Hollow Polyaniline Microspheres Encapsulated in Eutectogels for Multimodal Flexible Sensors toward Human Health Monitoring

Flexible sensors based on eutectogels are garnering significant interest for their potential applications in wearable devices and human health monitoring. However, developing flexible sensors that possess self-adhesive properties, excellent mechanical strength, high sensitivity, and multimode sensing capabilities remains a challenge. Herein, multimodal flexible sensors with hollow polyaniline (HPS) microspheres encapsulated in eutectogels (HPS-PSH gels) are fabricated via photoinitiated free radical polymerization of sulfobetaine methacrylate (SBMA) and 2-hydroxyethyl methacrylate (HEMA) in deep eutectic solvents (DES). The HPS-PSH gels display high tensile strength (up to 200 kPa), satisfactory stretchability (up to 800%), and strong self-adhesive properties. Notably, the addition of HPS microspheres significantly boosts the sensitivity of HPS-PSH gel strain sensors in the low strain range, with gauge factors (GF) increased by more than seven times in the strain range from 0 to 50%. The pressure sensors demonstrate high sensitivity (GF = −34.93) in the range of 0 to 2 kPa and feature a rapid response time of 81 ms. Additionally, the temperature sensors have a broad operating range (−20 to 100 °C). Consequently, multimodal flexible sensors can effectively monitor human activities and physiological signals, including respiration and emotions, over a wide temperature range. Given their exceptional performance, HPS-PSH gels exhibit promising potential applications in wearable technologies and health monitoring.