Sugru is the brand name of a type of silicone rubber that sets on contact with air. It was commonly thought to be an excellent bioproofing material, however upon being tested the results were "Sugru is so bad, there isn't even a metric to describe how bad it is. Things like this are not fit to be put in the body".
"SFM tested it alongside TiN, Parylene, and some other materials and it broke up so easily that it couldn't so much as be tested by some methods. It also showed tons of fouling." (Cassox)
Do not attempt to use Sugru as a bioproofing material.