Also, Arthur C Clark wrote in "Rendezvous with Rama" that ETs could be "biots", or biological robots.
https://www.yahoo.com/news/aliens-actually-immortal-robots-theyre-billions-years-old-researcher-claims-090206399.html https://www.yahoo.com/news/aliens-actually-immortal-robots-theyre-billions-years-old-researcher-claims-090206399.html
