Tetsuji Shimizu1 Kazuya Kikunaga2 Hajime Sakakita1

1, Electronics and Photonics Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, , Japan
2, Advanced Manufacturing Research Institute, National Institute of Advanced Industrial Science and Technology, Tosu, , Japan

Biomedical applications using cold atmospheric plasmas (CAPs) have been studied extensively. At the beginning of this new field, sterilization and wound care were the main applications using CAPs because the plasma can supply reactive species similar to what the immune system produces. For sterilization, CAPs can inactivate bacteria including antibiotics-resistant strains, fungi, and viruses in tens of seconds to minutes. Within a few years, biomedical applications by CAPs expanded to include cancer therapy, gene transfection, activation of cell functions, blood coagulation, and regenerative medicine. From CAPs, there are several agents reacting with targets such as reactive oxygen and nitrogen species, charged particles, UV photons, heat, and electric field. So far, the biomedical effects driven by CAPs have been discussed mainly in terms of reactive species. However, the charged particles can also play an important role in the biomedical effects because they can also initiate chemical reactions. Moreover, the accumulation of charge on the target can influence the production of CAPs and the transport of reactive species. In addition, the developed electric field by the accumulated charge themselves can cause a biomedical effect. In order to understand the behavior of the charged particles, we aim to investigate a potential formation on an insulator film by the CAP treatment in this presentation.

The used CAP device was an atmospheric pressure plasma jet specially designed for blood coagulation. This device has a dielectric barrier discharge plasma source driven by an AC high voltage power supply with low energy consumption. The frequency of the applied voltage was ca. 62 kHz, and the peak-to-peak voltage was 3-6 kV with sinusoidal waveform. As the working gas, helium, argon or those admixtures was used in order to control the distribution of ion species. A plasma flare was ejected from a quartz tube of 1.4 mm in inner diameter and the insulator film was exposed to the plasma flare. The surface potential distribution on the insulator film was observed by using a static electricity scanner system which can measure an area of 30 x 30 mm2 at a spatial resolution of 1 mm within 3 s by scanning an object surface along a vibrating linear array sensor. This method allowed us to measure the potential distribution in a non-contact manner. For the plasma treatment, the insulator films were treated by the CAP for a certain period of time and the potential distribution was measured immediately after the plasma exposure. In the presentation, we discuss the potential profile developed by the CAP treatment and the charging mechanism by the charged particles from the CAP.