The propagation delay of electrical signals in saline using electric potential sensors

This paper describes the application of a novel electric potential sensor to the measurement of the propagation delay of electrical pulses in a saline environment. This is achieved non-invasively through weak capacitive coupling to a novel electric field sensor. An experimental test cell is used to demonstrate that in an environment consisting of a polar liquid we are able to localize the position of a pulse, as well as determine its amplitude and shape. These are the basic requirements for implementing an imaging system based on this technology. Results are presented which show a spatial resolution of better than 0.23 mm using this propagation delay method. The paper includes a discussion of the effect of salt concentration on the electrical conductivity, propagation delay and velocity. The applicability of the sensor to the detection of signals originating from nerve fibres is discussed with preliminary data acquired from a 100 µm diameter glass coated micro-wire immersed in saline.