Temperature- and pressure-sensitive ionic conductive elastomer for respiratory monitoring and human motion sensing

Abstract

Real-time and stable monitoring of human motion and respiration is vital for health evaluations. Although conventional monitoring is realized through inflexible chip sensors, most of these devices lack portability, high accuracy, and wearing comfort. In this work, a pressure- and temperature-sensitive free-liquid ionic conducting elastomer sensor was fabricated by combining self-healing polyurethane (PU) elastomer and bis(trifluoromethane) sulfonimide lithium salt (LiTFSI). The flexible sensor shows excellent tensile strength (approximately 1.2 MPa), prominent stretchability (approximately 900%), outstanding ionic conductivity (4.02 × 10⁻³ S m⁻¹ at 25 °C), and obvious self-healing properties after mechanical damage. This sensor also exhibits excellent pressure-sensing performance, and detects different types of deformation of the human body with high sensitivity (gauge factor approximately 5.37) and cycling stability. In addition, the thermistor sensitivity of this sensor can reach an outstanding 5299 K, and it exhibits satisfactory stability when switching between high and low temperatures. More interestingly, this sensor can distinguish different respiration patterns and the breath rate and depth during different physical activities. Furthermore, the breath monitoring alarm system can visualize breathing and apnea situations in real-time. This work provides a promising strategy for the preparation of functional ionic conductive elastomer sensors used in the real-time monitoring of human health.