In vitro inactivation of bacteria by a flexible thin-layer cold plasma source under bending deformation

Low-temperature plasma is widely used in the field of biomedical treatment for its non-thermal and high-efficiency sterilization effects on bacteria, fungi, and viruses. However, it still remains a hot issue on how the plasma sources apply to complex three-dimensional objects during the treatment. Flexible substrate-based plasma sources are gaining popularity due to their exceptional ability to adapt to uneven surfaces and wide range of plasma coverage. Through a printed circuit board with a non-exposed coplanar electrode configuration for discharge, a polyimide-based flexible plasma sheet is created and its plasma generation characteristics are obtained by experiment. The inactivation efficacy on S. aureus and P. aeruginosa is investigated by varying treatment times ($30,60,90$ and 120 seconds). Activations of the plasma sheet for 30 s and 120 s reduce both S. aureus and P. aeruginosa on the flat surface by around 2.5 and 5 log colony forming units (CFU). However, the plasma antibacterial effect decreases when treating curved surface, while being regained after conforming the plasma sheet to the surface. Benefits to a better design and future use of flexible plasma sources will result from this work.