Professor Leon Chua, the originator of the term memristor for a variable resistance device with pinched hysteresis behavior, has joined forces with Professor Christofer Toumazou and Themistoklis Prodromakis, both of Imperial College London, to demonstrate that the behavior has been observed for more than 200 years.
Chua originally postulated the existence of a fourth fundamental passive electronic circuit element as a consequence of electrical theory and coined the term memristor in 1971. Hewlett Packard Co. picked up use of the terminology and produced an electronic circuit element based on titanium oxide in 2008.
In fact such variable resistance systems can be based on a wide variety of physical systems including movement of mobile ions or oxygen vacancies, the formation and rupture of conductive filaments and phase changes in materials.
In their paper Prodromakis, Toumazou and Chua examine some of the earliest and most fundamental experiments in electricity and find evidence of memristor behavior in a variety of studies, including those of the electric arc by Hertha Ayrton and of thermistors by Michael Faraday. The oldest they touch on are those of Sir Humphry Davy, inventor of the electric arc and Faraday's mentor, who performed experiments using voltaic piles in 1808 and subsequent years.
The conclusion is that the memristor is not an invention but a description of a natural phenomenon that can be found in many dissipative devices made from many materials, internal structures and architectures. It adds that observation of memristor behavior just happens to be older than the first formal discussions of the resistor (Ohm in 1827) and the inductor (Faraday in 1831).
memristor behaviour is NOT non-linear - it's time-dependent. That can look non-linear, but when Chua went looking for the 'fourth device' he knew he was looking for a device in which the resistance depends on the time-integral of the current through it (in effect the resistance is directly and linearly proportional to the total charge that has been transferred over the device's history. That is the essence of the device that Chua defined
What Chua and others are calling "memristor" behavior is representative of a wide variety of dynamic systems and does not necessarily have anything to with the memristor as originally defined in 1971 or as redefined by Chua in 2011. What Chua and HP are doing with the "memristor" has a lot more to do with enhancing their reputation than proper science or ReRAM research. I refer you to a presentation I gave at ISCAS 2010 and a paper I wrote responding to Stan Williams of HP for more details.
Why is this so controversial? Memristor behavior is nonlinear, and it's no surprise that first measurements showed all kinds of nonlinearities. Electric arcs are inherently non-linear, and if they can show and justify a memory-driven behavior, their thesis would make a lot of sense. At this point I am not convinced, but I simply do not see shenanigans that the others seem to imply.
The text currently reads "It adds that observation of memristor behavior just happens to be older than the first formal discussions of the resistor (Ohm in 1827) and the inductor (Faraday in 1931)." 1831 for Faraday surely.
The funniest part of the article is the conclusion:
"We end this historical narrative by noting that even though the memristor has seen its light of joy only recently in 2008, and has been recognized as the fourth circuit element along with the resistor, capacitor and inductor, it actually predates the resistor, which was formally published by Ohm in 1827, and the inductor, which was formally published by Faraday in 1831."
For those who do not see how delusional and revisionist this statement is you are missing a really good joke.
For a more objective insight into the history of Ohm's Law I would recommend the following text:
Schiffer, Michael (2008). Power Struggles: Scientific Authority and the Creation of Practical Electricity Before Edison. MIT Press
Chua seems to me more a figure like Peter Barlow, a mathematician who, prior to Ohm, proposed a law describing the conduction of wires based on pure reasoning rather than experiment. Barlow was eventually discredited by experiments.
I always felt HP was the one guilty of overselling its memristor, but Chua fell into the temptation of generalizing to all resistance memories. I think at most a special subset would fit being memristors.
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