A new paper recently published in the journal ACS Nano introduces the wonder-material graphene to… potatoes and coconuts.
By applying the new technique, virtually any surface with a good amount of carbon atoms — including food, cloth, paper, cork, and even Kevlar — can be patterned into graphene.
In 2014, the research team led by Rice University chemist James Tour reported that shining a laser on a type of plastic called polyimide rearranges the carbon atoms into the familiar hexagonal structure of graphene.
The result was appropriately called “laser-induced graphene” (or LIG).
Later, the same was replicated in wood, although here it required a special chamber with a controlled atmosphere.
This time around, the tool of choice is a garden-variety carbon dioxide (CO2) laser commonly used for engraving, laser cutting, and surgery.
The key for success, the team reports, is “multiple lasing”, i.e., hitting the surface with a series of pulses at a certain power and wavelength.
While, in wood, a single pass is sufficient to achieve the desired result, many other materials require a little more convincing.
In such cases, the first pass makes a mess of the target atoms, producing a pattern called “amorphous carbon” (or black soot), while the second pass with a defocused beam nudges them right into graphene.
Furthermore, unlike during previous experiments with wood, the procedure was conducted in open air without the need for controlling the atmosphere.
As a demonstration, the researchers patterned a tiny, fully-functional electronic component on the surface of a coconut.
Given that LIG should theoretically be effective on any surface susceptible to charring, the limit to potential applications coincides with our ability to imagine them (edible electronics anyone?).
“(…) any carbon precursor that can be converted into amorphous carbon can be converted into graphene using this multiple lase method”, wrote the authors in their paper.
To get things rolling, the researchers had proposed the use of LIG to print biological sensors and RFID tags right into the surface of food to track its journey from farm to table.
In addition, LIG could also be used to rid drinking water of harmful pathogens.
The latter option is currently being explored by the company TerraForma, based on the finding that running electricity through LIG electrodes can both repel and kill unwanted bacteria.
Sources: abstract, acs.org, physicscentral.com.
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