blog

I previously discussed plastic electronics — and how molecules and polymers can be electrically conductive.

A key idea to remember is the unbelievable scale of molecules. If I used a conducting polymer molecule ~10 nanometers in length (as an example) and formed a conducting film approx. 1cm x 1cm in size, then to get one electron from one edge of the film to the opposite side, the electron would pass through on the order of 1 million molecules. (More likely, it would pass through far, far more. One million would require all the molecules to be lined up exactly and the electron to pass in a straight line.)

This rough concept illustrates that while polymer electronics are composed of individual polymer molecules, typical devices would be formed from vast numbers of molecules.

To get some idea of scale, people often refer to the famous Powers of Ten film, which includes examples of 10 nm and 1 nm chemical objects.

Of course basic science frequently likes to push to the limit of things. So a natural question is “how small can you make a wire” (or electrical device)? Based on my previous post, it’s hopefully obvious (now) that a molecule could provide mobile electrons and thus function as “molecular electronics.” (All you need is to use a molecule that allows electrons to freely move across its length.)

It has been relatively recent developments that allow us to actually measure single molecule electrical devices, and these measurements are still very difficult in general. At the same time, conventional silicon electronics (i.e., the memory and processors in your desktop and laptop computers) have been shrinking in size as well. Most people refer to “Moore’s Law,” which roughly suggests that we can double the number of electrical circuits (i.e., transistors) about every 2 years.

Since the size of computer chips themselves hasn’t changed significantly over the years, adding more circuitry into the same area on the chip requires smaller and smaller wires. Many current processors use 90nm wires and 65nm devices have been demonstrated. So there’s a technological driving force to research nanoscale electronics and molecular electronics in addition to the basic science aspect of measuring single molecules.