Douglas A. Kerns

Implantable Myoelectric Sensors (IMESs) for Intramuscular Electromyogram Recording

We have developed a multichannel electrogmyography sensor system capable of receiving and processing signals from up to 32 implanted myoelectric sensors (IMES). The appeal of implanted sensors for myoelectric control is that electromyography (EMG) signals can be measured at their source providing relatively cross-talk-free signals that can be treated as independent control sites. An external telemetry controller receives telemetry sent over a transcutaneous magnetic link by the implanted electrodes. The same link provides power and commands to the implanted electrodes. Wireless telemetry of EMG signals from sensors implanted in the residual musculature eliminates the problems associated with percutaneous wires, such as infection, breakage, and marsupialization. Each implantable sensor consists of a custom-designed application-specified integrated circuit that is packaged into a biocompatible RF BION capsule from the Alfred E. Mann Foundation. Implants are designed for permanent long-term implantation with no servicing requirements. We have a fully operational system. The system has been tested in animals. Implants have been chronically implanted in the legs of three cats and are still completely operational four months after implantation.

Technical Details of the Implantable Myoelectric Sensor (IMES) System for Multifunction Prosthesis Control

The limitation of current prostheses is not the devices themselves but rather the lack of sufficient independent control sources. A system capable of reading intra muscular EMG signals would greatly increase the number control sources available for prosthesis control. We are developing a multichannel/multifunction prosthetic hand/arm controller system capable of receiving and processing signals from up to sixteen implanted bipolar differential electromyographic (EMG) electrodes. An external prosthesis controller will decipher user intent from telemetry sent over a transcutaneous magnetic link by the implanted electrodes. The same link will provide power for the implanted electrodes. This paper describes some of the technical aspects of the implant and telemetry design

IMES: An Implantable Myoelectric Sensor

We present updated progress on the design, construction and testing of an upper-extremity prosthesis control system based on implantable myoelectric sensors. The miniature injectable implant consists of a single silicon chip packaged with transmit and receive coils. Preparation for human implantation of the IMES system is underway. As part of this process, critical design improvements in the IMES implant were required. Here we report improved functionality of the IMES implant, hardened protection against electrical malfunction and tissue damage.

An Implantable Myoelectric Sensor Based Prosthesis Control System

We present progress on the design and testing of an upper-extremity prosthesis control system based on implantable myoelectric sensors. The implant consists of a single silicon chip packaged with transmit and receive coils. Forward control telemetry to, and reverse EMG data telemetry from multiple implants has been demonstrated

An implantable neural stimulator for Intraspinal MicroStimulation

This paper reports on a wireless stimulator device for use in animal experiments as part of an ongoing investigation into intraspinal stimulation (ISMS) for restoration of walking in humans with spinal cord injury. The principle behind using ISMS is the activation of residual motor-control neural networks within the spinal cord ventral horn below the level of lesion following a spinal cord injury. The attractiveness to this technique is that a small number of electrodes can be used to induce bilateral walking patterns in the lower limbs. In combination with advanced feedback algorithms, ISMS has the potential to restore walking for distances that exceed that produced by other types of functional electrical stimulation. Recent acute animal experiments have demonstrated the feasibility of using ISMS to produce the coordinated walking patterns. Here we described a wireless implantable stimulation system to be used in chronic animal experiments and for providing the basis for a system suitable for use in humans. Electrical operation of the wireless system is described, including a demonstration of reverse telemetry for monitoring the stimulating electrode voltages.

IMES - implantable myoElectric sensor system: Designing standardized ASICs

As a component of the RP2009 project, the IMES system has emerged as a strong candidate for extracting naturally-occurring control signals to be used for providing functional control of an upper body artificial limb. In earlier publications, we described various elements of this system as they were being researched and developed. Presently, the system has matured to a level for which it is now appropriate to consider application-specific-integrated circuits (ASIC) that are of a standardized form, and are suitable for clinical deployment of the IMES system. Here we describe one of our emerging ASIC designs that addresses the design challenges of the extracoporal transmitter controller. Although this ASIC is used in the IMES system, it may also be used for any command protocol that requires FSK modulation of a Class E converter.

A monolithic multi-channel amplifier for electrode arrays.

We present a monolithic microelectronic multichannel amplifier designed to facilitate measurements from multi-electrode arrays. A single silicon chip includes sixteen electrode amplifiers, along with interface and control circuitry to allow data collection through a compact 4-wire interface

NeuroTalktrade: an interface for multifunctional neural engineering ASICs

With the availability of modern application specific integrated circuit (ASIC) design tools, simulation packages, and low-cost commercial silicon foundry processes, it is becoming increasingly easy for any laboratory, or small company, to develop a custom ASIC. For stimulation, as well as recording, chips that perform specialized functions can be designed, fabricated, and tested within a time period of 2-3 months. In many cases, the desired functionality can only be obtained by using VLSI design methods. Despite this increase in ASIC functionality, as related to neural engineering applications, there exists no common interface protocol for communicating with, and controlling, neural engineering ASICs. This would be analogous to each company that manufactures PC-based systems to have no common method of communication, e.g. USB, GBIB, RS-232, etc. While it might seem elusive, we propose the specification and development of a universal interface protocol for neural engineering ASICs. We have named this interface, NeuroTalktrade.

A laboratory instrument for characterizing multiple microelectrodes

The task of chronic monitoring and characterizing a large number of microelectrodes can be tedious and error prone, especially if needed to be done in vivo. This paper presents a lab instrument that automates the measurement and data processing, allowing for large numbers of electrodes to be characterized within a short time period. A version 1.0 of the Electrode Analyser System (EAS 1.0) has already been used in various neural engineering laboratories, as well by one electrode array manufacturer. The goal of the current work is to implement the EAS 2.0 system that provides improved performance beyond that of the 1.0 system, as well as reducing size and cost.

Web technology based microelectrode characterization instrument.

In order to track the on-going changes and ultimate reliability of neural recording and stimulation arrays, it is beneficial to regularly characterize electrode arrays within the use environment. Microelectrodes used for neural stimulation or recording research can have different behaviors in-vivo vs. in- vitro, and once implanted the success of the experiment often hinges upon knowing the stability, changes, or deterioration of the electrodes. This paper describes a new instrument that is capable of batch characterizing 16 electrodes using cyclic voltammetry, electrochemical impedance spectroscopy and charge injection measurements. The latest web based technology was applied to the software design, which greatly facilitates electrode data sharing among researchers.