Precision removal of uneven skin tissue at the micrometer level via focus-corrected femtosecond-laser ablation

From the perspective of aesthetic surgery and regenerative medicine, the precision of surgical instruments is critical for preventing aesthetic complications during procedures such as skin debridement and the removal of unwanted tissues, as well as for better regeneration. Femtosecond lasers (fs-lasers) can achieve micrometer-level tissue removal. However, an uneven skin texture can cause the laser to defocus, leading to iatrogenic injury and hindering clinical application. Overcoming the defocusing tendency of fs-lasers is therefore crucial for their clinical use.

Our self-developed fs-laser microfabrication platform was used to implement a focus-corrected method based on 2D interpolation for uneven skin surfaces, using different laser powers and velocities for linear, planar, and 3D scanning of porcine skin. Leveraging the identified dose–response relationship, the optimized device and parameters were used for precise tissue ablation in an in vivo rat experiment. The structural integrity and viability of the remaining skin were evaluated histologically.

Our study revealed that focus-corrected fs-laser ablation enabled controllable micrometer-level removal of target skin tissues. The depth of tissue removal was correlated with the fs-laser single-pulse energy. Unlike other laser devices, the scanning velocity did not affect the ablation depth, as the focusing mechanism of the focus-corrected fs-laser restricts ablation beyond the focal point. Appropriate fs-laser parameters for parallel linear scanning enabled tissue removal in various 3D shapes. Increased depth of field, increased single-pulse energy, and faster scanning velocity enabled precise, rapid, and safe ablation of skin tissue in the rat model. Histological and biochemical analyses demonstrated that focus-corrected fs-laser debridement did not damage the surrounding collagen structure or cell viability of the wound.

We demonstrated that focus-corrected fs-laser ablation enables micron-scale skin removal with minimal collateral damage. By selectively adjusting single-pulse energy for depth-specific ablation and operation at the maximum permissible scanning velocity, this technique enables precise skin removal in the desired shape, offering an innovative and ultrahigh-precision surgical approach for skin as well as other tissues or organ surgery.