Optimising electrode surface area to minimize power consumption in a cortical penetrating prosthesis

In the design of cortical stimulating prostheses for applications such as vision perception or motor control it is preferable to use wireless power and data transfer to maintain a biological barrier to infection. This puts a constraint on the amount of power that can be supplied to the implant, in turn limiting the power that can be used for stimulation. Design of electrodes for such prostheses have considered factors such as efficiency of stimulation and penetrating capacity; here we consider the design of electrodes from the power consumption perspective. We use the simple electrode geometry of a sphere to determine if the surface area of the electrode can be chosen in order to minimize the power consumed during stimulation. As is known to happen when an electrode is inserted to penetrate into brain tissue, we have assumed that, due to mechanical damage from electrode insertion and the response of brain tissue to the foreign body of an electrode, there will be a kill zone around the electrode where no viable neurons are present. Using realistic thicknesses for the kill zone from the published literature and our own unpublished work, we demonstrate that when the width of the kill zone is known, an electrode´s surface area can be chosen so that the power consumed during stimulation is minimized.