Topology‐Controlled Liquid Transport Enables Long‐Term Stable On‐Skin Biointerfaces

Long‐term on‐skin sensing is constrained by sweat accumulation at the skin–device interface, which disrupts signal stability and user comfort despite advances in breathable materials. Although porous and fibrous substrates improve initial vapor permeability, they typically fail under prolonged perspiration due to localized evaporation and salt buildup. Here, we show that interfacial stability is not fully captured by porosity alone, but is strongly associated with the ability of a permeable scaffold to redistribute liquid through interconnected transport pathways. To realize this concept, we reconfigure natural wood into a permeable flexible wood (PFW) by partially deconstructing the cell‐wall matrix, increasing accessibility of hydrophilic pathways, and improving connectivity among axial and lateral transport routes. The resulting material exhibits a water‐vapor transmission rate of 136.23 g m − 2 h − 1 and retains 84.3% of its WVTR after five artificial‐sweat cycles, while dyed artificial‐sweat tests confirm efficient liquid redistribution across the scaffold. As a piezoelectric biointerface, PFW maintains 81.5% of signal amplitude after 6000 mechanical cycles under sweating conditions. These results support multidirectional liquid redistribution as an important design principle for reducing localized salt accumulation and preserving performance under repeated sweating‐related challenges, providing a strategy for engineering sweat‐stable permeable biointerfaces.