CFD analysis was conducted using COMSOL Multiphysics 5.2 (COMSOL, Burlington, MA, USA), and the details of the simulation conditions are reported in previous studies. We designed the geometric model based on the dimensions of the SAXS device, and the ethanol concentration profile was calculated using the laminar flow model (incompressible Navier-Stokes equation) coupled with the model of the transport of diluted species. The wall condition was set to the noslip condition, and the total flow rate and FRR were set to 50 µL/min and 5, respectively.