Safe Direct Current Stimulator Design for Reduced Power and Increased Reliability

Unmet Need
Neuroprostheses, such as cochlear implants and neural pacemakers, have already been proven to be useful in varying applications. Current neuroprostheses tools typically employ biphasic pulsatile stimulation, a process where electrodes have both a cathodic phase and an anodic phase to pass charge in both directions. Direct current (DC) has also demonstrated great potential as a neuroprostheses tool; however, DC cannot be directly applied to neurons as metal electrodes have a charge injection threshold. Using DC as a means of neuromodulation over biphasic pulsatile stimulation can help to reduce neural sensitivity and spontaneous firing rate; DC also produces a firing pattern that is not phase locked to a stimulation frequency. There is a need to safely apply DC in neuromodulation technologies. Though biphasic pulsatile stimulation has been effective in some applications, there are many areas where biphasic stimulation is not suitable.

Technology Overview
Researchers from the Johns Hopkins University School of Medicine have developed a technology for a direct current stimulator that safely stimulates neural tissue without violating the charge injection limits of electrode-electrolyte interfaces. The design of this safety direct charge stimulator allows the system to produce a constant current amplitude despite changes in the gate configuration of the electrode configurations. The electronics reproduce the necessary states described in the state machine implementation and, overall, the design successfully supplies all the electronic control needs. This design will enable the development of ionic direct current as a mechanism for neuromodulation and allow DC to be used for neuromodulation.

State of Development
Systems and methods completed. Working version of prototype has also been completed.

Publications
Fridman GY et al. IEEE Transactions on Neural Systems and Rehabilitation Engineering 2013
Fridman GY et al. Conf Proc IEEE Eng Biol Soc. 2014
Fridman GY, Conf Proc IEEE Eng Biol Soc. 2017
Ou P, et al. IEEE Biomedical Circuits and Systems Conference 2017

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