Confinement‐Regulated Crystal Phase Engineering Enables Structured Semiconductor Fiber Systems for Plant Transpiration Dynamics Monitoring

ABSTRACT Transpiration is fundamental to plant life, yet its rhythms remain difficult to resolve because conventional sensing approaches perturb stomatal boundary layers, are limited to localized readouts, and struggle to reconcile moisture responsiveness with stable photodetection under dynamic humidity fluctuations. Herein, we report the first distributed plant microclimate mapping textile platform constructed from semiconductor fibers enabled by two distinct confinement‐regulated crystal phase engineering strategies. Local spatially confined thermal reconfiguration induces optimized crystallization of the semiconductor fiber core, whereas nanosphere confinement governs humidity‐triggered, reversible phase switching in the perovskite fiber cladding between CsPbBr 3 and CsPb 2 Br 5 , enabling stable photodetection together with reversible humidity response. Continuous thermal drawing and polymer coating establish a scalable route to kilometre‐scale fiber fabrication, yielding fibers with sophisticated structure that sustain linear photodetection with an on/off ratio exceeding 50 over 10 000 switching cycles while maintaining fatigue‐free humidity sensing over 600 cycles. Woven into breathable textiles, the fiber arrays enable sub‐centimetre spatial mapping and, in commercial greenhouses, resolve spatial irradiance variations as small as 10 mW/cm 2 within real microclimates, revealing microclimate heterogeneity relevant to plant transpiration and growth. These results establish phase‐engineered semiconductor fiber textiles as a scalable platform for distributed plant microclimate mapping and precision agriculture.