 Nobody has yet attempted to implement this thought experiment; some types of biological enzymes and enzyme complexes (especially ribosomes) function chemically in a way close to Feynman's vision.Feynman also mentioned in his lecture that it might be better eventually to use glass or plastic because their greater uniformity would avoid problems in the very small scale (metals and crystals are separated into domains where the lattice structure prevails).This could be a good reason to make machines and electronics out of glass and plastic.