Laser Ablated Microplasma Discharge Device for Inactivating Bacteria Suspended in Liquid Media

A flexible microplasma discharge device (MDD) was successfully developed for inactivating multi-drug resistant Gram-negative (Escherichia coli, Pseudomonas aeruginosa) and Gram-positive (Staphylococcus aureus, Bacillus subtilis) bacteria, under ambient operating conditions. The MDD consists of a flexible polyethylene terephthalate (PET) film as the dielectric layer and copper tapes as electrodes. The copper tapes were patterned in a honeycomb and circular design using laser ablation to create top and bottom electrodes, respectively, and the PET was sandwiched between the electrodes to fabricate the MDD. The efficacy of the MDD to inactivate bacterial cells in phosphate buffer saline (PBS) was investigated by testing the effect of varying treatment times and input voltages, ranging from 1 to 10 minutes and 6 to 10 V, respectively. Around 8log10 reduction of all bacterial viability were achieved when the MDD was activated for less than 11 minutes at an input voltage of 10 V. The corresponding decimal reduction time was calculated, and it was observed that E. coli and P. aeruginosa were most resistant to radiation from microplasma with a D-value of around 5 and 1.9, respectively. The flexibility of the device was also tested by bending the MDD on surfaces with a radius of curvature of 25 mm and 50 mm. The calculated power density of the MDD in bent condition and flat state was same, clearly indicating that the MDD is flexible. The optical spectra of the microplasma radiation and surface temperature of the MDD were also characterized and are reported in this paper.