Humble coal to pave the way for future electronics

New York: Using the low-tech material coal, engineers from the Massachusetts Institute of Technology (MIT) have built a simple electrical heating device that can be used for defrosting car windows or airplane wings or as part of a biomedical implant.

They have also for the first time characterised in detail the chemical, electrical and optical properties of thin films of four different kinds of coal - anthracite, lignite, and two bituminous types.

“When you look at coal as a material and not just as something to burn, the chemistry is extremely rich," said lead researcher Jeffrey Grossman from the Department of Materials Science and Engineering (DMSE) at MIT.

The question he wanted to ask is: "Could we leverage the wealth of chemistry in things like coal to make devices that have useful functionality?"

The answer, he says, is a resounding yes.

Part of the challenge was to figure out how to process coal.

The researchers developed a series of steps to crush the material to a powder put it in solution then deposit it in thin uniform films on a substrate -- a necessary step in fabricating many electronic devices - from transistors to photovoltaics.

Even though coal has been one of the most widely used substances by human beings for centuries, its bulk electronic and optical properties had never really been studied for the purpose of advanced devices.

The simple heating device the team made provides an end-to-end demonstration of how to use the material - from grinding the coal to depositing it as a thin film and making it into a functional electronic device.

The doors are now opened for a wide variety of potential applications through further research.

The big potential advantage of the new material, Grossman says, is its low cost stemming from the inherently cheap base material, combined with simple solution processing that enables low fabrication costs.

The findings were reported in the journal Nano Letters.