The ablation experiments were carried out in a customized ultrafast laser machining setup as shown in Fig. 1. A detailed description of this setup can be found in previous publications24,26 and is briefly depicted here. Femtosecond laser pulses from a Ti:Sapphire oscillator (Tsunami, Spectra Physics) were amplified to maximum pulse energy of to 500 μJ and pulse duration of 170 fs at a repetition rate of 1 kHz. For the results reported here, the wavelength of the laser was set at 800 nm. The collimated beam diameter was reduced to a final diameter of 4.4 mm through a telescope. The combination of a polarizer and a half-wave plate was used to adjust the pulse energy. The laser exposure time (i.e., number of pulses used in ablation) was adjusted by a computer-controlled mechanical shutter (VS25S2S1, Uniblitz, Rochester, New York). A plano-convex lens (, BK7, Thorlabs, Newton, New Jersey) focused the collimated beam down to a spot size diameter of 30.2 μm. The bone sample was placed in a sealed glass vial during ablation to prevent the biological residue from spreading outside the environment. A glass microscope coverslip was used to seal the vial while allowing the ablation beam to pass through. Horizontal scanning of the sample is achieved using an translational stage (UTM100PP.1, Newport, Irvine, California), while vertical scanning is achieved by moving the focusing lens through a linear () translation stage (MFN25PP, Newport).