# Overview on the Evolution of Laser Welding of Vascular and Nervous Tissues
## 2 Laser Welding of Vascular and Nervous Tissues
### Welding Parameters and Bonding Conditions
[51] presented a different surgical approach, which is shown in Figure 6. This strategy consists of the insertion of a laser fiber implemented in a balloon catheter, allowing a 360\({}^{\circ}\) laser irradiation over a two-layer soldering procedure. Eleven successful welds in fourteen executed were reported by these authors. In turn, [PERSON] et al. [49] also reported that a laser fiber that delivers a 360\({}^{\circ}\) laser irradiation can also diminish the thermal damage. As described above, important progress has been registered in laser welding of nervous and vascular tissues. Therefore, the development of fiber lasers is of great importance to the laser-welding technique, mostly due to their advantages, such as excellent heat dissipation, beam quality, and efficiency [79; 80]. Because of their diversified operating modes, wavelengths, and energy levels, different fiber lasers, such as erbium-, thulium-, holmium-, and ytterbium-doped families, can be used, for example, in microsurgeries of soft tissues [80; 81]. The effect of these lasers in soft tissues can range from ablative purposes to regenerative procedures like laser welding [82]. In terms of medical applications, various studies have proven their suitability for photodynamic therapies, biomedical sensing, as well as for other procedures in the vascular and dentistry fields [81; 83; 84]. Although laser-welding improvements have been achieved with solder solutions, laser-activated dyes, intraluminal devices with 360\({}^{\circ}\) laser irradiation, etc., inherent thermal damage is still present. As an alternative to thermal laser welding, photochemical tissue bonding (PTB) does not inflict any thermal  
Figure 6: Schematics of the laser-assisted vessel soldering [51]. damage to the welded and surrounding tissues. With this technique, sealing of tissue is achieved through the use of dyes that are chemically activated, such as Rose Bengal (RB) dye and Riboflavin-5-Phosphate, allowing the formation of fiber cross-linking bindings [53; 54]. Results showed no operative and post-operative bleeding, absence of aneurysms, and high tensile strength [40; 49; 52; 54; 58]. Moreover, electrosurgical high-frequency (ESHF) technology has already been tested as an alternative technique to laser photothermal and photochemical mechanisms. [PERSON] and [PERSON] [55] presented an animal study in which peripheral nerve repairs were made by welding soft tissues with high-frequency current. A similar morphology was achieved in sutured and high-frequency (HF)-welded nerves, with beneficial effects of ESHF welding in terms of the regeneration process. It should also be noted that new research directions are starting to emerge within these surgical practices. Auxiliary technological devices and instrumentation, such as robotic-assisted surgeries with enhanced image-processing systems [85; 86; 87], as well as the development of new biomaterials based on nanotechnology [88; 89], show a great potential for driving the future evolution of reconstructive vascular and nervous laser welding.