Atmospheric pressure plasma penetrating into multilayer fiber membrane

Atmospheric pressure cold plasma has been extensively used for low-melting fiber membrane surface modification to improve their inert properties. A significant challenge arises from the plasma's limited propagation within the microchannels in fiber membranes that results in ununiform treatment. Here, we studied the discharge dynamics during plasma penetration in multiplayer fiber membranes when treated by a helium atmospheric pressure plasma jet. The fiber membranes were delicately prepared by an electrostatic spinning direct-writing technology with controlled dimensions and micrometer spatial resolution. It was observed from the ns images that increasing the layers of fiber membrane would impede plasma penetration, which was further interpreted by 2D plasma fluid modeling that highlighted the effects of microchannels' tortuosity, radius, and porosity. On this basis, a theoretical model derived from electron avalanche theory was proposed to elucidate the dependence of electron multiplication on the tortuosity, radius, and porosity. It suggested that smaller tortuosity, larger radius, and higher porosity favor the plasma penetration in the multiplayer fiber membranes.