The device with brains [Electronics Memristors]

The fourth basic element in electronics, the memristor promises a lot. But is it living up to expectations? Memristors represent a new class of nanoscale passive device characterised by a resistance that depends on factors such as the magnitude and polarity of the voltage applied or, in the case of spintronics, the degree of magnetisation. Turn off the voltage or the magnetising source and the memristor remembers its most recent resistance without any source of power until you turn it on again. Some research devices have held their values for at least three years.