The electrostatic potential at a solid-liquid interface (i.e., the zeta potential) is a dominant factor in electric adsorption and microchannel flows. This study proposes a fluorescence-based technique for obtaining color image of modified surface and directly measuring zeta potential. The evanescent wave is used as an excitation light for anions and cations that emit fluorescence at two different wavelengths. Patterns of self-assembled monolayers in a closed microchannel were visualized and their zeta potential distributions were measured. This technique will contribute to development of technical applications in the fields of microfluidics and material science.
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