Instrumentation for a plasma needle applied to E. coli bacteria elimination

Microplasmas are nowadays a powerful tool with multiple practical applications. The performance of a specific instrumentation for a plasma needle capable of producing non-thermal plasmas and a DBD reactor able to produce atmospheric pressure plasmas, both of them designed and already constructed, is reported. These devices operate at 13.56 MHz and are driven by a specifically built radio frequency (RF) resonant converter. The reactors, which operate at atmospheric pressure in a He-air gas mixture at a 1.5 SLPM flow, have been successfully applied to eliminate E. coli bacteria. In the needle case, bacterial samples were submitted typically to a 500 V peak voltage plasma discharge for 120 s. In the DBD treatment, the samples were processed with typical 750 V peak voltage plasma discharges for 80 s. The sample pH was used as a criterion to measure the effectiveness of the plasma treatment, in such a way that the return to the basal pH value after the treatment can be assumed as the validation of the complete bacterial elimination.