Patent ID: 7662268

Claim:
A method for measuring the zeta potential of the cylinder's outer surface, comprising: providing a cylinder having a first radius and a reference tube having a second radius, wherein the first radius is smaller than the second radius; the cylinder is placed coaxially inside the reference tube, and the channel existing between the cylinder and the reference tube forms a annular flow channel; introducing a solution to the annular flow channel; the solution is forced by a pressure difference ΔP to flow through the annular flow channel; and performing a measuring process to measure the streaming potential difference Ē between the two ends of the annular flow channel by electrodes, wherein the measuring process comprises calculating the zeta potential ξ m of the cylinder's outer surface from the following equation: E _ Δ ⁢ ⁢ P == - D μ ⁢ ⁢ k ⁢ ( ζ m + ζ ref 2 ) ⁢ F where D is the permittivity, ζ ref is the zeta potential of the reference tube, μ is the viscosity of the solution, k is the electric conductivity of the solution, and F is a correction factor for the electrokinetic model.