Electric‐Field Distribution at the End of a Charged Capillary—A Coupling Imaging Study

The electric‐field distribution at the end of a charged capillary system is detected using a scanning electrochemical microscopy (SECM) coupling imaging mode. A theoretical model based on the resistance of solution at the capillary end describes the three‐dimensional distribution of the electric field. The effect of the detection electrode position and separation high voltage on solution potential is observed and analyzed. Results demonstrate that the electric field at the end‐channel shows an isopotential contour changing from a disk shape into a hemispherical shape when leaving the capillary opening. The solution potential decreases along the central axis of the capillary to the detection reservoir. In the same scanning plane, the solution potential decreases along the radial direction. Increase of the separation high voltage results in the increase of the absolute solution potential but does not change the relative spatial electric‐field distribution.