Definition: memristor

(MEMory ResISTOR) A non-volatile memory technology that can change its resistance in varying levels. It can offer resistance in two states for a digital 0 or 1 or to levels in between to go beyond a binary system.

In 2008, HP demonstrated a memristor comprising a cell made of two layers of titanium dioxide. One layer is conductive because it is missing a few oxygen atoms. When a positive charge is applied to the layer with the missing atoms, the vacancies are pushed into the other layer, making it conductive as well and changing its resistance. The more the cell is charged, the lower its resistance. Negative charges reverse the effect.

Very Fast and High Density
Two distinct advantages of memristors are that moving the vacancies between the adjacent levels can be done much faster than other known switching methods, and the cell density approaches that of hard disks. Theorized by Leon Chua in the early 1970s, and if commercially viable, memristors may replace flash memory and dynamic RAM (DRAM) in the future. See future memory chips and RRAM.