Nyle Steiner, of the Spark Bang Buzz blog has been at it again, demonstrating cool electrical/electronic devices that are homebrewed. This time he constructed his own memristor.
If you aren't up on electronics, you might not have heard of memristors before. While Leon Chua proposed that such a circuit element was possible, they weren't actually created in a lab until 2008. But what is a memristor? It's a circuit element whose resistance depends on the sum of the charge flowing through it. In other words, if you pass a voltage through a memristor in one direction, it's resistance increases. If you pass a voltage through the other way, it decreases. But if you stop the voltage entirely, the memristor "remembers" the previous value it had, and will keep the same resistance it had when the charge was cut.
Amazingly, Nyle Steiner observed this memory effect in some brass shell casings which had been oxidized in a sulfur environment (I'm no chemist, so I won't try to explain that part) over 10 years ago. He made this short video demonstrating such a memristor using both a curve tracer (which may take a few minutes of though to understand exactly what is going on) but also through a very basic circuit demonstrating how the memristor can "remember" a single bit and turn an LED on and off. If you didn't know that memristor's existed, you'd probably be forced to try to explain the behavior of the circuit in terms of capacitance: but unlike capacitance, the memristor doesn't need to be refreshed to maintain its state. You'd find it rather puzzling, to be sure.