Once a upon a time a little before grunge and and a little after new wave I made a $1 bet with a colleague that:
"a solid state electronic technology was available in the 19th century that could be used to build useful digital logic circuits."
The nexus of the bet and the discussion that preceded it was some beefing on my part about having to buy qualified and tested integrated circuits made from silicon in special factories. Wouldn't it be great if we could skip the silicon foundry and build, test and qualify our own circuits from more readily available raw materials. My colleagues reply was "if it was possible somebody would have done it already." I hate that answer I always have and I always will (at least I hope so). So, I bet my colleague $1 that there was such a technology.
My colleague (long since former colleague) is doing well doing other stuff and has no remembrance of this wager, oh well. . .It took about five years of researching old books, hiking up some interesting blind alleys and of course building circuits to discover one that worked shown below:
Edward P. Vogel, "Tic Tac Toe Game Using An Optically Routed Gate Array" Proc. SPIE 2863, 407 (1996); doi:10.1117/12.256247:
Notice the "1996", my work has been on hiatus for too long. Recently I discovered that a certain type of synchronous logic circuit could be constructed using only NOR gates and my interest and enthusiasm for building "useful circuits" has been renewed.