Thermocapillary Effects in the Evaporation of Heated Sessile Droplets

This work investigates in detail the evaporation-driven dynamics of reactive silver-ink sessile droplets that are relevant to high-precision inkjet printing of conductive tracks and pads. A two-dimensional axisymmetric numerical framework is developed in COMSOL Multiphysics to resolve, in a coupled way, heat transfer, fluid flow, species transport, and free-surface motion during droplet drying. Substrate temperature, solvent composition, and non-uniform evaporation patterns are systematically varied to quantify their influence on internal recirculating flows, compositional gradients, and final silver particle deposition. The results demonstrate that combining moderate substrate heating with a binary water/ethylene-glycol solvent can generate strong thermocapillary circulations that suppress the classical coffee-ring effect and promote more homogeneous particle distributions. The modeling framework therefore provides practical guidance for optimizing ink formulation and thermal processing conditions in printed electronics, and it offers a bridge between commonly used simplified models and more advanced, fully coupled simulations.