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Low-power beam makes laser-induced graphene

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Scientists have made laser-induced graphene with a low-power laser mounted in a scanning electron microscope, an advance expected to lead to the wider commercial production of flexible electronics and sensors.

The process creates Laser-induced graphene (LIG) with features over 60 per cent smaller than the macro version of the material and almost 10 times smaller than typically achieved with an infrared laser.

The findings, developed in the labs of Rice University chemist James Tour and Tennessee/ORNL materials scientist Philip Rack, are detailed in ACS Applied Materials & Interfaces.

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"A key for electronics applications is to make smaller structures so that one could have a higher density, or more devices per unit area," Tour said in a statement. "This method allows us to make structures that are 10 times denser than we formerly made."

Scientists recorded the formation of laser-induced graphene made with a small laser mounted to a scanning electron microscope (Image: Tour Group)

To prove the concept, the lab made miniscule flexible humidity sensors directly fabricated on polyimide, a commercial polymer. The devices were able to sense human breath in 250 milliseconds.

"This is much faster than the sampling rate for most commercial humidity sensors and enables the monitoring of rapid local humidity changes that can be caused by breathing," said the paper's lead author, Rice postdoctoral researcher Michael Stanford.

The smaller lasers pump light at a wavelength of 405nm, in the blue-violet part of the spectrum. These are less powerful than the industrial lasers the Tour Group and others are using to burn graphene into plastic, paper, wood and even food.

Laser-induced graphene
A scanning electron microscope image shows two traces of laser-induced graphene on a polyimide film. A laser mounted to the microscope was used to burn the patterns into the film. The technique shows promise for the development of flexible electronics (Image: Tour Group)

The SEM-mounted laser burns the top five microns of the polymer, writing graphene features as small as 12 microns.

Tour said the new Laser-induced graphene process offers a new path toward writing electronic circuits into flexible substrates like clothing.

"The LIG process will allow graphene to be directly synthesised for precise electronics applications on surfaces," he said.