A novel asymmetric clamping cell for measuring streaming potential of flat surfaces

A novel asymmetric clamping cell is used to measure the potential of macroscopic sample surfaces. The unique design of the cell allows in-situ measurement of potentials of any flat surfaces, either solids (such as glass, plastics, metals, and ceramics) or flexible sheets (like polymer films, papers, foils, and membranes), without having to cut or shape the test surfaces to fit the measuring cell dimensions. The cell enables measurement of the streaming potential through several parallel rectangular channels formed by firmly pressing a grooved spacer against the test surface. The term asymmetric specifically refers to the unique configuration of the channels, where one of the walls (the test surface) bears a different charging property (or, more specifically, potential), compared to the other three surfaces of the channel (formed by the spacer). A mathematical formulation on the basis of Smoluchowski-Helmholtz approach reveals that the measured potential in such a cell represents the average potential of the test surface and the spacer material. Several surfaces, including clean glass disk, aminosilane modified glass, polymeric membrane, and poly(methyl methacrylate) (PMMA) plate, were tested using the cell. The potentials of the polymeric membrane obtained using the present cell were compared with the corresponding potentials measured using the traditional rectangular cell, and good agreement between the two measurements was observed. The asymmetric cell can be used in conjunction with standard commercially available streaming potential analyzers.