Directional Transport of Metallic Nanowires via Line-Contact Photothermal Shock on Microfibers

Nanotechnology faces a critical challenge in achieving precise manipulation from liquid-phase environments to solid-phase interfaces. Microfiber platforms have enabled photothermal control of nanomaterials in point-contact configurations; however, line-contact configurations-commonly encountered in practical devices-exhibit fundamentally distinct physical behaviors that remain poorly characterized. Here we demonstrate, through integrated multiphysics modeling and experiments, the mechanism underlying directional translational control of metallic nanowires on microfibers in line-contact configurations. Nanosecond pulsed laser excitation creates a spatiotemporal non-equilibrium regime where transient thermal shocks deliver temporal driving stress while the quasi-one-dimensional thermal profile spatially decouples competing force components. Axial temperature gradients break translational symmetry, transforming body forces into directional surface propulsion via rapid thermal expansion-contraction dynamics. This process overcomes interfacial friction, enabling nanometer-precision translation (palladium nanowires: 3.61 nm/pulse; gold nanowires: 2.73 nm/pulse), while lateral thermal symmetry suppresses transverse forces and maintains positional stability. The mechanism extends to metallic nanobelts and nanosheets, confirming broad applicability across morphologies. The coexistence of axial propulsion and lateral confinement arises from symmetry breaking along the axial direction and symmetry preservation in the lateral directions. These findings reveal a fundamental shift from rotational dynamics in point-contact to translational motion in line-contact, opening pathways for non-destructive assembly and intelligent sensing applications of nanodevices on solid interfaces.