Complex hollow metallic microstructures are essential for microelectromechanical systems (MEMS), lab-on-a-chip microfluidics, and bio-integrated devices, yet their fabrication remains challenging because geometric complexity, microscale precision, and high aspect ratios must be satisfied simultaneously. This study proposes filament-guided electrolyte–column electrodeposition (FG-ECD), which couples a removable filament template with a nozzle-confined electrolyte column to define internal channels in situ during localized metal growth, thereby avoiding the collapse risks associated with conventional template removal routes. A two-dimensional axisymmetric multiphysics model reveals that the embedded filament reorganizes the electrolyte into a stable annular flow and shifts the cathodic current density maximum from the substrate toward the advancing dome front, establishing a self-consistent, quasi-stable localized reaction zone, while a parametric sweep shows that the total current scales the current density magnitude without altering its spatial profile. Experiments demonstrate that a current of 3.6 mA produces smooth dome front growth at approximately 20 μm/min, whereas 5.5 mA triggers sustained hydrogen evolution and a transition to cellular deposition. Under optimized conditions, straight, 540° spiral, and R-shaped dual-channel hollow nickel microstructures were fabricated with continuous, collapse-free internal channels of 50 ± 5 μm, aspect ratios exceeding 10:1, and dimensional accuracy within ±35 μm. FG-ECD provides a low-temperature processing route for complex hollow metallic architectures and offers process regulation principles based on co-regulation of the flow field and current density for electrochemical microfabrication.

Programmable hollow metallic microdevices with lateral outlets are attractive for distributed fluid handling, but integrating an axial lumen, side channels, and a sealed distal tip remains fabrication-intensive. Here, a core-filament jet electrodeposition (CF-JED) strategy combines segmented electrolyte-jet operation with sacrificial nylon-fiber templating to fabricate multichannel nickel microtubes. An 80 μm nylon core defines the axial lumen, whereas 50 μm transverse and helical fibers prescribe lateral channels. Interrupting the jet creates the in situ assembly interval for template placement; resumed localized electrodeposition encapsulates the fibers and can close the distal tip, and physical pull-out releases the channels without chemical dissolution or drilling. Stable growth was obtained at 2.5 mA with an axial growth rate of approximately 15 μm·min⁻¹. Micro-computed tomography revealed a 50 ± 5 μm radial channel and a 76 ± 6 μm axial lumen interconnected within the sealed-tip structure. SEM/EDS confirmed open lateral apertures and nickel-rich walls, while water-immersion gas testing provided qualitative evidence of channel interconnectivity. CF-JED therefore provides a template-defined route to programmable multichannel hollow-metal microstructures; direct liquid-flow, mechanical, and biological validation remain necessary for application-specific use.