These tiny cells could provide energy for pacemakers, hearing aids and limb prostheses
Researchers from the University of Georgia in the USA have developed a successful method for growing molecular hairs that conduct electricity - a first step in the development of biological fuel cells that can provide energy for pacemakers, hearing aids and organ prostheses. The scientific journal Chemical Science describes the new method as a "significant breakthrough in nanotechnology".
Chemist Jason Locklin from the University of Georgia and his research team succeeded in growing polymeric hairs consisting of chains of thiophane and benzene - aromatic compounds that are often used as organic solvents - attached to metallic surfaces to create extremely thin layers.
"The molecular strings are essentially highly compressed polymer chains that grew out of a metallic surface," said the lead researcher. "The structure of the layer is similar to a kind of toothbrush, where chains of conjugated polymers are like the bristles in the brush. We call these types of coatings polymer brushes. In order to make the chains densely packed in an extensive array, they must grow from the surface itself - a method we call the "assembly from within" approach."
In this approach, the scientists placed a monolayer of thiophane as the initial coating of the layer, and then "grew" additional thiophane or benzene layers on top of it using controlled polymerization methods.
"The beauty of organic semiconductors lies in the fact that their properties change depending on the size and number of their structural units," explains the researcher. The thiophane fragment itself is isolated, the researcher points out, "However, by joining together many thiophane fragments in a controlled manner, conductive properties for polymers are obtained."
And more importantly, says the researcher, "This method allows us to obtain controlled and cyclic structures of polymers, thus opening up the possibilities for diverse uses in electrical devices such as sensors, transistors and diodes." The thin layers are between five and fifty nanometers thick - too small to see, even under a powerful optical microscope.
The researcher explains that it is difficult to harness energy sources found in the living body, such as glucose, for use in biological fuel cells that could replace the need for batteries present in devices implanted in the body. And although humans have enzymes in the body that enable excellent conversion of chemical energy into electrical energy, "they are not efficient enough for this application because they have natural electrically insulating protective units that prevent good mobility of electrons from the active site to the electrode," he explains. "We hope that our molecular wires can provide a better means of mobility for the flow of electrons."
Although "flexible" electronics is an extensive field of research that is developing more and more, it is still in its infancy, the researcher points out. "For example, we still do not understand all the basic physics involved in the mobility of electric charge within organic materials."
The next step in their research is the development of appropriate applications. For example, their method of creating polymeric hairs could be used in a variety of devices that create an interface with living tissues, such as biochemical sensors, limb prostheses, implanted ears and effective hearing aids. "The layer itself could be used in transistors - or in photovoltaic devices such as solar cells," explains the researcher.
The research was published in the June issue of the scientific journal Chemical Communications.
