Reconciling sensitivity and breathability in flexible iontronic pressure sensors via a hierarchical fibrous architecture

Breathability is an essential property for wearable pressure sensors used in long-term physiological monitoring. However, achieving high sensitivity while maintaining good breathability remains a significant challenge. Here, we report an electrospun fibrous iontronic pressure sensor that integrates high air and moisture permeability with high sensing sensitivity through a rationally designed hierarchical architecture. Ionic liquids are incorporated into the dielectric layer to enhance interfacial polarization, while a porous separator is introduced between the dielectric and electrode layers to increase their spacing and modulate electric-double-layer formation and contact dynamics. These three structural elements work synergistically to amplify pressure sensitivity while preserving open pathways for gas and moisture transport. The resulting sensor achieves a broad detection range of 0-350 kPa, and a sensitivity of 96.01 ± 3.12 kPa^-1 (under 0-47 kPa)-1.72-fold higher than that of the separator-free counterpart. Alongside a detection limit of 1 Pa and a response time of 120 ms, it maintained excellent breathability, with an air permeability of 12.53 mm s^-1 and a moisture vapor transmission rate of 100.28 g m^-2 h^-1. Reliable monitoring of heart rate, swallowing signals, and respiration is demonstrated under realistic wearing conditions. This study proposes a structural design strategy for regulating the sensitivity-breathability trade-off in pressure sensors, offering a viable pathway for wearable physiological monitoring.