Separation and preconcentration of biomolecules using ion concentration polarization in microchannels

Ion concentration polarization (ICP) is an effective technology for preconcentrating dilute charged species in microfluidic systems for various applications across chemistry and biology. In this work, we concurrently separate and preconcentrate the biomolecules of interest from mixed samples in microchannels based on their differences in electrophoretic mobilities. By numerically solving the coupled governing equations of the Nernst-Planck, Poisson, and Navier-Stokes, we systematically study these processes under various working conditions, including electric potentials and pressure biases. Moreover, the position of each preconcentrated sample plug is determined analytically, which facilitates the positioning of biosensors in microchannels. The analytical critical (minimum) electrophoretic mobility is also introduced to ensure the preconcentration mechanism of biomolecules. Furthermore, we analytically obtain the critical external pressure biases (minimum and maximum) for separating and purifying the biomolecules of interest from mixed samples. The analytical solutions and the numerical simulations are not only consistent with each other but also compatible with experimental observations. The obtained results for the separation and preconcentration of mixed samples are expected to help improve downstream analyte detections in applications such as drug analysis, food safety, environmental monitoring, disease diagnosis, and others.