According to foreign media reports, scientists have long known that eumelanin, a pigment that imparts color to the skin, hair and eyes of the human body, can conduct electricity. However, the natural form of eumelan does not have enough conductivity to be utilized, and no one knows how to mention its conductivity.
A recent study has changed this situation. In a paper published in the journal Frontiers in Chemistry, an interdisciplinary research team in Italy described a breakthrough process that can significantly improve the melanin conductivity.
Alessandro Pezzella, an organic chemist at the University of Naples, Frederick II, said: “This is a stepping stone, and a long process will start.”
Humans and other organisms do not respond to eumelanin, which means it can be used to coat medical implants or other devices that may enter the body. However, the natural form of eumelanin is too regular at the molecular level and the conductivity is not high. In previous studies, the conductivity of eumelanin could not be improved without the addition of metals or other chemicals, but these substances were considered foreign by the body. To improve the electrical conductivity of eumelanin without the addition of external factors, Pezzera and his colleagues developed a process of organizing molecules that allowed charge to flow from one electron to another.
Co-author, Paolo Tassini, an electrical engineer at the Italian National Institute for New Technologies, Energy and Sustainable Economic Development, said the process was “basically heated in a vacuum.” “In this way, you can completely remove oxygen and water vapor.” Without the extra molecules, melanin can conduct electricity better.
Tassini said that this process turned eumelanin into a “true conductor” with an increase in conductivity of more than nine orders of magnitude. The researchers called their results “High Vacuum Annealed Eumelanin” (HVAE).
However, melanin is still a pigment. Pezzela said that metals have a completely different range of conductivity, and HAVE is much less conductive. However, this is the first time that melanin can be used in the field of bioelectronics.
Phillip Messersmith, a materials scientist at the University of California, Berkeley, said: “I think this work is very important.” He did not participate in the study. However, he also pointed out that researchers still have to face many unresolved problems and challenges. A big problem is that when exposed to water, the melanin loses its conductivity and the conductivity of HAVE is greatly diminished. This will challenge the application of eumelanin in the human body, because the body is mostly composed of water. Future research may make melanin more adaptive. “I don’t think this is an insurmountable challenge,” said Messer Smith.
Pezzera said that their next step is to create a “very simple architecture” made by HAVE, “like a film.” In the future, this film will probably be applied to electronic devices used in the human body, but this still has a long way to go.
When researchers tried to heat eumelanin in a vacuum, they didn’t know what would happen. The high temperature of around 540 degrees Celsius does not simply burn these pigments. Instead, it makes the density of eumelane higher, just as an aluminum foil ball is squeezed more and more tightly. “We are very happy with what we found,” Tassini said.