Femtosecond laser-induced transfer effectively prints plasmonic nanomaterials onto stretchable substrates. The transfer behaviors are precisely adjusted through laser fluence, distinguishing femtosecond laser processing from melt-driven or vapor-driven transfer processes. Since this transfer typically occurs at the nanoscale, elucidating its mechanism requires visualization with high spatiotemporal resolution. In this study, pulsed lasers are integrated with a transmission electron microscope for nanosecond- and nanometer-scale observations of transfer behaviors. The thermal stress wave-driven transfer regime is revealed through a two-temperature model coupled with molecular dynamics simulations. The irradiated nanoisland detaches and jumps away from the supporting substrate within tens of picoseconds, while its complete melting and contraction into spherical nanoparticles occur over several to tens of nanoseconds, marking the first nanoscale confirmation via experimental observation and atomic simulation. Ultrafast laser heating induces inhomogeneous lattice expansion, generating a gigapascal-level compressive thermal stress wave that propagates at the speed of sound. Upon reaching the interface, the compressive stress wave reflects as a tensile wave, leading to the detachment of nanoislands from the substrate. The process is primarily governed by directionally propagating normal stress waves rather than static thermal shear stress, with ultrafast non-equilibrium heating and constraints from the rigid substrate as crucial factors. This study reveals a novel thermal stress wave-driven regime in femtosecond laser-induced nanomaterials transfer, offering an effective approach for fabricating nano-plasmonic devices. These insights into thermo-mechanical coupling carry significant implications for advancing broader femtosecond laser micro/nano-processing.
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