Development of a Conformal Textile Electrode Liner for the Purpose of Myoelectric Prosthesis Control
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Date
2013-10-09
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Johns Hopkins University
Abstract
In upper-extremity myoelectric prostheses, hard surface electromyography (sEMG) electrodes are typically placed in a rigid or semi-rigid socket worn over the residual limb. The resulting interface does not offer optimal suspension and cannot adapt to volume changes that the residual limb inevitably experiences. These volume changes can lead to electrode lift-off and electrode shift, resulting in weaker control or loss of control of the prosthesis.
The work in this thesis focuses on the development of an alternative electrode interface that we will refer to as the ``MyoLiner". The MyoLiner comprises textile electrodes embedded directly into a roll-on silicone liner to create a secure and conformal interface. By using textile as the electrode substrate, the electrodes can also be embedded and sealed in a silicone liner while maintaining the liner's suspension integrity.
We have developed both remote and active textile electrode prototypes. This thesis demonstrates the potential of these newly developed textile electrodes and establishes the groundwork for the development of a fully-integrated version of this interface.
Impedance testing with the remote textile electrodes has shown that electrode-skin impedance similar to that of conventional metal dome electrodes can be achieved with the presence of sweat or water. Noise analysis has shown that the active textile electrodes can effectively minimize power line and cable interference. Preliminary functional test results have also suggested that the textile electrodes can reliably control a prosthesis. A Cue Test showed non-significant differences in time needed to achieve 3 out of 4 conventional sEMG triggers for direct control, and a case study with a pattern recognition system has shown comparable separability of patterns during training and comparable cue completion during evaluation.
An envelope SNR study has suggested the sEMG envelope quality of the textile electrodes is not matched to the envelope quality of conventional Otto Bock electrodes. An active textile electrode design utilizing a high front-end analog gain can address this issue. Future work involves developing this next generation active textile electrode prototype and fully integrating the electrodes into a silicone liner and ultimately into a prosthesis.
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Keywords
prosthesis, myoelectric, interface, electrodes, conformal, textile, flexible