Comprehensive multi-physics modeling of thermally sustained microdischarges at atmospheric pressure: A coupled PIC/MCC–DSMC approach

Optimization of microfluidic plasma devices hinges on accurate characterization of microscale plasma–fluid–thermal coupling, a process that cannot be reliably captured by traditional single-timescale models. Here, we develop a novel self-consistent model that couples particle-in-cell/Monte Carlo collision, direct simulation Monte Carlo, and thermal conduction modules, each operating on its own tailored timescale. This model enables 1 s steady-state simulations of atmospheric-pressure direct current argon microdischarges in a 100-μm gap with a hot tungsten cathode. Quantitative results reveal that inter-electrode gas thermal conduction (1.6×106 W m−2) plays a dominant role in governing the system energy balance, thermal state of the neutral gas, and overall discharge dynamics. A 30 K drop in cathode temperature (from 2400 to 2370 K) leads to a 14% decrease in discharge current and a 68% increase in plasma dynamic resistance. We demonstrate that time-resolved gas–electrode thermal interactions govern transient plasma dynamics and device thermal management, while also showing that conventional models with fixed temperature assumptions introduce non-negligible errors in predicting key plasma parameters. This coupled model provides a robust numerical framework for the design and optimization of thermally sustained microdischarge devices.