Inactivation of B. subtilis Spores Using Flexible Microplasma Discharge Device

A flexible microplasma discharge device (MDD) was successfully fabricated for inactivating spore forming bacteria such as Bacillus subtilis. The device was operated under ambient conditions using ambient air as the inactivating agent. A flexible polyethylene terephthalate (PET) film was employed as the dielectric layer and sandwiched between layers of flexible copper tape. The top and bottom electrodes were laser ablated in a honeycomb and circular pattern, respectively. The efficacy of the MDD was analyzed by irradiating microplasma on to the surface of agar on a petri dish, that was inoculated with B. subtilis. One-and seven-days old culture of B. subtilis were used to investigate the effectiveness of MDD for varying treatment time. It was observed that the device was able to inactivate both one- and seven-days old culture of B subtilis from only one second of exposure time and achieved 4log10 reduction. The performance of the MDD towards vegetative and sporulated cells of B. subtilis are analyzed and presented in this paper.