The present invention relates to a high through-put system for determining and/or monitoring electrophysiological properties of ion channels of ion channel-containing membranes, typically lipid membrane-containing structures such as cells. In particular, the invention provides a substrate which provides means for automatically positioning cells at measuring sites using electroosmotic flow in canals formed on or in the substrate. The electroosmotic flow is generated and controlled by electroosmotic flow pumps integrated on the substrate or positioned in relation thereto. Thereby, cells can be positioned in favorable measurement configuration at a plurality of sites for performing testing and measurements. Also, the invention relates to a main electric circuit for performing testing and measurements on a plurality of cells in parallel.