The melanin in human skin could one day be used to create bionic implants, thanks to a special process harnessed by scientists in a landmark new study.
Dark brown melanin in skin has long been known to conduct electricity, but it has never been used in any application before.
This scientific breakthrough could help experts produce bionic implants that can replace missing or damaged parts of the body.
Melanin Pigments Transformed Via Annealing
Eumelanin is made up of millions of disorganized sheets that are layered on top of the other. Years ago, it was discovered that eumelanin has the capability to conduct electricity.
This discovery was celebrated because eumelanin is non-toxic, biodegradable, and does not elicit an immune reaction, said Alessandro Pezzella, one of the senior authors in the study.
Some studies have already tried to increase the conductivity of eumelanin by combining it with metals or superheating it into a graphene-like material. However, past attempts did not produce the biocompatible material they desired.
What Pezzella and his colleagues did in the new study was to put films of synthetic eumelanin through annealing by heating eumelanin sheets under high vacuum to straighten them up. It is similar to hair straightening under an iron, but here the researchers used pigment.
Paolo Tassini, Pezzella's coauthor, explained that the eumelanin films, which were no thicker than a bacterium, were heated under vacuum conditions from 30 minutes to six hours.
"We call the resulting material High Vacuum Annealed Eumelanin, HVAE," said Tassini.
Putting the eumelanin films under a vacuum worked and the films were slimmed down by more than a half. The eumelanin films also turned dark brown.
The research proves that reorganizing eumelanin molecules from random stacks into uniform, electron-sharing stacks was key to activating its potential.
The eumelanin conductivity increased to a value of more than 300 S/m after undergoing annealing at 600 degrees Celsius for at least two hours. In comparison, copper has a conductivity at around six times 107 S/m.
"Our process produced a billion-fold increase in the electrical conductivity of eumelanin," the researchers said.
Impacts Of The New Study
Since the conductivity of the films increased as the temperatures increased, scientists believe eumelanin can be tailored for a wide range of applications in bioelectronics and organic electronics.
In fact, researchers believe that the eumelanin films could be used to replace metals in tissue interfaces, such as brain implants used to treat Parkinson's disease or epilepsy, for bionic implants.
Although the results of the study are successful, however, there is one potential issue that could arise: when the eumelanin films are immersed in water, the condutcivity decreases.
Pezzella explained that further research must be done to understand the ionic and electronic features of eumelanin, which could be the key to understanding how eumelanin is used practically in implantable electronics.
The findings of the study are published in the journal Frontiers in Chemistry.