Research teams replicated a biological synapse by using gold nanoparticles along with an insulation layer and an organic semiconductor transistor made of pentacene. Voltage spikes similar to neurotransmitters were imitated by using pulsed voltages. The researchers could even adjust the time delay for each spike.
Now, I read this on Popular Science, which culled the details from Physicsworld.com. I thought about doing more detailed research there, but the PopSci piece made my brain hurt enough, especially when they mentioned that there are probably 100 billion neurons, which have about 10,000 times that number of synapses.
These researchers have a goal of creating a "wet" computer, one based on a chemical version of neurons. While that may be a long way off, still, it's not just a room full of bulky computers replicating a cat or mouse brain. We've come a long way from the first transistor back in 1947. We're getting closer and closer to Blade Runner territory.