Textile-Based Strain Sensor for Real-Time Bending Angle Monitoring of Soft Joints

This paper presents the design, fabrication, and evaluation of a textile-based strain sensor integrated into a soft robotic joint for real-time monitoring of bending angles. The proposed sensor consists of a conductive fabric encapsulated in a flexible silicone substrate, created using a custom co-casting process that enables seamless integration without compromising structural compliance. Electromechanical characterization under tensile and compressive loading demonstrated a strong piezoresistive response, with a gauge factor (GF) of 77.76 under tensile strain and 9.24 under compression, within working ranges of 6–12% and 3–14%, respectively. The sensor was embedded into a soft joint with asymmetric geometry to assess directional sensitivity and real-time performance. Experimental results confirmed reliable bidirectional strain detection and an over 500% increase in resistance under tensile bending. A second-order polynomial model accurately mapped the sensor’s resistance changes to joint bending angles (10°–25°), achieving R2values above 0.67 in both tensile and compressive configurations. These findings validate the sensor’s potential for real-time posture estimation in wearable and soft robotic systems.