紫外皮秒激光辐照生物骨组织消融特性研究 (特邀)

Objective Ultrafast lasers are promising tools for medical applications, particularly in bone tumor therapy. However, the high hardness and brittleness of osseous tissue, together with its pronounced thermal sensitivity, make conventional surgical resection challenging, while photothermal ablation techniques often cause substantial and difficult-to-control collateral thermal injury. In this study, an ultraviolet picosecond laser was employed to investigate low-thermal-damage ablation strategies using porcine rib specimens, selected for their close structural similarity to human bone. Initial experiments focused on single-pass linear scanning ablation, and a three-dimensional numerical model was developed using the same process parameters. Comparison with experimental measurements confirmed good predictive agreement. Using the optimized laser parameters, microgrooves with an aspect ratio exceeding 5∶1 were fabricated with a markedly reduced heat-affected zone. The scanning trajectory was then iteratively refined via coupled simulation and experimental validation, enabling precise machining of a square cavity with a side length of 5 mm. No appreciable thermal damage was observed during these procedures, and the results exhibited good repeatability. Overall, this work provides a practical and validated basis for advancing ultrafast laser technologies in clinical and biomedical applications. Methods Single-line ablation trials were first carried out. The effects of picosecond ultraviolet laser parameters on ablation performance were systematically evaluated using single-factor and orthogonal experimental designs. The ablation depth and width, as well as the extent of the heat-affected zone (HAZ), were quantified by optical microscopy and extended depth-of-field microscopy. These measurements were used to elucidate parameter–response trends and to rank the relative contributions of individual process variables. In parallel, a numerical model describing the interaction between the picosecond ultraviolet laser and biological bone tissue was developed, and its predictions were validated against the experimental results. Three-dimensional ablation experiments were then conducted. Guided by the combined simulation and experimental outcomes, an optimized parameter set was identified and applied to fabricate square holes with depths exceeding 1 mm. The ablation quality of the fabricated structures was finally assessed using white-light interferometry. Results and Discussions Through single-factor and orthogonal experimental designs, the effects of laser parameters on ablation morphology were systematically investigated, and corresponding process parameters were optimized. This enabled the fabrication of micro-groove structures with an aspect ratio exceeding 5 and a heat-affected zone (HAZ) constrained to less than 20 μm. A strong concordance was observed between simulated and experimentally obtained ablation widths and depths (Fig.6). At varying scanning spacings, insufficient laser spot overlap resulted in discontinuous and poorly integrated line-by-line ablation, thereby undermining the structural integrity of the processed region. Conversely, excessive overlap induced pronounced heat accumulation, a marked increase in localized temperature, and an expansion of the HAZ (Fig.7). Experimental and simulation results demonstrated consistency in this respect (Fig.8). Utilizing the optimized parameters derived from the experiments, appropriate laser processing windows were identified for both wide-groove and hole-structure ablation (Fig.9). The ablated morphologies were characterized via optical microscopy and white-light interferometry. The fabricated square-hole structures exhibited high integrity, with depths surpassing 1 mm and no discernible indications of significant thermal damage (Fig.10). Conclusions Through single-line ablation tests using single-factor and orthogonal experimental designs, it was confirmed that laser power and scanning speed are the dominant factors governing the ablation depth/width and the heat-affected zone (HAZ). The optimal parameter set for single-line ablation was identified as laser power of 4 W, repetition rate of 300 kHz, scanning velocity of 300 mm/s, providing a stable process baseline for subsequent 3D-structure fabrication. Under the above parameters, ablation simulations and experiments with different numbers of scanning passes exhibited good agreement in the evolution trend of ablation morphology, indicating that the established 3D model has effective predictive capability. Meanwhile, limiting the number of passes to no more than 10 can significantly suppress heat accumulation and the growth of thermal damage. For 3D structure construction, the scanning spacing plays a decisive role in balancing surface flatness and thermal accumulation: an excessively large spacing leads to poor inter-track fusion, whereas an overly small spacing results in temperature rise and HAZ expansion. Based on combined simulation and experimental results, 20 μm was determined to be the optimal scanning spacing, enabling continuous wide-groove ablation with a relatively flat bottom surface. Using the optimized parameters and toolpath, a square cavity with a side length of 5 mm and a depth of >1 mm was successfully fabricated, showing intact morphology and good surface quality with no obvious thermal damage. These results validate the repeatability and medical/clinical applicability of the proposed “simulation–experiment coupled optimization” strategy for precision ablation of bone tissue.