A Novel Optimizing Method for the Structural Parameters of High-Temperature Thin-Film Heat Flux Sensors Based on Thermo- Mechanical-Electrical Coupled Model

High-sensitivity thin-film heat flux sensors with microsecond-level response capabilities are urgently required for advanced thermal management in aerospace and nuclear power systems, yet their operational reliability under extreme high-temperature conditions (>1700 K) remains a persistent technical bottleneck. This study presents an innovative multiphysics optimization framework combining thermo-mechanical-electrical coupling analysis with 3-D micro/nanoscale finite element simulations. Through orthogonal experimental design and interaction regression modeling, we systematically investigated the coupled effects of four critical structural parameters: substrate, thermal resistance layer, thermopile layer, and protective layer thicknesses. Key findings reveal that increasing the substrate thickness from 0.5 to 2.5 mm resulted in a 17.6% reduction in peak temperature (from 1700 to 1400 K), but led to a 39% decrease in output potential. In contrast, thickening the thermal resistance layer from 1 to $3~\mu $ m improved output potential by 56% (to $38~\mu $ V) at the expense of doubling the response time (from 4 to $8~\mu $ s). Mechanically, thicker substrates and protective layers dispersed stress (40% stress reduction at 2.5 mm substrate thickness), while excessive thermopile layer thickness ( $\gt 0.4~\mu $ m) induced localized stress concentration. The optimal configuration (substrate: 2.5 mm, thermal resistance: $1.5~\mu $ m, thermopile layer: $0.4~\mu $ m, protective layer: $1~\mu $ m) achieved a 273% performance improvement over the traditional design, balancing rapid response, high output potential, and low stress. This work establishes a dual-objective optimization paradigm resolving the inherent conflict between sensor sensitivity and structural reliability, particularly under transient thermal loads exceeding 1700 K. The proposed methodology provides critical insights for next-generation sensor design in extreme thermal environments.