June 22, 2009: Researchers from the U. of Georgia have developed a method to grow molecular polymer chains into miniature fuel cells that can conduct electrical charges, with potential use in devices including pacemakers, cochlear implants, and prosthetic limbs.

The polymer chains are grown as an ultrathin (5-50nm) film from the surface in a “grafting” approach, in which a single layer of thiophene is laid down as an initial coating, followed by built-up chains of more thiophene or benzene using a controlled polymerization technique. The structure is said to resemble toothbrush bristles. Thiophene is an insulator, “but by linking many thiophene molecules together in a controlled fashion, the polymers have conducting properties,” notes Jason Locklin, UGA chemist and lead of the paper which appeared in the June issue of the journal Chemical Communications.

The technique enables systematic control to vary the polymer architecture, which opens up application in devices such as sensors, transistors, and diodes. Fuel sources within the body are difficult to harness, he pointed out, and those that are good at chemical-electrical energy conversion (e.g. enzymes) don’t transmit the electricity well due to insulating layers. “Hopefully our molecular wires will provide a better conduit for charges to flow.”

Next step in the research is to pinpoint specific applications — e.g., interfacing the polymer brush directly with living tissue as a biochemical sensor, prosthetic limb, pacemaker, or bionic ears. Other possible applications include transistors (think organic semiconductors) or photovoltaic devices.

The work was funded by the Petroleum Research Foundation.

AFM image of a 42nm PPh film prepared via SI-KCTP. (Source: Chemical Communications)