Hair today, flexible displays for smart devices tomorrow

Photo Credit: Bernadett/Adobe Stock

Researchers at Queensland University of Technology (QUT) in Brisbane, Australia have developed a process that mixes human hair waste in polymers to make flexible displays that could be used in future smart devices.

The process involves turning the small hair strands into carbon nanodots, which are tiny, uniform dots that are one-millionth of a millimeter.

To produce the carbon nanodots, the researchers developed a two-step process that involved breaking down the hairs – which were obtained from a local barbershop – and then burning them at 240 degrees C. According to QUT Associate Professor Prashant Sonar and Professor Ken (Kostya) Ostrikov, who are chief investigators with the QUT Centre for Materials Science, the research is 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. These nano-islands were used as an active layer in organic light-emitting diode (OLED) devices. The device lit up with a blue colour when a modest voltage, approximately equal to two or three pencil batteries, was applied to the device.

“Waste is a big problem,” Professor Sonar said.  “Human hair-derived carbon dot-based organic light-emitting devices could be used for some indoor applications such as smart packaging [and] also 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.”

Professor Sonar also said there could be many uses for small and cheap flexible OLED displays on Internet of Things (IoT) devices – one hypothetical example is a smart milk bottle, with a sensor built inside to give a real-time update of the milk’s expiry, with that information displayed on a screen on the outside.

The reason the researchers chose hair to extract carbon dots rather than something else, Professor Sonar said, was that hairs were 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 (polymers of amino acids) 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.

Source: Queensland University of Technology