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Transcutaneous Electrode Technology for Neuroprostheses

Author(s):

M. Lawrence
Conference/Journal:

ETH Zurich, no. DISS. ETH NO. 18213, pp. 241
Abstract:

Neuroprostheses (NP) are devices which use electrical stimulation to artificially activate sensory nerves and motor neurons in subjects with neurological disorders (e.g. stroke or spinal cord injury). Self-adhesive transcutaneous (surface) electrodes are relatively low cost, non-invasive and easy to reconfigure for different functional requirements. However the application of transcutaneous electrical stimulation (TES) in neuroprostheses is limited by the need to accurately replace multiple sets of electrodes on the skin surface. Unwanted movements and discomfort caused by activation of superficial motor neurons and sensory receptors further limit the applicability of TES in neuroprostheses, especially for restoration of complex functions such as grasping. In this thesis new transcutaneous electrode array technology is addressed which can overcome such limitations, enabling improved functional grasping. Conductive yarns were used to embroider electrode elements and interconnecting wires directly into garments. The perceived comfort of existing and new skin interface materials was assessed, with results suggesting that surface contact area is important for reducing discomfort during TES. The results were used to design two prototype neuroprostheses to enable improved restoration of functional grasping. A custom multiplexer was designed to enable the cathode and anode positions to be dynamically switched between subsets of an array of small transcutaneous electrode elements placed on the skin. Two 30-element embroidered electrode arrays were placed above the extrinsic finger flexors and extensors, with the cathode systematically switched between each element, with the anode positioned as far away as possible. Suitable activation regions could be identified to enable selective middle and ring finger forces and functional grasps whilst maintaining wrist extension torques. A simpler neuroprosthesis with customizable electrode positions optimised for functional grasping was designed. Initial measurements indicated the electrodes could be replaced to an accuracy of 5mm. The results from this thesis demonstrate that embroidered electrode array technology can be used to simplify the design and improve the application of neuroprostheses for grasping. Future developments in recording kinematic movement from the fingers and wrist, as well as miniaturizing the stimulator switching technology are required to make neuroprostheses for functional grasping. The technology should not only be limited to restoration of functional grasping, but should also be applied in others TES applications such as electrotactile stimulation for sensory restoration.

Year:

2009
Type of Publication:

(03)Ph.D. Thesis
Supervisor:

M. Morari

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% Autogenerated BibTeX entry
@PhDThesis { Xxx:2009:IFA_3483,
    author={M. Lawrence},
    title={{Transcutaneous Electrode Technology for Neuroprostheses}},
    school={},
    year={2009},
    address={ETH Zurich},
    month=mar,
    url={http://control.ee.ethz.ch/index.cgi?page=publications;action=details;id=3483}
}
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