From AFM probe measurement of cell membrane strength to pinching force of run away electrons in streamers

Summary form only given. Dielectric Barrier Discharge (DBD) of atmospheric pressure plasma for biological sterilization is of great interests today, but there has yet to be a widely accepted explanation on which is the key mechanism responsible for the sterilization effect. A main candidate is oxygen excited states molecules that oxidize the bacteria, but these excited species are low in number and there are reports pure noble gas plasma also has sterilizat ion effect. Recently there has been a number of reports that use AFM probes to measure the mechanical strengths of various microorganisms and found their strengths range between 1–10 nN with cell membrane thickness ≪ 1 µm [1–3]. We performed a Monte-Carlo Particle-In-Cell simulation of streamer propagation in a Nitrogen discharge breakdown process in 300 Td, and documented the run away electron number, energy, and position in the streamer. We found that many run away electrons with energy as high as 20–30 eV exist. By assuming th ese run away electrons lose their momentum upon impinging the cell membrane, the force exerted on the cell membrane is around pN per electron. Thousands of run away electrons acting together are enough to penetrate the cell membrane and destroy the cell. Due to the high number of total electrons (≫ millions) available, we suggest that the impinging force of high energy run away electrons is a possible mechanism for biological sterilization.