Shocking development shows how plastic electrical insulation breaks downShocking development shows how plastic electrical insulation breaks down

Xuanhe Zhao, an assistant professor of mechanical engineering and materials science at Duke's Pratt School of Engineering, said that researchers have known for some time that polymers eventually break down when subjected to an increasing electrical voltage, but they can now watch the process as it happens in real time.

The Duke researchers attached a soft polymer to another rigid polymer layer, which acted as a protective substrate, and enabled the observation of the deformation process without incurring the breakdown. The polymer-substrate was then subjected to various electrical voltages, with the effects observed under a microscope.

Zhao compared the process to bread dough rising in a bowl, so that the top surface of the dough may fold in upon itself and form creases due to compressive stresses developing in the dough. When the voltage in the testing reached a critical point, the compressive stress induced a pattern of creases on the polymer, and if the voltage increased further, the creases evolved into craters or divots, as the electrical stress pulls the creases open. Zhao noted that polymers typically break down electrically immediately after the creasing, which can cause failure in applications like insulating cables and organic capacitors.

The researchers said the substrate they developed for the experiments not only allowed for the creasing to be seen, but it could also be the start of a new approach to improving the ability of wires to carry electricity, as well as function in the emerging field of energy harvesting. Zhao was the senior scientist in the series of experiments performed by graduate student Qiming Wang and published online in the Physical Review Letters.