Evaluation of electric field and charge on bio-substrates induced by nanosecond pulsed helium plasma jet

Non-thermal atmospheric-pressure plasma jets are of interest to various biomedical applications including bacterial inactivation, surface modification and sterilization, wound healing and tumor apoptosis. The electric field and charge near the bio-substrates were considered important agents influencing the plasma-induced biomedical effects due to the possible electroporation and chemical processes. This work investigated the charges and electric field in the bio-substrates with the plasma jet impinging on the substrate. Ultrapure water, PBS (phosphate buffered saline) solution and pig skin were used as the substrates. The plasma jet was based on a dielectric barrier discharge (DBD) configuration, powered by 180 ns, 6 kV pulses at 1 kHz and with helium flow of 985 sccm (standard cubic centimeters per minute). The charges delivered to the substrates are evaluated by jet current and compared. There is an optimal gap distance of 5mm for water and 10mm for PBS solution and pig skin. Pig skin consumes the most energy. The electrical field is evaluated by measuring the potential difference in water, which shows that there exists electric field remaining after plasma jet strikes on the water surface. Applying higher voltage can get higher electric field in water.