Conducting polymer nanofibers enable electric currents in conformable devices

Organic electronic materials offer unique biomedical opportunities. A very promising approach is placing conductive fibers within a flexible and stretchable polymer substrate. Recently, a team of researchers in Canada have demonstrated that fibers produced by combining electrospinning with vapor phase polymerization (VPP) maintain high conductivity when stretched to 140 percent of their original length, as reported in Applied Physics Letters.

Professor of Chemical Engineering at Polytechnique Montreal Fabio Cicoira, who led the research, says that, notwithstanding their good knowledge of stretchable polymers and conducting fibers, creating such devices is challenging, in part because they are very sensitive to humidity. For this investigation, the researchers employed an electrospinning process whereby fibers of the polymer polyvinylpyrrolidone (PVP) containing the oxidant Fe(III) were ejected from a high voltage spinneret unto stetchable polydimethylsiloxane. Subsequently, the fibers were placed in a VPP reactor where they were exposed to monomer 3,4-ethylenedioxythiphene (EDOT) vapors. When in contact with the fibers containing the oxidant, EDOT polymerized to yield the conducting polymer poly-(3,4-ethylenedioxythiphene) doped with the counter ion tosylate.

Using an electron microscope and optical microscopy, the researchers determined that the embedded fibers were randomly oriented. The Cicoira team used a computer-controlled tensile tester to study the electrical properties of the fibers under stretching and found that the fibers continued to conduct effectively, albeit the conductivity diminished with strain. The fibers conducted 10-15 percent of the initial current at 140 percent strain (the polymer substrate breaks at 160 percent strain), which is biomedically significant as human skin can strain up to 30 percent.

Cicoira says this research demonstrates that electrospinning can enable fabrication of stretchable and conformable conducting devices. He hopes now to explore different fiber densities and diameters and also nonrandom fiber arrangements to see how these affect the conductivity.

Source: “Highly stretchable electrospun conducting polymer nanofibers,” by Fanny Boubée de Gramont, Shimming Zhang, Gaia Tomasello, Prajwal Kumar, Andranik Sarkissian, and Fabio Cicoira, Applied Physics Letters (2017). The article can be accessed at https://doi.org/10.1063/1.4997911 .