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Human hair adapted into flexible displays for smart devices

11 Jun 2020

Queensland researchers team up with barbershop to turn trimmings into carbon nanodots for displays.

Researchers from Queensland University of Technology (QUT) and Griffith University, Brisbane, Australia, have developed a method for turning small hair strands into carbon nanodots, ultimately for displays. To produce the carbon nanodots, the team has developed a two-step process that involves breaking down the hairs and then burning them at 240ºC.

Associate Professor Prashant Sonar, Professor Ken (Kostya) Ostrikov and the research team, including PhD student Amandeep Singh Pannu, and in collaboration with Professor Qin Li of Griffith University, developed the new method of converting hair trimmings, which they sourced from the Ben Scissorhands barbershop at Kelvin Grove, Brisbane, with support from barber Benjamin Mir.

Professors Sonar and Ostrikov, who are chief investigators with the QUT Centre for Materials Science, said the research published in the journal Advanced Materials was “the first example of human hair waste being turned into highly luminescent carbon nanomaterial from which flexible light-emitting devices were fabricated.”

The processed nanodots were uniformly dispersed in a polymer and then allowed to self-assemble to form “nano-islands”, or small groupings of the nanodots. The formation of islands preserves the emission from a material in the solid state, which is essentially needed for incorporating any nanomaterial into a device. The nano-islands were thenused as an active layer in organic light-emitting diode (OLED) devices. The device lights up with a blue color when a modest voltage, approximately equal to two or three pencil batteries, was applied to the device.

“Hair waste is a big problem,” said Professor Sonar. “Human hair-derived carbon dot-based organic light-emitting devices could be used for certain indoor applications such as smart packaging. They could also be used where a small light source is required such as in signs or in smart bands and could be used in medical devices because of the non-toxicity of the material.”

‘Smart milk bottle’

PhD student Singh said from the start of his doctoral research he had been very keen to use waste and turn it into a valuable material. There could be many uses for small and cheap flexible OLED displays on Internet of Things devices, for example. He proposes one hypothetical example – a “smart” milk bottle, with an inbuilt sensor to give a real-time update of the milk’s expiry, with the information displayed on a screen on the bottle’s exterior.

Professor Sonar said the reason the researchers chose human hair as the source of the carbon dots was that hair is a natural source of carbon and nitrogen, which are key elements to obtain light-emitting particles. Another factor was that finding a practical use for waste hair could keep it from ending up in landfill.

Human hair is made up of proteins including keratin, which breaks down upon controlled heating. The material remaining after heating has both carbon and nitrogen embedded in its molecular structure, which gives it favourable electronic properties.

Professor Sonar said the carbon nanodots produced from human hair did not glow bright enough to be able to be used in television screens but could be used in a range of flexible screens from wearable devices to smart packaging.

“We have proven it works for human hair. We’re now interested if we could get the same results from animal hair,” Professor Sonar said. “Perhaps we could produce flexible OLEDs using small strands of wool from sheep or leftover dog hair from pet grooming salons.”

Amandeep will continue his research work on this direction under Professor Ostrikov and Associate Professor Prashant Sonar to explore more opportunities about using these carbon nanostructures for future electronics and underlying nanoscience.

Water testing potential

Professor Sonar, Professor Ostrikov, and the team of researchers, including Mr Singh, and in collaboration with Professor Li of Griffith University, have also published further research in Sustainable Materials and Technologies on how carbon dots made from human hair could also be used to develop a sensor that can perform real-time monitoring of chloroform levels in water treatment systems.

Chloroform is one of the by-products when chlorine is used for water disinfection. The World Health Organization (WHO) has set a safe limit of chloroform of less than 300 parts per billion in drinking water. Professor Sonar said the research had found the carbon dots made from human hair responded to the presence of chloroform with high sensitivity and selectivity.

“The creation of valuable material from human hair waste that has potential uses in both display and sensing opens up an opportunity towards a circular economy and sustainable material technology,” he said.

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