MEMRISTOR - THE GHOST IN THE MACHINE

Ever thought about a computer with a RAM that does not lose all the data as soon as the power is turned off. Well now you can, with HP's groundbreaking discovery of this new technology that is known as memristor. 


Memristor is an abbreviation of “memory resistor” and yes this is what its job is – to remember its own history. To define a memristor “A memristor is a two terminal circuit element whose resistance depends on the magnitude and polarity of the voltage and the time period for which the voltage is applied to it.” A memristor has the ability to remember its most recent history when the power is turned off until the time it is turned on again, be it a day or a year later, it will be the exact same information that the device held at the time it was turned off.

To make it simple consider a situation where you just take the battery out of your laptop right now, put it back and start it, what do you think will happen??  Well first of all you will lose all of your unsaved work. Talking about your laptop, it will start with a message that prompts you to tell the machine whether to just start it in a simple fashion or safe mode. Then the machine starts loading all the files again, checking for errors caused due to the sudden shut down and recovering from those failures. In some cases this may take like forever.

Now let’s consider a laptop with memristors in it. When the same experiment is performed on this laptop and it is turned on again, it starts from the same point where you left it. You will not lose any unsaved work. There is no loading of files, no auto recovery and the reason is simple, it does not need a power supply to remember its state, it just remembers its history. You can take out the battery and leave your system for years and then start it again, it will start from the same point where you left it.

Technically a memristor remembers its most recent resistance. Memristors have the ability to alter resistance depending upon the voltage and the polarity of this voltage. You can think of a memristor like a pipe through which the water flows, the diameter of the pipe is the resistance and the water is the electric charge. Generally resistors have a fixed diameter. But in case of a memristor the diameter of the pipe can vary with the amount of water and the direction of water.  Now when the water flows from the top of the pipe, the pipe has some certain diameter. But when we change the direction of the flow of water the diameter of the pipe changes. Moreover the memristor have the ability to remember their diameter when the water last went through. If you stop the water flow, the diameter remains constant until the flow is turned on again.

It is also assumed that memristors can help us in simulating the functions of a brain, imitate the networks of neurons and synapses. This is because memristor can be made really small and can function as synapses. Thus in a near future we might have computers that can recognize patterns in the way human beings can, sounds to me like terminator stuff!! Well seems like this is the future of computers.

  

IS THAT ALL TO IT?

Actually it is just the beginning. It all started in 1971, when Leon O. Chua presented a paper “Memristor – The Missing Circuit Element”. What he said was that the memristor is a new two terminal circuit element and is characterized by a relationship between charge and flux linkage. Chua found a missing link in the pairing of the four circuit quantities – charge, current, voltage and magnetic flux. Out of the six possible combinations of these four variables, five have led to well-known relationships –capacitors connect voltage and charge, resistors connect voltage and current and inductors connect flux and current. The only relationship that was undefined was the one between charge and flux linkage.

And what made it the fourth fundamental circuit element was the fact that the behavior a memristor exhibits could not be formed by combining any of the three fundamental elements – capacitor, resistor and inductor. He advocated that memristor has properties that cannot be realized with RLC circuits alone.

And like every brilliant idea this too didn’t received any attention because the electronics industry was dominant with linear circuits at that time and for another 35 years after that.

SO HOW COME IT GOT DISCOVERED JUST LIKE THAT?

Well the story to that starts with R. Stanley Williams who is a research scientist in the field of nanotechnology. He joined HP labs in 1995 and is the founder of the Quantum Science Research Laboratory at HP. He was recruited to start a fundamental research group proposed by David Packard. Initially the research started with Moore’s Law. But science had something else in its terminals.

a simple cross-bar switch

Just like everything else (mostly) this was also an accident, in this case it was crossbar switches that led to it. What the team was trying to do involved a nanometer scale version of crossbar switches that besides switches for signals can act as bit memories if they are small enough. Now to define crossbar switches and their need we can say that they are like a set of perpendicular wires in horizontal and vertical directions and at every point where the wires cross a switch is located. This is what a cross bar switch is. Now what it is used for is actually more fascinating. Well these switches work on electrical charges. What that means is that an open switch mean 0 and a closed switch means 1. Now when charges are applied to the switch we can see a change in the switch orientation from 0 to 1 (means that the switch is closed now) or vice-versa, and with a small charge we can identify the orientation of these switches and read the data.

As you might have noticed that this is some kind of memory structure that it actually is, but we have many memory structures, don’t we… what’s so good about this one then. Well with this one in particular you can carry the Library of Congress on a thumb drive, and that is like a lot of space, a lot. Think about terabytes in a square centimeter of space. You can consider a drive with almost no space restrictions, what I mean is that you won’t have to worry about managing space on your drives anymore.

To cut the story short, they created many variants of them, some worked but not enough for technological applications, others didn't worked at all, and some produced really weird results. The problem was that when the device worked it was better than expected. They had discovered a device whose resistance can remain stable for years. But the success and failure were not because of the same factors. You can say that it was sometimes failing for the same conditions that it worked for earlier.

It was late 2002 now and the research was hanging in the middle of something that was still unclear. Things were getting insane at the labs because they had something that worked great but they had no idea of why it was working and how to model its working.

This is when memristor entered the game. The team got hold of Chua’s paper on memristor and to their surprise their device had similar results and graphs as were illustrated in Chua’s paper. And when they ripped their project open they found that it was not what they had created or intended to create, they had developed a memristor by mistake. And this was the reason why they were getting weird outputs. They were performing the experiment in the wrong way with a different estimate of the output than what was generated.

I hope this all comes to the market as soon as possible because I am tired of turning my laptop off and then turning it on and waiting for it to boot and all that. Plus the idea of removing your battery and keeping it without the battery and still I get all my last session’s work just like that sounds amazing. I hope this article was of some help to you all. Your suggestions are always welcome and thanks for reading. God bless you all.