Technological watch

QUT researchers have turned human hair waste into flexible displays that could be used in future smart devices. Researchers have developed a method of turning the small hair strands into carbon nanodots, which are tiny, uniform dots that are one-millionth of a millimeter. The researchers sourced the hair scraps from the Ben Scissorhands barbershop at Kelvin Grove, with barber Benjamin Mir happy to support the research project.
A New Two-step Process
To produce the carbon nanodots, the researchers developed a two-step process that involved breaking down the hairs and then burning them at 240 degrees Celsius.
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 color when a modest voltage, approximately equal to two or three pencil batteries, was applied to the device.
“Waste is a big problem. Human hair derived carbon dot-based organic light-emitting devices could be used for some 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,” Professor Prashant Sonar said.
Smart Milk Bottle with Sensor
Researchers have been very keen to use waste and turn it into a valuable material. The small and cheap flexible OLED displays can be used for many applications for 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 researchers chose hair to extract carbon dots, rather than something else, 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.

The new carbon nanodots 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. Perhaps we could produce flexible OLEDs using small strands of wool from sheep or leftover dog hair from pet grooming salons,” Professor Sonar said.
Highly-sensitive Response to Chloroform Levels
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.
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,” professor Sonar said.