Minimally invasive surgery (MIS) robots, such as single-arm stapling robots, are key to oral and maxillofacial surgery because they overcome space constraints in the oral cavity and deep throat. However, biodegradable suture staples should be developed for the single-arm stapling robots to avoid a secondary operation. For this aim, a new type of Mg-3Zn-0.2Ca-2Ag biodegradable alloy wire was developed in this study applied as suture staples. Its tensile strength, yield strength, and elongation are 326.1 MPa, 314.5 MPa, and 19.6%, respectively. Especially, the alloy wire attains the highest yield strength value reported among all the biodegradable Mg wires, which is mainly attributed to fine grain strengthening and second phase strengthening such as Mg2Zn11 nano phase strengthening. Moreover, the corrosion rate of this alloy wire in simulated body fluid (SBF) reaches 26.8 mm/y, the highest value among all the biodegradable Mg alloy wires reported so far, which is mainly from the intensified galvanic corrosion between the Ag17Mg54 phase and the Mg matrix. In vitro studies demonstrate that the alloy wire exhibits good blood compatibility and low cytotoxicity. The cone beam computed tomography (CBCT) data shows that the suture staple made of the Mg alloy wire provides better mechanical support in the early postoperative period. From the single arm robot tests, it confirms that suture staples can close the wound tightly and remain stable over time. This research provides a good material selection for the automated suturing in oral and throat surgery robots.
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Open Access
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Inferior absolute strength and dissolution properties are the main bottlenecks for the widespread application of dissolvable magnesium alloys in complex working environments for unconventional oil and gas resources. Here, a novel functional peak-aged Mg-9.5Gd-2.7Y-0.9Zn-0.8Cu-0.4Ni (wt.%) alloy for fracturing tools is reported, and it possesses an ultimate tensile strength of 457.6 MPa, ultimate compressive strength of 620.7 MPa and dissolution rate of ~43.7 mg·cm−2·h−1 in 3 wt.% KCl solutions at 93 ℃. The excellent strength of the aged-alloy is primarily attributed to the combination of grain refinement, long-period stacking ordered (LPSO) strengthening, and precipitation strengthening induced by stacking fault and β’ phase, among which the precipitation strengthening is dominant. Further investigations confirm that the corrosion is triggered from the micro-galvanic coupling between the Mg matrix and the cathodic lamellar and block LPSO phases. Strip-shaped corrosion pits along with LPSO phases are subsequently formed, significantly accelerating corrosion. The β’ precipitates can effectively improve the strength without compromising the dissolution rate because of their nanoscale size. This study provides an excellent material selection for dissolvable fracturing tools and presents a strategy by which a synergistic combination of strength and dissolution rate is achieved via peak-aging treatment.
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