There is a long history of attempts at
replicating neural systems either in software or in conventional
semiconductors, such as the FACETS project (not to
mention the creation of conventional logic gates from lab-grown
biological neurons!) According to a USC
Viterbi news release, researchers at the BioRC project, whose goal
is research on
an artificial cortex, have succeeded in creating a functioning synapse
from carbon nanotubes.
The new research was presented by Alice C.
Parker in the paper "A
biomimetic fabricated carbon nanotube synapse for prosthetic
applications" at the Life Science Systems and Applications Workshop
in April 2011. (unfortunately the actual paper is behind a paywall but
the abstract is readable). An earlier paper, "A Biomimetic Carbon
Nanotube Synapse Circuit", describes the proposed
design of synapse including schematics and comparison with biological
neural