Pulse-Clamp Technique for Characterizing Neural-Stimulating Electrodes

Abstract

A reliable test methsod is required to ensure adequate charge-injection capability for high-resolution neural-stimulation applications that demand both a large amount of charge injection and a small electrode size. A pulse-clamp circuit is designed and employed to characterize the electrode charge-storage capability that will allow different electrodes to be quickly and accurately compared. The custom circuit, which consists of commercial components, has a switching charge noise of and a switching time of . Pulse-clamp measurements are performed on flat platinum electrodes in saline solution in air with long pulses at a charge density of up to . Results indicate a safe charge-injection limit of , and a hydrolysis-dominated regime above . Comparing different electrode sizes indicates that the charge-storage capability of an electrode is proportional to its surface area. The scalability of the pulse-clamp technique allows it to be used to accurately quantify the roughness of a surface modification. Simulation program with integrated circuits emphasis simulation is used to extract the electrode capacitance and resistance parameters. These parameters, which can vary, depend strongly on the injected charge density.