An Ultra‐Miniaturized Fiber Humidity Sensor Based on Near‐Parallel Ion Pathways Induced Efficient Water−Electricity Conversion

Humidity sensors are vital for ambient monitoring, but existing sensors focus on moisture absorption, overlooking the indispensable role of ion channels in the water-electricity conversion process. Here, an ultra-miniaturized fiber humidity (MFH) sensor based on near-parallel ion pathways is presented. The well-designed nanochannels significantly facilitate ion transport due to the stable charge distribution and the confined ions migration within near-parallel nanostructure, which improves the water-electricity conversion efficiency of moisture-sensitive fibers. Optimized nanochannels enable the MFH sensor to improve the response/recovery speed by ≈5 times compared to the disordered nanochannels. Additionally, the MFH sensor can be woven for ultra-miniaturization (0.50 mm²), which is much smaller than current sensors. Therefore, the integrated MFH sensor array demonstrated exceptionally high spatial resolution (sensor density of 1 mm^-1), highlighting its potential in flexible wearables. This work provides new optimization strategies and assembly means for designing the high-performance humidity sensors of the next generation.