Artificial and Controllable Bubble Platforms for Systematic Band Structure Engineering of Few-Layer WS₂

Interfacial bubbles in two-dimensional semiconductors can generate large, spatially varying strain fields for deterministic band-structure and exciton engineering. Here we develop reproducible bubble platforms in few-layer (1-3L) WS2 using controlled exfoliation onto Au films and artificial PDMS spherical caps. The resulting tensile strain induces strong, layer-dependent reconstruction of excitonic pathways. Monolayer WS2 exhibits up to ∼150 meV direct band gap tunability and enhanced trion emission via strain-gradient-driven carrier funneling. In bilayers, strain enhances and redshifts the indirect exciton emission by reordering valley-mediated recombination channels. In trilayers, strain activates momentum-forbidden or dark-exciton-related states and modifies competing indirect recombination pathways. These results establish bubble-induced strain as a programmable route to exciton control and band-structure engineering in two-dimensional semiconductors.