A commercial air-fed and piezoelectric-driven plasma pen (piezobrush ^® , relyon plasma GmbH, Regensburg, Germany) including three different nozzles was investigated for its suitability as a medical plasma device. In this regard, potential risk factors for human health, which originate from gas temperature, thermal output, patient leakage current, ultraviolet radiation and gas emissions, were assessed according to DIN SPEC 91315:2016–06. As a result, safe treatment distances were determined for each nozzle. The antimicrobial efficacy was investigated subsequently by inhibition zone assays with five different clinical relevant microorganisms. All results were compared to an approved medical plasma source fed with argon (kINPen ^® MED, neoplas tools GmbH, Greifswald, Germany). It was observed that the antimicrobial efficacy differs not only between the two devices as a result from different feed gases, but also between the nozzles. This could be traced back to a different plasma chemistry, which accompanying Fourier-transform infrared absorption spectroscopy suggests. The measured physical properties of the piezoelectric plasma pen at the determined operating parameters do not show human health risks. Due to its distinct antimicrobial efficacy, the piezoelectric plasma pen shows a high potential for a medical application.

Based on a capacitively coupled plasma jet concept, an enhanced atmospheric pressure plasma jet setup for endoscopic applications is presented. Besides the favourable features of small dimension, flexibility and ability to operate in hollow bodies, new approaches for low patient leakage current, enhanced biological efficacy and reduced material erosion are subject of this work. It is found that a combination of neon feed gas, CO ₂ shielding gas and a current limited high voltage supply gives the best bactericidal results and, at the same time, reduces material erosion as well as patient leakage current.

In this work a cold atmospheric pressure plasma jet was mounted above a distilled water reservoir to study the influence of a water surface on reactive oxygen and nitrogen species (RONS) generation. The RONS, namely O ₃ and NO ₂ , were measured by multi-pass cell Fourier transform infrared absorption spectroscopy in the far-field of the jet. A shielding gas device was used to control the ambient environment of the effluent. The liquid surface has nearly no influence on the RONS dynamics as a function of shielding gas composition. It was found, however, that the interaction with the liquid surface increases the density of NO _x by a factor of 2–3 due to local increase in H ₂ O concentration through evaporation of water from the liquid surface. In contrast to the case of ambient humidity increase, this locally higher H ₂ O density distinctly influences the ratio of water to oxygen and nitrogen which results in a higher generation of OH molecules.

A novel flow-driven dielectric barrier discharge concept is presented, which uses a Venturi pump to transfer plasma-generated reactive oxygen and nitrogen species from a sub-atmospheric pressure ( 200 – 600 mbar ) discharge region to ambient pressure and can be operated with air. By adjusting the working pressure of the device, the plasma chemistry can be tuned continuously from an ozone ( O 3 )-dominated mode to a nitrogen oxides ( NO x )-only mode. The plasma source is characterized focusing on the mechanisms effecting this mode change. The composition of the device’s output gas was determined using Fourier-transform infrared spectroscopy. The results are correlated to measurements of discharge chamber pressure and temperature as well as of input power. It is found that the mode-change temperature can be controlled by the discharge chamber pressure. The source concept is capable of generating an NO x -dominated plasma chemistry at gas temperatures distinctly below 400 K . Through mixing of the processed gas stream with a second flow of pressurized air required for the operation of the Venturi pump, the resulting product gas stream remains close to room temperature. A reduced zero-dimensional reaction kinetics model with only seven reactions is capable of describing the observed pressure- and temperature-dependence of the O 3 to NO x mode-change.