Engineers at Duke University have developed the world’s first fully recyclable printed electronics, eliminating the use of chemicals and replacing them with water in the manufacturing process. This could reduce the electronics industry’s environmental footprint and risks to human health.
Previously, researchers had already demonstrated the possibility of creating fully recyclable printed electronics using three carbon-based inks: semiconducting carbon nanotubes, conductive graphene and insulating nanocellulose. However, the biggest challenge was adapting the process to use only water instead of hazardous chemicals.
To achieve a water-based ink in which the carbon nanotubes were evenly distributed over a surface, the researchers added a detergent-like surfactant. However, the resulting ink did not create a dense enough layer of carbon nanotubes to allow a high current of electrons to pass through.
The problem was that the surfactant used to prevent agglomeration of the carbon nanotubes also prevented additional layers from adhering to the first layer. In a traditional process, these surfactants would be removed using high temperatures or harsh chemicals, leading to health and environmental risks.
To overcome this challenge, the research team developed a cyclic process in which the device is rinsed with water, dried with low-temperature heat and reprinted. In addition, the amount of surfactant used in the ink was reduced. With this approach, the researchers succeeded in creating fully functional, recyclable, water-based transistors.
The process also enabled the recovery and reuse of almost 100% of the carbon nanotubes and graphene used in printing, while nanocellulose obtained from wood can be recycled or biodegraded like paper. Although the process uses a significant amount of water, it is less than that required for the toxic chemicals used in traditional manufacturing methods.
Although there is still work to be done, the researchers believe that this method could be applied in the manufacture of other electronic components, such as screens and monitors, which are widely used in today’s society. By demonstrating the feasibility of a more environmentally friendly manufacturing process for electronic components, they hope to inspire the research community to continue working in this direction.
Although the performance of the developed thin-film transistors still falls short of today’s best standards, they are competitive enough to show that further progress towards more environmentally friendly electronic manufacturing processes is possible.