“Capacitive” pulse shapes for platinum cuff electrodes

Artificial electrical stimulation of the peripheral nervous system is an established therapy for several pathologies and motor impairments. Therapeutic outcomes can be improved with targeted patterns of neural activation, but the required signal amplitudes to achieve this response exceed the limits for safe stimulation. This can lead to electrode corrosion and tissue damage. In this paper, we present a novel approach to pulse shape design based on the properties of the electrode-electrolyte interface. We aim to improve electrode stability at higher voltages by exploiting the potential-independent mechanisms of charge injection. We identified signal parameters associated with capacitive current flow at the platinum interface and incorporated these features into the design of cathodal pulse shapes. A pulse shape comprising 4 high-frequency `capacitive´ harmonics demonstrated a 40 fold performance benefit compared to a conventional square pulse, but irreversible reactions could not be completely avoided during current flow. However, the enhanced electrode stability with the `capacitive´ pulse shapes suggests further optimization of pulse designs according to a surface `stability function´ might allow for safe stimulation with greater electrode voltages.