Hi Ashoorirad, I do not think PCB is bio-compatible enough to be implanted directly. From my understanding of electronics, PCB fabrication involves the use of fiberglass epoxy resin with a copper foil besides PCB goes through lot of chemical treatment none of these methods were for bio-implant friendly. Flexible electronics are on another avenue u could focus on, designing flexible implant using a biocompatibile polymer matrix and use circuit connections fabricated from biologically non reactive materials (conductive carbon inks, silver or gold) could be bit more logical. Hope this helps, Best.

Dear Berwin, Thank you so much for your useful comment.