In the study of the transport properties of electrolytes through nanochannels , surface effects become very important. One of them concerns the interactions due to electrostatic charges that may be present on the surface of the channels-wall. Being able to measure the electrical potential that these charges produce at a distance from the wall (namely the Zeta potential of the wall) is often crucial for the understanding and improvement of membranes properties.
However, to my knowledge no device that would allows this kind of measurement is currently commercialized. I developed mine. It is based on the measurement of the transmembrane voltage (namely the streaming potential) that appears when an electrolyte solution flows through the channels.
This very simple and inexpensive device has been successfully used for the characterization of nanoporous alumina membranes.
Electrical surface properties of nanoporous alumina membranes: influence of nanochannels curvature, roughness and composition studied by electrokinetic experiments, Phys. Chem. Chem. Phys., 25: 28150 (2023) , PDF