Controlling Breakup of a Liquid Filament: From Edge Melting to Thermal Scissors

This talk investigates thermal effects in the dewetting of liquid metal nanostructures deposited on thermally conductive substrates and irradiated by external heat sources. We consider regimes where in-plane heat conduction within the substrate is relevant. An asymptotic long-wave model is developed that couples free-surface evolution of the liquid metal with three-dimensional heat conduction in both the metallic structure and substrate. To solve the resulting system efficiently, we implement a high-resolution 3D GPU-based simulation framework that captures the self-consistent evolution of both thermal fields and liquid interfaces over large computational domains.

We focus on the controlled breakup of a molten filament surrounded by nanopillars. These pillars enhance localized heating due to thermal conduction and, through viscosity-mediated effects, promote Rayleigh-Plateau-type instabilities that lead to breakup. We demonstrate that lateral positioning, radius, and spacing of the pillars serve as tunable parameters that enable precise control of filament breakup, a mechanism we refer to as ``thermal scissors". The simulations reveal a bifurcation in behavior as the distance between the filament and neighboring pillars decreases: the size of the resultant central droplet drops sharply beyond a critical threshold. At larger distances, inter-pillar spacing governs the final droplet size, offering an additional layer of design flexibility. These findings build on our recent results demonstrating ``thermal crowding" (see Phys. Rev. Lett. 133, 214003 (2024)) and suggest a versatile route for guiding nanostructure evolution using substrate geometry and thermal engineering.