Storing Data with a Flash of Light

These days, just a handful of memory technologies are used in virtually all computer systems. Sure, there are lots of variations out there, but the basic technologies are closely related. In the early days of computing, the landscape was much more diverse while engineers and researchers sought out the most efficient and performant designs. You might see memory systems made up of electromechanical switches, electron tubes, magnetic drums, mercury delay lines, and other exotic components at that time.

As artificial intelligence and other cutting-edge applications continue to push the limits of what is possible with present computing hardware, researchers are once again ramping up experimentation into alternative memory technologies. The low power consumption, fast switching speeds, and scalability of memristors, in particular, is making them a hot topic in high performance computing research lately. This made YouTuber Marb's lab want to experiment with this interesting technology.

While exploring the topic, Marb's lab realized that the definition of a memristor is fairly loose, and some very unconventional methods might be used to construct them. So to learn more about the technology, and explore what is possible to achieve with it, Marb's lab constructed a novel memristor from an unlikely substance — a bistable photochromic dye. Using this dye, an analog, non-volatile memory device controlled by laser light was demonstrated.

To build the memristor, a photochromic dye called 1,2-bis(2,4,5-trimethyl-3-thienyl)-cis-1,2-dicyanoethene, or CMTE, was mixed with pure isopropanol and toluene. This mixture was then stirred into a slow-curing resin before being poured into a quartz glass cuvette where it cured for 72 hours. When this resin block was irradiated with a 405nm laser, it changed its color, effectively writing data to it. Even after being kept in darkness for multiple days, the color change was still present. Blasting the memristor again, but with a 532nm laser, reverses the effect, essentially erasing the memory.

With the core of the memory device tested, a 3D-printed case was designed to protect the dye from ambient light that could alter its state unintentionally. Both lasers were placed in the case, as was a VEML7700 light sensor, which was used to read out the memristor’s present state. The lasers and the light sensor were hooked up to an Arduino Nano microcontroller development board to handle writing, clearing, and reading the state of the memory device.

Needless to say, this solution is large, consumes a lot of energy, and is slow — it will not be powering the supercomputers of tomorrow. But the project is a good crash course on memristor technology, and also a reminder to think outside of the box. Technological advances are only possible when we try something that has not been done before.