Low temperature solder for laser tissue welding

In this study, a two layer (TL) solid solder was developed with a fixed thickness to minimize the difference in temperature across the solder (ΔT) and to weld at low temperature. Solder strips comprising two layers (65% albumin, 35% water) were welded onto rectangular sections of dog small intestine by a diode laser (λ=808 nm). The laser delivered a power of 170 ± 10 mW through an optical fiber (spot size ∼ 1 mm) for 100 seconds. A solder layer incorporated also a dye (carbon black, 0.25%) to absorb the laser radiation. A thermocouple and an infrared thermometer system recorded the temperatures at the tissue interface and at the external solder surface, during welding. The repaired tissue was tested for tensile strength by a calibrated tensiometer. The TL strips were able to minimize ΔT (12 ± 4°C) and control the temperature at tissue-interface. The strips fused on tissue at 55≤T≤62°C had higher tensile strength than the strips soldered at 51≤T<55°C (19.1±6.6 versus 13.1±6.4 gmf). The solid solder could efficiently weld at 60°C as it became insoluble and formed stable bonds with tissue. Fluid albumin solders, by contrast, requires temperatures ≥70°C for tissue repair, which cause more irreversible thermal damage.