sEMG Sensor Using Polypyrrole-Coated Nonwoven Fabric Sheet for Practical Control of Prosthetic Hand

Abstract

One of the greatest challenges of using a myoelectric prosthetic hand in daily life is to conveniently measure stable myoelectric signals. This study proposes a novel surface electromyography (sEMG) sensor using polypyrrole-coated nonwoven fabric sheet as electrodes (PPy electrodes) to allow people with disabilities to control prosthetic limbs. The PPy electrodes are sewn on an elastic band to guarantee close contact with the skin and thus reduce the contact electrical impedance between the electrodes and the skin. The sensor is highly customizable to fit the size and the shape of the stump so that people with disabilities can attach the sensor by themselves. The performance of the proposed sensor was investigated experimentally by comparing measurements of Ag/AgCl electrodes with electrolytic gel and the sEMG from the same muscle fibers. The high correlation coefficient (0.87) between the two types of sensors suggests the effectiveness of the proposed sensor. Another experiment of sEMG pattern recognition to control myoelectric prosthetic hands showed that the PPy electrodes are as effective as Ag/AgCl electrodes for measuring sEMG signals for practical myoelectric control. We also investigated the relation between the myoelectric signals' signal-to-noise ratio and the source impedances by simultaneously measuring the source impedances and the myoelectric signals with a switching circuit. The results showed that differences in both the norm and the phase of the source impedance greatly affect the common mode noise in the signal.

Systematic review of textile-based electrodes for long-term and continuous surface electromyography recording

“…Concerning their electrical conductivity, PEDOT-PSS-coated textile electrodes showed a resistance of 35 kX at 100 Hz. 55 The PPy-based electrode reported by Jiang et al 56 has a surface resistivity <1 Â 10 5 X/sq, which is lower than that of PEDOT-PSS. However, PPy exhibits low water solubility and hygroscopicity in the ambient environment; therefore, when the electrodes become wet or humid due to skin perspiration, they may provide a more stable performance making them usable in daily life.…”

“…Four articles did not specify the size of the electrodes, and three articles reported adjustable electrode size. 56,57,61 The orientation of the electrode with respect to the muscle fiber was poorly described in the reviewed literature, although the orientation is of importance.…”

“…Textiles as support materials -'add on' Mechanical attachment (often inorganic) Sleeves 38,39 Taping Socks 63 Temporary fixture (often for testing) Electrodes fixed by elastic band 59,65 Cut and sew Jogging 68,[72][73][74] Armband/sleeves/elastic band [47][48][49]56,57,61,64,67,70,76,77,79 Integrated onto Coating Knitted fabric straps 55 Stencil printing Armband/sleeves 58,60 Integrated into Embroidery/sewing Jogging Figure 6. Wearable system integration levels.…”

“…Prosthetic hand control. Powered prosthetic hands, 38,39,41,44,45,[47][48][49]56,57,60,61,65 which are controlled by myoelectric signals, are considerably more advanced than the control strategies used to command them. 24 The myoelectrical signal sensors commonly used for prosthetic hand control are large in size and stiff, which limit the number that can be applied to the limb and cause pressure-related discomfort for users.…”

“…The use of textile-based or flexible electrodes has been explored as an alternative to common metal electrodes. 48,49,56 However, the signal quality and the motion artefacts generated by the relative displacement need to be addressed, which require the development of novel materials and textile structures, and potentially the improvement of control algorithms.…”