Flexible fire-extinguishing microcapsule patch for autonomous early-stage fire protection in confined electrical spaces

Abstract

Accurate prevention and control of incipient fires in confined spaces place extremely high demands on passive fire-extinguishing devices. However, conventional fire-extinguishing microcapsules are often limited by broad size distributions and the propensity of highly volatile core materials to leak, leading to delayed thermal response and performance degradation. To address this challenge, we developed a novel microfluidic platform integrating 3D-printed templates with non-planar PDMS microchannels, enabling stable and monodisperse (CV = 3.53%) core–shell encapsulation of a highly volatile perfluoro-2-methyl-3-pentanone/heptafluorocyclopentane (PFH/F7A) composite fire suppressant. By establishing a theoretical scaling law based on multiphase-flow shear and mass conservation, we achieved precise decoupled control over microcapsule diameter and shell thickness. Further thermo-fluid–solid coupled mechanical analysis revealed the underlying mechanism of the sub-millisecond “micro-explosion” upon heating, namely, the convergence of an internal vapor-pressure surge induced by core vaporization and the deterministic instability caused by thermal softening of the polymer shell. Using the target geometric parameters for device integration (average diameter of 519.1 μm, coefficient of variation (CV) = 4.87%; shell thickness of 32.6 μm, CV = 6.21%) and the optimal agent ratio (P : F = 5 : 5), we array-integrated the microcapsules into a two-dimensional flexible patch, enabling coordinated quasi-synchronous release of numerous microcapsules at the critical temperature. Macroscopic tests demonstrated that the patch rapidly extinguished an n-heptane pool fire within 5 ± 0.5 s, decisively preventing re-ignition. Moreover, under 300 °C thermal abuse for 18650 lithium-ion batteries, it delayed thermal runaway onset by an average of 355 s and reduced the peak temperature by approximately 199 °C. This work establishes a complete closed loop from the underlying dynamic mechanism to macroscopic device design, providing a new strategy for efficient and adaptive thermal safety protection in complex confined spaces.