Polyimide‐Based Flexible Plasma Sheet and Surface Ionization Waves Propagation

Abstract

demands of treating complex 3D targets and irregular surfaces. Typical DBDs can hardly satisfy these requirements due to the narrow discharge gap and the rigid dielectric material. Thus it is of great significance to develop a specific plasma source which not only has the characteristics of high surface-compatibility and large-area coverage, but also maintains light, convenient and economical. The emergence of DBD plasma source using flexible material instead of the rigid one as the dielectric barrier provides a new way to solve this problem.Preliminary studies have been carried out focusing on manufacturing techniques and application effects of flexible plasma sources. Readle et al. [5] designed a flexible microcavity array plasma source which was fabricated from two bonded sections of Al mesh and used nanoporous alumina as an integral dielectric barrier, whose thickness was less than 100 µm, with microcavities reaching 50 µm in diameter. When bending the plasma source during the experiment, the characteristics of discharge current were almost unchanged, but the brightness of the curved array was only about 1/2 compared to the planar one. Another study reported by Cho et al., [6] in which the flexible plasma source used polyimide as dielectric barrier, showed that increasing the excitation voltage or reducing the thickness of the dielectric barrier would enhance the intensity of the discharge, leading plasma to diffuse from the edge of high-voltage electrode to the center gradually. There is also study reported in which the flexible plasma source was optimized to achieve a minimum displacement current and a maximum dissipated power. [7] In terms of application, flexible DBD plasma sources have shown remarkable effects in their use to microorganism inactivation, [8,9] wounds healing, [8,10] enhanced chemical deposition, [11] and hydrophilic or hydrophobic modification. [12] For example, after a 10-min treatment with the flexible plasma source, the microbial-load reductions of Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella Typhimurium were around 2 to 2.5 Log CFU g −1 in the samples respectively. [9] The flexible plasma source reported in reference [12] could be manufactured within 30 min and with a cost of less than 0.25 USD. The properties of being highly efficient and economical, together with unique surface-compatibility, make flexible plasma source a promising device for a more comprehensive application of non-thermal plasma. However, current Surface discharges on flexible substrates are attracting attention for their unique capability to generate large-scale non-thermal plasma and potential adaptability to complex objects in many fields, like biomedical inactivation and material processing. Two fundamental issues are manufacture of stable flexible plasma sources and mechanism of multiple surface ionization waves (SIWs) propagation on curved gas-solid interfaces. A polyimide-based flexible plasma sheet is realized through printed circuit board with a non-exposed electrode structure for disch...

Surface ionization waves propagating over non-planar substrates: wavy surfaces, cut-pores and droplets

“…Initiating plasma filaments intersected the apex of the hemispheres due to electric enhancement and polarization of the dielectric, followed by SIWs which propagated down the slopes of the hemispheres. Sun et al experimentally and computationally investigated SIWs propagating along a curved polyimide surface sustained with alternating powered and grounded electrodes buried in the dielectric [28]. They found that bending of the thin (100 μm) polymer sheet from being concave to the plasma to convex to the plasma increased electron densities by as much as 30%.…”

Synthesis and properties of modified thermoplastic polyimide films with good dielectric properties at high frequency and enhanced thermal stability via incorporation of rigid ester and biphenyl structural units

“…[11][12][13] That is to say, in order to achieve a faster signal transmission speed, the used dielectrics are required to possess the D k and D f values as low as possible. [14][15][16] Meanwhile, it is also known that the D k and D f values of the electrically insulating polymers are highly related with the water or moisture absorptions of the polymers because the absorbed water with high D k value ($ 80) usually increase the D k values of the polymers. 17 Thus, the polymer dielectrics with excellent combined properties, including high thermal and dimensional stability, low D k and D f values, and low water absorption are highly required for 5G and 6G high-frequency FCCL applications.…”

“…However, it has been well established that the delay time of the signal transmission is directly proportional to the signal transmission frequency, and it is also positively correlated with the D k and D f values of the dielectrics, such as the substrates, adhesives, and so on 11–13 . That is to say, in order to achieve a faster signal transmission speed, the used dielectrics are required to possess the D k and D f values as low as possible 14–16 . Meanwhile, it is also known that the D k and D f values of the electrically insulating polymers are highly related with the water or moisture absorptions of the polymers because the absorbed water with high D k value (~ 80) usually increase the D k values of the polymers 17 .…”

A 3D-printed fence-surface plasma source for skin treatment and its potential for personalized medical application

“…Coplanar DBD (CDBD) which utilizes the thin film as the dielectric could adapt to different surface shapes and treat a relatively large area. However, recent studies reported that the bending condition of CDBD could affect the discharge [28]. The wearable plasma source was proposed which could be used to treat the large area with irregular shapes [29][30][31].…”