Optimization of processing parameters and conditioning for efficient bone tissue ablation by femtosecond laser

Femtosecond laser processing is well known because of the achievable unparalleled precision with minimized thermal effects on most materials, making this technology competitive for its clinical use on living tissue. Nevertheless, femtosecond laser processing often requires an optimization of the parameters in order to increase the ablation rate which remains too limited compared to CW or QCW lasers. This study identifies an optimized set of process parameters (wavelength, temperature, bone hydration) for efficiently ablating bone tissue. Three different absorption regimes are studied using fs laser sources centered at wavelengths of 1030 nm, 515 nm and 343 nm. The thermal effects generated by the interaction of the fs laser and the bone were analyzed using a thermal camera and thermocouples with different cooling methods (water and air). Our results highlight (i) the significant capacity of the visible wavelength (515 nm) to ablate bone tissue with a maximum value of 0.66 mm³/s on pork femurs and that (ii) the use of water for cooling the sample is the most effective method of cooling and reduce thermal propagation without impacting the ablation rate. This study also raises awareness about the role of the anatomical region (femur, tibia, etc.) and species (pig, chicken, etc.) of the investigated bone tissue samples which may induce significant differences in ablation efficiency.