The memristor was originally envisioned in 1971 by circuit theorist Leon Chua as a missing non-linear passive two-terminal electrical component relating electric charge and magnetic flux linkage. More recently the memristor definition was generalized by Leon Chua to cover all forms of 2-terminal non-volatile memory devices based on resistance switching effects and Chua has claimed that the memristor is the oldest known circuit element with its effects predating the resistor, capacitor and inductor. The memristor is currently under development by various teams including Hewlett-Packard, SK Hynix, and HRL Laboratories.
When current flows in one direction through a memristor, the electrical resistance increases; and when current flows in the opposite direction, the resistance decreases. When the current is stopped, the memristor retains the last resistance that it had, and when the flow of charge starts again, the resistance of the circuit will be what it was when it was last active. It has a regime of operation with an approximately linear charge-resistance relationship as long as the time-integral of the current stays within certain bounds.
In 2008, a team at HP Labs announced the development of a switching memristor based on a thin film of titanium dioxide. These devices are being developed for application in nanoelectronic memories, computer logic, and neuromorphic computer architectures. In October 2011, the same team announced the commercial availability of memristor technology within 18 months, as a replacement for Flash, SSD, DRAM and SRAM. In March 2012, a team of researchers from HRL Laboratories and the University of Michigan announced the first functioning memristor array built on a CMOS chip for applications in neuromorphic computer architectures.