Effects Of Materials On Electric Field In A Nanosecond Pulsed Helium Plasma Jet Impinging On Biomaterials*

Nonequilibrium nanosecond pulsed atmospheric pressure plasma jets (ns-APPJs) produce reactive plasma agents including reactive oxygen species (ROS), charged particles, electric field, and UV photons, which are known to play crucial roles in various applications such as sterilization, wound healing, cancer treatment, and materials processing. When an APPJ impinges on a biomaterial, the property of the biomaterial may influence the formation of the plasma and the associated chemistry, resulting in different ROS productions ^[1,2]. In addition, the distribution and temporal development of the electric field in the ns-APPJ may also be impacted.  In this study, we compared the electric field of a helium ns-APPJ, powered by 200 ns, 7 kV pulses at 1 kHz, impinging on ultrapure water, phosphate-buffered saline solution (PBS), and pigskin. Utilizing the electric field-induced second harmonic (E-FISH) method enabled by a femtosecond laser, a cylindrical lens for beam-shaping, and a gated intensified charge-coupled device (ICCD), the absolute electric field on the order of tens of kV/cm was observed. It was the strongest near the needle tip, with PBS inducing the highest electric field. The effects of biomaterial property on the electrode configuration, the ionization wave propagation, and hence the electric field in the plasma are discussed.