Graphene owl on food

Graphene cartoons created in food using laser technique

Image credit: Jeff Fitlow/Rice University

Researchers at Rice University have refined a technique for creating patterns of graphene on toast, cloth and other materials, paving the way for a new class of wearable and edible electronics.

Professor James Tour’s lab is responsible for developing laser-induced graphene (LIG); graphene etched onto surfaces as the material itself is converted into graphene – an atom-thick layer of carbon atoms in a hexagonal lattice – with the use of a laser. In the past, these researchers have drawn graphene patterns onto Girl Scout cookies and a range of other materials.

This is achieved by passing a laser with a defocused beam many times over the material, resulting in an LIG pattern appearing on its surface. In some cases, this creates a two-step reaction, in which the laser converts the surface into amorphous carbon, which then absorbs infrared light, turning into more orderly graphene.

This process can be carried out in the air at room temperature.

Previously, the researchers found that turning up the laser’s power did not produce a better result. Defocusing the laser and passing it over each spot multiple times allowed for better control over the process.

Materials that the team have successfully marked out with graphene include toast, cloth, paper, potatoes, coconut shells and cork. According to Tour, the common element of these materials is lignin, an organic polymer which contributes to the rigidity of cell walls. Materials with higher lignin content, such as coconut and potato, were easier to convert into graphene.

Among other potential applications, LIG could be used as a supercapacitor – a high-capacity capacitor – an electro catalyst for fuel cells, radio antennae and biological sensors. The addition of graphene patterns on various surfaces could be adopted to rapidly add conductive ID tags or sensors to products.

Tour added that LIG could be used to detect undesirable microorganisms on your food, such as E. coli, and warn the consumer when it is no longer safe to eat, and could also be used in flexible, wearable electronics.

“Very often, we don’t see the advantage of something until we make it available,” said Tour. “Perhaps all food will have a tiny [radio-frequency identification] tag that gives you information about where it’s been, how long it’s been stored, its country and city of origin and the path it took to get to your table.

“This has applications to put conductive traces on clothing, whether you want to heat the clothing or add a sensor or conductive pattern,” added Tour.

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