  Inactivation of microorganisms on sensitive surfaces by cold atmospheric
plasma (CAP) is one major application in the field of plasma medicine because
it provides a simple and effective way to sterilize heat-sensitive materials.
Therefore, one has to know whether plasma treatment affects the treated
surfaces, and thus causes long-term surface modifications. In this
contribution, the effect of cold atmospheric Surface Micro-Discharge (SMD)
plasma on different materials and its sporicidal behavior was investigated.
Hence, different material samples (stainless steel, different polymers and
glass) were plasma-treated for 16 hours, simulating multiple plasma treatments
using an SMD plasma device. Afterwards, the material samples were analyzed
using surface analysis methods such as laser microscopy, contact angle
measurements and X-ray photoelectron spectroscopy (XPS). Furthermore, the
device was used to investigate the behavior of Bacillus atrophaeus endospores
inoculated on material samples at different treatment times. The interaction
results for plasma-treated endospores show, that a log reduction of the spore
count between 4.3 and 6.2 can be achieved within 15 min of plasma treatment.
Besides, the surface analysis revealed, that there were three different types
of reactions the probed materials showed to plasma treatment, ranging from no
changes to shifts of the materials' free surface energies and oxidation. As a
consequence, it should be taken into account that even though cold atmospheric
plasma treatment is a non-thermal method to inactivate microorganisms on
heatsensitive materials, it still affects surface properties of the treated
materials. Therefore, the focus of future work must be a further classification
of plasma-caused material modifications.

Plasma Physics