Numerical study of droplet thermocapillary migration on rectangular wettability-confined tracks using a lattice Boltzmann model

Thermocapillary actuation offers a simple and effective means to manipulate droplet motion, while surface modification provides a reliable method to control the thermocapillary migration of microdroplets with high accuracy and flexibility. In this study, the thermocapillary migration of droplets on single and dual-rail rectangular wettability-confined tracks under a uniform temperature gradient is investigated using a three-dimensional color-gradient thermal lattice Boltzmann model. The model's capability to simulate fluid–surface interactions is first validated through simulations of partial wetting behavior. Subsequently, droplet migration on a single track is examined and compared with that on a homogeneous hydrophilic surface. Particular attention is given to the influence of track width on droplet elongation and migration velocity, and non-monotonic dependencies are identified. Finally, droplet migration on dual-rail tracks is analyzed. A comprehensive investigation into the effects of track width, wettability, and the width of the interval region between the tracks is conducted, and the underlying mechanisms governing these effects are elucidated.