This is a finger that is designed to be operated by the pull of a string that goes through the links.
This design is untested, so if anyone prints this please let me know if it works/ doesn't work, what to change/ what to keep
This finger features printed springs so no extra hardware is required other than pins/screws/bolts (of your choice) to go into the hinge part. you could also design these and 3d print them.
this is V3 of this design