Development of dry textile electrodes for electromiography: a comparison between knitted structures and conductive yarns

The paper presents a practical approach concerning the design, implementation and testing of dry textile electrodes for surface electromyography purposes. Several knitted structures were designed and knitted with conductive yarns, in order to compare the influence of the fabric structure in the electrode performance. The effect of the type of conductive yarn was also studied by comparing three different yarns. It was found that the textile electrodes perform well for sEMG acquisition, with a clear depiction of the muscle activity produced. There are significant differences between the structures tested and there is also some influence from the yarn used.This work is supported by Portuguese National Funding, through FCT - Fundação para a Ciência e a Tecnologia, in the framework of project EHRPhysio PTDC/DTP-DES/1661/2012 and project UID/CTM/00264/2013

Flexible Electronics for High-Density EMG Based Signal Acquisition for Upper Limb Myoelectric Prosthesis Control

The research detailed in this thesis is aimed at developing flexible electrodes for high-density control of an upper limb myoelectric prosthesis. Different flexible dry electrode materials (made from doped traditionally non-conductive substrates) were used and compared to titanium (which is the industry standard for EMG electrodes). We determined that conductivity measurements alone, (the current industry standard for characterizing electrical properties of materials), are not sufficient due to their complex impedance. We measured the skin electrode complex impedance and relationship with signal to noise ratio (SNR) and settling time. We show that complex skin electrode impedance is linearly related to the SNR of signals and that complex skin electrode impedance better characterizes the electrical properties of doped, traditionally non-conductive materials for physiological signal acquisition. Next we constructed a flexible high-density array with 128- contact points arranged in an 8 x 16 configuration to cover the entire residual limb. Myoelectric signals, and its relationship to derived time domain features of all 128 channels were extracted and represented as spatio-temporal values as 8 x 16 images to represent the muscle activity map of the residual limb. Thus, a traditional signal-processing problem is converted into an image processing problem. Obtaining High Density (HD) (128 channel) spatio-temporal information has significant merits which include: ability to easily identify the optimum myoelectric recording sites on a residual limb, ability to temporally study the onset and decline of a contraction, predicting the stage of contraction and, finally, ability to implement proportional control and fine motor myoelectric control