Characterisation of an atmospheric-pressure plasma jet and plasma treatment of Escherichia coli resulting in growth inhibition

摘要

We present an atmospheric-pressure, non-thermal plasma jet consisting of relatively simple and cheap components. The plasma jet is ignited in a glass tube with helium gas flowing freely in to the surrounding air. The discharge behaviour of the jet is characterised by optical emission spectroscopy and time-resolved optical imaging. We observe the development of a characteristic "plasma bullet" during the discharge cycle. This sub-mm size plasma is created inside the discharge tube, and moves away from the tube at velocities up to 2×10~4 m/s. Further, the plasma jet is applied to the bacterium Escherichia coli and viability is assessed. The region in which the growth of the bacteria is inhibited is about 8 mm in diameter which is significantly larger than the 1 mm diameter of the (visible) plasma jet. This indicates that non-radiating plasma species like radicals and metastable atoms play an important role in the interaction with biological materials.