Thermoplastic Polyurethane Melt-Blown Nonwoven Flexible Sensor with Strain-Humidity Dual Response

The flexible sensors are a crucial component of flexible electronics, and their importance is becoming increasingly evident. Achieving the integration of high sensitivity, multifunctional sensing capability, and robust mechanical properties within a single flexible sensor remains a major challenge. Herein, we report a tannic acid (TA)-modified/graphene nanosheets (GNs)@thermoplastic polyurethane (TPU) melt-blown nonwoven (TA/GN@TPU MB) flexible sensor with excellent strain and humidity dual-responsive performances that can meet the multifunctional needs for complex dynamic environment monitoring. TPU MB serves as an ideal substrate owing to its large specific surface area, simple fabrication process, and good breathability. First, GN was anchored onto the surface of TPU MB through a simple ultrasonic-assisted deposition at different concentrations to obtain GN@TPU MB. Subsequently, GN@TPU MB was modified by the TA with different concentrations to achieve a humidity response function by a soaking modification method. When the concentrations of GN and TA are 20 mg/mL and 3 wt %, respectively, the resulting TA3/GN20@TPU MB sensor exhibited exceptional performance, including high sensitivity (gauge factor of 12901.98), a wide effective monitoring range (up to 260%), a fast response time (344 ms), and outstanding durability (>1000 cycles). The TA3/GN20@TPU MB flexible sensor demonstrated practical applications in real-time monitoring of both large-scale human motions (such as finger, wrist, and knee bending) and subtle facial expression changes (smiling and frowning). It was also capable of recognizing the pronunciation of various English words and detecting environmental humidity across a wide range (13–95%). This work presents a scalable and cost-effective strategy for the development of multifunctional flexible sensors based on the TPU MB.