Biomimetic nanofiber-iongel composites for flexible pressure sensors with broad range and ultra-high sensitivity

To achieve high-performance flexible pressure sensors, it is imperative to develop biomimetic devices that mimic the functional structure and sensing mechanism of human skin. Nevertheless, the creation of skin-like sensors with both ultra-high sensitivity and broad response range poses a formidable challenge. Drawing inspiration from the tactile sensing mechanisms and hierarchical structure of human skin, we engineered a nanofiber-iongel (NFIG) composite with internally graded stiffness characteristics and surface semi-embedded microstructures through the application of electrostatic spinning and droplet injection methods. The gel mimics the layered nanofiber structure of human skin, along with its ion-sensing mechanism, and comprises an ion gel infused with highly elastic PVDF-HFP nanofibers. This study explores the impact of Young's modulus and external pressure on unit capacitance, and it establishes a fiber-gel composite model to assess how the fibers influence sensor performance, encompassing ion fluxes, displacements, and alterations in electric potential. These findings reveal that the utilization of high-modulus materials enhances ion mobility, decreases the double electrical layer thickness, and augments pressure resistance. Based on these discoveries, we engineered the NFIG sensor, which exhibits ultra-high sensitivity (>10,000 kPa−1), a wide pressure range (∼1000 kPa), and exceptional stability (over 5000 cycles). Furthermore, this sensor is versatile, finding utility in a range of human monitoring contexts, array configurations, and even skateboard monitoring, thereby substantiating its promise in the fields of human-computer interaction and sports health.