different depletion zones and the fluid drag force applied to the particles. This competition scenario indicates that in front of the first membrane, the electric field force on BSA is smaller than the fluid drag force, while the opposite is observed for DNA. Simultaneously, this paper reveals the mechanism of charged particle enrichment in a pressure-driven dual-membrane system formed under ion concentration polarization. The results indicate that under V_cm1 = 5V_T, V_cm2 = 10V_T, and P₀ = 400 Pa, efficient positional separation of DNA and BSA is achievable. The enrichment multiples for DNA and BSA respectively reach 1.2 × 10⁵ and 6.0 × 10⁴. This offers a new perspective and theoretical guidance for simultaneously enriching and separating multiple charged particles and the design of multistage ion concentration polarization cascade system.