Summary

Wearable systems embedding strain sensors have gained broad acceptance for unobtrusively monitoring human joints motions. A textile-based wearable system was developed for monitoring elbow movements. Experimental trials showed promising performances of the developed wearable system for monitoring consecutive flexion-extension elbow movements.

Abstract

Background

The monitoring and analysis of human joint motion are essential in many medical specialities because they can provide clinicians and therapists useful information about post-surgical recovery or rehabilitation progresses. The elbow joint has a crucial role in daily activities. Monitoring elbow movements could provide relevant information about its functional state and for clinical and pathology diagnoses. In recent years, strain sensors based on conductive textile have gained broad acceptance in developing wearable systems to detect human joint motions, thanks to their stretchability, lightweight, high flexibility, and low cost.

AIMS
This work aims to design and fabricate a wearable system for monitoring elbow movements that should be portable, easy to wear, low cost, and applicable in clinical scenarios as a valuable medical instrument both for therapists and patients.

Methods

The wearable system consists of an elbow sleeve integrating a strain sensor based on an elastic conductive textile (EeonTeXTM LG-SLPA, Eeonyx Corporation). The sensing element was rectangular-shaped (30mm long and 10mm wide) and integrated into two polymeric layers (Ecoflex 00-30TM, Smooth-On). The sensing elements' measurement principle relies on the changes in the electrical resistance of the conductive textile as a consequence of the applied strain.
Experimental tests were performed to evaluate the performances of the wearable system during elbow movements monitoring. Pilot experiments were performed. The elbove sleeve was worn with the embedded sensor, and to perform three trials: i) flexion movement starting from 0° to 150° at steps of 30°, at five increasing speeds. Per each speed, the participant had to reach the desired angle, and to rest in that position for about 10 seconds; ii) flexion movement starting from 0° to 150° at steps of 30°, at five increasing speeds, without standing in the rest position; iii) flexion movement starting from 0° to 150° at steps of 30°, at a self-selected speed. A graduate table and a metronome were used to guide the volunteer during trials.

Results

Experimental results showed that the proposed wearable system integrating a strain sensor based on conductive textile monitored elbow flexion-extension movements in all trials. In particular, a resistance decrease occurred corresponding to the increasing strain during flexion. Results showed no discrepancy in the measurement of resistance at the different speeds for a specific angle.

Discussion

Wearable system based on flexible strain sensors could enable clinicians to monitor quantitatively human body joint kinematics. The developed wearable system showed promising results for monitoring elbow movements unobtrusively and comfortably for the user. We believe that this emerging technology could be particularly suitable for monitoring elbow movements, opening new challenging directions in clinical scenarios.
Indeed, flexible strain sensors integrated into wearable systems could effectively monitor human body joint health care.