I've never been convinced that the memristor is worthwhile to consider as a "fundamental passive device" as everyone seems to want to claim. There are a few rea

I've never been convinced that the memristor is worthwhile to consider as a "fundamental passive device" as everyone seems to want to claim. There are a few reasons for this: (1) It's underspecified compared to the fundamental passive circuit elements. For linear R, L, and C, each has one parameter, its value. Ignoring trivial cases (viz., resistors), a memristor has as its memristance an arbitrary function of V and I. As a result, any interesting memristor is automatically not LTI. (2) It's not particularly special. Why don't we also define a memcaptor, whose capacitance is a function of its current history? I could easily do this, for example, by making a capacitor where one plate is attached by a spring to a fixed support; then, by adding charge, I move the plate and increase the capacitance (or, by removing, I decrease it). Oh wait, that's just a nonlinear capacitor. In the same way, the memristor is just a funny name for a particular kind of nonlinear resistor. (3) It's not particularly practical (for the moment). It can't be made in anything but a very specialized, presumably extremely expensive process. I hope this changes---I'm sure it'll encourage someone to use them!---but at the moment this really limits my excitement. (4) There's nothing I can build with a memristor that I couldn't build already. This isn't like the invention of the vacuum tube: you give me a memristance function, and I can build you a pseudo-memristor out of transistors, Rs, Ls, and Cs. Yes, it could be less {space,power,?} efficient, but this is not a quantum leap in technology the way the vacuum tube was (one could not, with 1890s technology, reasonably build something that emulates a vacuum tube). I'll admit that strictly interpreting my last argument, the vacuum tube could be made to emulate a transistor and thus the transistor wouldn't count as a quantum leap---clearly ridiculous. However, I'd contend that the real value of the transistor was only evident once it was sufficiently miniaturized and its production was sufficiently cheap. You show me memristors that are six orders of magnitude cheaper than transistors and by golly I'll be a convert. Even then, it'll just be yet another nonlinear device with which we can do interesting things---and just like the transistor, the memristor will simply never be as fundamental as R, L, or C.