<p>A robust and scalable fabrication strategy is presented for three-dimensional dumbbell-like pillar nanostructures through the combination of columnar thin film engineering and selective wet etching A Ni/Cu/Ni multilayer was deposited by low-temperature magnetron sputtering, where lattice-controlled growth led to vertically aligned grain boundaries and well-defined columnar morphology. The inner Cu layers were selectively removed through top-down wet etching, while the outer Ni layers remained intact, forming voided 3D structures with increased surface area. XRF analysis confirmed a consistent Cu reduction rate of approximately 5.4% per minute, indicating controllable etching behavior. Electrical characterization demonstrated that the nanostructure geometry can be effectively tuned to optimize electrical performance while maintaining structural integrity. Mechanical properties assessed via sphero-conical nanoindentation confirmed that hardness and structural integrity were preserved, owing to the mechanical stability of the Ni framework and stress redistribution through the dumbbell-like geometry. The combination of vertical alignment, selective etchability, and mechanical durability highlights the potential of this approach for producing high–surface-area nanostructures with application-specific functionalities. The process is cost-effective and lithography-free, making it suitable for scalable fabrication of nanostructures with tunable properties. Potential applications include gas sensors, catalysis, and micro- or nanoelectronic devices where both electrical conductance and mechanical stability are required.</p> Graphical Abstract <p></p>