Development of Knitted Strain Sensor Optimized for Dumbbell Exercise and Evaluation of Its Electrical Characteristics

With growing interest in wearable technologies, the development of flexible sensors and products that can monitor the human body while being comfortable to wear is gaining momentum. However, can be directly integrated into textiles or clothing are lacking. In this study, we fabricated a knitted strain sensor that monitors elbow angles, focusing on dumbbell exercise, which is a basic exercise in sports, and verified its performance. The material of the fabricated knitted strain sensor with a plain stitch structure comprised a silver-plated conductive yarn and an acrylic/wool blended yarn. To evaluate the electrical and physical characteristics of the fabricated sensor, a textile folding tester was used to conduct 100 repeated bending experiments at three angles of 30°, 60°, and 90° and speeds of 10, 30, and 60 cpm. According to the results, the fabricated knitted strain sensor exhibits excellent elasticity, high sensitivity (gauge factor = 698), fast response, and excellent reproducibility and stability even under long-term repeated bending. Sensors with such excellent performance are expected to be used not only in real-time body monitoring but also in various wearable applications.