Here's the original article with all the scientific data. The fixtures appear to be made of titanium, which is nothing too special in the medical world, it does not require any external large batteries, and has actually been used for 3 full years, still using it today.
Also here's the pics again but with the full scientific context added as alt text
https://www.science.org/doi/10.1126/scirobotics.adf7360@@#
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