## 2 Materials and Methods  
The reactive multilayers used in this work were freestanding Ni/Al Nanofoil(r) (Indium Corporation, Clinton, NY, USA) layers with a bilayer thickness of 50 nm and an overall thickness of 40 \(\upmu\)m. According to the manufacturer's specifications, these multilayers have an atomic ratio of 1:1, enabling fast heating of the multilayers up to 1350-1500 \({}^{\circ}\)C with reaction front velocities of 6 to 8 m/s. The multilayers are coated on both sides with a 1 \(\upmu\)m thick layer of InCuSil(tm) (61.5 wt.% Ag, 24 wt.% Cu, and 14.5 wt.% In). For the laser structuring experiments, samples 10 mm in height and 15 mm in width were mounted on a 2-axis, computer-controlled stage in ambient atmosphere. To prevent redeposition of the ablated material, the surrounding area was evacuated by means of a vacuum dust collection system. Two Ti:Sapphire lasers generating femtosecond (fs) pulses with a gaussian beam shape from Spectra-Physics (Santa Clara, CA, USA) were used to structure the RMFs. The first one was a Spifire laser with 100 fs of pulse duration at full width half maximum (FWHM), and the second laser used was a Solstice(r) ACE(tm) with 150 fs of pulse duration at FWHM. The optical configuration involved directing the pulses from both lasers through an aspheric lens with a focal length of 26 mm, resulting in a spot size of approximately 45 \(\upmu\)m when focused. The number of pulses was chosen to ensure that the fluences used to cut through the foil remained significantly well below the ignition threshold. The scanning speed was 0.03 mm/s and was kept constant for all samples. The specifications and parameters used for each laser are shown in Table 1. After laser irradiation, a few samples were additionally treated by immersion in ethanol in an ultrasonic bath for 1 h to remove process-induced oxide on the structured surfaces. A confocal laser scanning microscope (LEXT OLS4100, Olympus, Shinjuku, Tokyo, JP) in the optical mode and a scanning electron microscope/focused ion beam (FIB/SEM) instrument (Helios G4 PFIB CXe, Thermo Fisher, Waltham, MA, USA) were used to image the surface. The latter was also used for preparing FIB cross sections of the debris from the DLW process with a Xe ion beam and for qualitative chemical analysis with energy dispersive X-ray spectroscopy (EDS) with a third-party detector (Octane Elite Super, EDAX, Unterschleissheim, Germany). Cross sectional samples of the laser cut edge for transmission electron microscopy (TEM) were prepared in another FIB/SEM instrument (Helios Nanolab600, FEI, Hillsboro, OR, USA) with a Ga ion beam and an in situ micromanipulator. Final thinning of the samples was performed using a reduced ion beam with a high voltage of 2 kV. Transmission images were taken using a built-in detector for scanning transmission electron microscopy (STEM) at 30 kV. To avoid confusion with STEM in TEM, these images will be denoted as STEM-in-SEM images in the further text. TEM samples were investigated using two different instruments. In the first step, a conventional microscope with a LaB\({}_{6}\) source (JEOL 2011, JEOL LTd., Akishima, Japan) was used for imaging and selected area diffraction (SAD) in an attempt to obtain structural information. After that, further investigations were carried out in an aberration-corrected (S)TEM (JEOL ARM200, JEOL Ltd., Akishima, Japan, with CEOS corrector, CEOS GmbH, Heidelberg, Germany) with a cold field emission gun, high-angle annular dark-field (HAADF) and bright-field (BF) detector, and electron energy loss spectroscopy (EELS, Gatan Inc., Pleasanton, CA, USA) to supplement the SAD results with compositional information. The EELS mapping was carried out with a collecting semi-angle of 120 mrad, a dispersion of