A novel functional electrical stimulation sleeve based on textile-embedded dry electrodes

Abstract

Background: Functional electrical stimulation (FES) is a rehabilitation technique that enables functional improvements in patients with motor control impairments. This study presents an original design and prototyping method for a smart sleeve for FES applications. The article explains how to integrate a carbon-based dry electrode into a textile structure and ensure an electrical connection between the electrodes and the stimulator for effective delivery of the FES. It also describes the materials and the step-by-step manufacturing processes.

Results: The carbon-based dry electrode is integrated into the textile substrate by a thermal compression molding process on an embroidered conductive matrix. This matrix is composed of textile silver-plated conductive yarns and is linked to the stimulator. Besides ensuring the electrical connection, the matrix improves the fixation between the textile substrate and the electrode. The stimulation intensity, the perceived comfort and the muscle torque generated by the smart FES sleeve were compared to hydrogel electrodes. The results show a better average comfort and a higher average stimulation intensity with the smart FES sleeve, while there were no significant differences for the muscle torque generated.

Conclusions: The integration of the proposed dry electrodes into a textile is a viable solution. The wearable FES system does not negatively impact the electrodes' performance, and tends to improve it. Additionally, the proposed prototyping method is applicable to an entire garment in order to target all muscles. Moreover, the process is feasible for industrial production and commercialization since all materials and processes used are already available on the market.

Keywords: Dry electrodes; Functional electrical stimulation; Rehabilitation; Sleeve; Smart textile.

Fig. 1

Average perceived comfort rating where 0 = most comfortable and 10 = most uncomfortable. In each boxplot, the horizontal line indicates the median and the circle the mean

Fig. 2

Average normalized torque induced with stimulation. In each boxplot, the horizontal line indicates the median and the circle the mean

Fig. 3

Average stimulation intensity values used across all participants. In each boxplot, the horizontal line indicates the median and the circle the mean

Fig. 4

Average reported sensations after stimulation with each electrode type

Fig. 5

Textile pattern of the smart FES sleeve, with its specific dimensions

Fig. 6

Sewn conductive matrix on the knitted substrate and the nonwoven thermoadhesive. a The inner side (facing skin) and b the outer side

Fig. 7

a Process of attaching the dry electrode to the textile substrate. Conductive textile threads are sewn onto the knitted and nonwoven thermoadhesive structure, then the dry electrode is fixed by thermal compression. Photo of the outer b and inner c side

Fig. 8

The smart FES sleeve for biceps: a the inner and b the outer sides, and c the prototype worn and connected