Influence of Zeta Potential–Dependent Surface Slip on the Migration of Polystyrene Particles in Microchannels

The slip on the fluid-solid interfaces is a crucial factor to consider in microfluidic studies of particle motion. It can alter the zeta potential, thus influencing the separation or focusing behavior of particles. Consequently, the zeta potential serves as a useful tool to study how surface slip impacts particle motion. In this work, the zeta potential of these polystyrene particles with various surface functional groups was measured in acidic, neutral, and basic environments. The zeta potential of the microchannel wall was also considered. The particle migration trajectory in low aspect ratio microchannels was experimentally investigated under varying flow rates and pH conditions. The radial migration probability distribution and focusing regions were roughly determined through quantitative analysis. Furthermore, the variations in peak value of radial migration density versus particle zeta potential under different flow rates were summarized. The results demonstrated that the particle radial migration in the channel differs among three surface-modified particles under varying pH conditions. Slip could affect the velocity gradient around the particle surface, qualitatively explaining these differences. This study provides experimental evidence for the slip effect on particle migration in microchannels and contributes to understanding the role of slip in particle motion at the microscale.