Titre:
Traditional and Adiabatic Neural Stimulator Circuits
Conférencier:
Shawn K. Kelly ,
Carnegie Mellon University, Pittsburgh, Pennsylvania, U.S.A.
Lieu:
NEWCAS2014, Delta Trois-Rivières ,
Date et heure:
dimanche le 22 juin 2014 de 13:30 à 17:00
Résumé: This tutorial will cover circuits for neural stimulation, including traditional current source circuits as well as recent advances in the application of adiabatic and other low-power circuits to neural stimulation. We will begin with a brief introduction into how nerve membranes work and how nerves create action potentials with ionic currents. We will learn how to artificially induce action potentials with electrical currents, and how the electric fields around a nerve can cause membrane currents (the “activating function”). We will model the electrode-tissue interface, including the transfer of charge across the interface by capacitive and Faradaic mechanisms. We will examine the requirements for safety in neural stimulation, from electrochemical reactions to tissue overstimulation, culminating in a set of limits for the designer. We will also examine circuits to monitor the electrodes during stimulation to protect against violation of the safety limits. We will cover several standard stimulation waveforms and a variety of traditional stimulator circuits, primarily biphasic current sources, but also voltage source and monophasic current source circuits. Finally, we will explore recent advances in lower-power stimulation, which rely heavily on an understanding of the electrode impedance. We will calculate the minimum possible power requirements for stimulation, see where power is being wasted, and look at architectures to reduce the waste power. A simple variable-supply current source architecture has been used in some cases to maintain the capability of high compliance voltage while allowing for lower power when possible. An adiabatic voltage step architecture creates a network of voltage supplies to step the electrode along a voltage waveform that simulates the typical biphasic current electrode waveform. A step-down current stimulator adjusts a constant current source during stimulation to reduce the required compliance. Finally, a full moving supply current source stimulator, while adding complexity, can approach the minimum stimulation power. These methods can often reduce the power consumed during neural stimulation by 50% or more. The tutorial will cover background physics, system architectures, and specific circuits for neural stimulation.
Note biographique: Dr. Shawn K. Kelly is an electrical engineer and Senior Systems Scientist in the Institute for Complex Engineered Systems at Carnegie Mellon University, and a Research Biomedical Engineer with the Department of Veterans Affairs, working on the development of a retinal prosthesis for the blind, as well as other implantable medical devices. He received the S.B., M.Eng., and Ph.D. in electrical engineering from the Massachusetts Institute of Technology in 1996, 1998, and 2003, respectively. He joined the Boston Retinal Implant Project in 1996 and developed a portable retinal stimulator for human trials for his masters and a patented low-power neural stimulator chip for his doctorate. He has joined the Department of Veterans Affairs in 2003, spent eight years as a Visiting Scientist at MIT, and joined ICES at CMU in early 2012. He leads the design and testing of the electrical systems for the retinal implant. Dr. Kelly’s particular areas of interest include neural stimulator circuit design, the electrode/tissue interface, wireless power and data transmission, power management, and assembly and packaging of implantable medical devices. He teaches a course on neural stimulation and a course on introductory circuits at CMU.
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