Computers go beyond electronics. About 50 years ago, there was even excited talk of “fluidic” computers which used the Coanda effect (the tendency of a fluid jet to stay attached to a convex surface). They employed water or air in plastic channels to implement logic gates; the gates were interconnected by standard, flexible plastic tubing (References 1 and 2).
The advantage was their noise immunity, but their size and physical awkwardness was among their many negatives. A typical four-input AND or OR gate alone was about half the size of a deck of cards. Air-based fluid computing is still a research topic using etched microchannels (not to be confused with the widely used fluidic microchannels of medical instrumentation), but let’s face it – it’s tough to compete with the realities of Moore’s “Law.”
The days of analog computing are pretty much gone, although there are holdouts and even some research is still being done (see Reference 3).