Garment-integrated wearable sensing for knee joint monitoring

Abstract

Body monitoring is one of the most intuitive and direct applications for technologies that are wearable. Wearable devices are capable of detecting body movements using wearable sensors, and using signals to capture anomalies as well as good patterns in our daily activities. Clothes provide the most accessible platform for embedding sensors and electronic components, preserving imperceptibility and user comfort, especially for long term body monitoring applications. Both perceptibility and comfort variables are associated with the willingness of the user to wear the device and with the quality of the data captured (that should reflect the unbiased wearer activity as if the user would not be wearing any device).

Monitoring Methods of Human Body Joints: State-of-the-Art and Research Challenges

“…For example, some systems are based on optical fiber sensors which measure the attenuation of the transmitted optical signal power which is correlated with the bending angle of the fiber [25,26,27]. Other systems used textile-based conductive wire sensors or flex sensors in which the joint angle is proportional to the change in the sensor’s resistance [37,38,39,40,41]. However, compared to other sensor technologies, inertial measurement unit (IMU) sensors are now being increasingly used to measure the joint angle.…”

“…The measurement of a joint motion includes both its angle and orientation. Therefore, joint monitoring systems based on goniometer [17,29], optical fiber sensors [25,26,27] or flex sensors [37,38,39,40,41] cannot be used to monitor joint motion since they can only measure single-axis movement which is interpreted as an angle. To estimate both the angle and orientation of joints, the most common technique is imaging or video-based tracking where the visual data of several human joint actions are captured to estimate joint motions using anthropometric constraints (size, shape and composition of the human body) and known joint locations in reference images/videos by applying image processing techniques [32,33].…”

“…Sensors are the fundamental elements of a joint monitoring system to measure the physiological parameters—angle, range of motion and posture—of joints. Various research groups [16,17,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82] have used different sensor types to build joint monitoring systems. Some systems were developed using a single sensor; others were assembled with a combination of multiple sensor technologies using data fusion methods.…”

“…The shape of the sensor will change with the applied force, causing the resistance change between two measuring points. Therefore, the flex sensor is convenient for wearable joint monitoring systems by integrating it with comfortable garments [38,39,40,41]. The flex sensor is usually stitched to the flexible and skin-tight garment across the joint to be monitored.…”

“…Whenever the joint bends or stretches, the pressure changes on the sensor which causes the variation of its electrical properties (resistance). This resistance variation due to the joint movement can be measured using an electronic system to quantify the joint angle [40]. Textile-based highly stretchable strain sensors are also used by some researchers for human joint monitoring [43,44,45,46,47,48].…”