Finite element simulation of photothermal-mechanical response of skin tissue induced by the non-ablative fractional laser irradiation.

To understand the mechanism of non-ablative fractional laser, a photothermal-mechanical response model of skin was established, revealing microthermal damage depths of 400, 1000, and 250 μm for 1440, 1550, and 1927 nm lasers, respectively. The optimal ratios of spot radius to microbeam spacing are identified: <0.088 (1440 nm), <0.105 (1550 nm), and <0.070 (1927 nm). These ratios maximize safety by restricting the temperature rise in normal tissue, with maximum stress (2.9 kPa) far below rupture thresholds. The mechanical impact range is broader than the thermal one, signifying that the areas experiencing thermal pain are larger than the coagulation zones.