The four passive components of electronics are the resistor, capacitor, inductor and the memristor, which was discovered only a few months ago.

Memristors (from memory-resistors, geddit?) are resistors whose resistance depends on their past. In that sense they remember the past or, as an electronics engineer might put it, they store information.

So new are memristors that nobody has had much time to think about what they might be useful for. That’s changing quickly.

A couple of months back we saw how they could be used to make neural nets that mimic the “intelligent” behaviour of slime mould.

Now Tom Driscoll and buddies at the University of California, San Diego have shown how memristors could work as low cost, high density memory.

It turns out that a thin film of vanadium oxide acts like a memrister when a current is passed through it. At a certain critical temperature, the current triggers a phase change in the film, turning it from an insulator to a metal-like conductor. And that significantly changes it’s resistance in a way that can be measured for hours afterwards. In effect, the resistor stores a singe bit of information.

Driscoll calls it resistive random access memory or RRAM, in which information is stored in the form of material resistance, which can be changed by an applied voltage .

Other substances, such as titanium oxide, also display similar memristive behaviour which could be adpated for memory related applications. And work is on going to characterise these.

Expect to hear a lot more about them this year.

Ref: arxiv.org/abs/0901.0899: Phase-Transition Driven Memristive System