Stress-induced tip engineering of micro-hyperbolic structures for enhanced liquid repellency.

Surface functionality in micro- and nanostructured materials is highly sensitive to geometric modifications, yet methods that enable fine structural tuning through facile and scalable fabrication remain limited. We report a method to induce controlled tip bending in micro-hyperbolic (MH) structures via metal-specific thin film deposition. When a metal layer is thermally evaporated onto the polymeric MH structures, residual stress drives directional tip deformation: tensile stress from gold (Au) causes bending toward the metal-coated side, while compressive stress from aluminum (Al) induces bending toward the polymer side. The bending magnitude is governed by the initial taper angle and explained by Stoney's formula. The resulting tip-modified MH (TMH) structures and their polymer replicas exhibit doubly re-entrant geometries that enable robust and durable liquid repellency, even against low-surface-tension liquids such as hexadecane. This approach simplifies microscale geometric tuning and supports scalable replication, offering practical utility in liquid manipulation, adhesion control, and engineered surface functionality.