In-Vitro Analysis of Thin-Film Microplasma Discharge Devices for Surface Sterilization

Flexible microplasma discharge devices (MDDs) were successfully developed for inactivation of gram-negative bacteria such as
Escherichia coli
(
E. coli
) and
Pseudomonas aeruginosa
(
P. aeruginosa
), using ambient air as the sterilizing agent. The design of the electrodes influences the voltage distribution across the device and is an important contributor to the overall sterilization efficacy. Therefore, the voltage distribution across the top electrode of two different MDDs (designed in comb and honeycomb patterns) was analyzed initially using COMSOL Multiphysics simulation software. The honeycomb-patterned MDD resulted in a uniform distribution of the applied voltage as compared to the comb-structured MDD. The fabrication of MDD was realized using a flexible copper tape and polyethylene terephthalate (PET) film. Top electrodes of comb and honeycomb design were patterned using a laser ablation process. Similarly, rectangular and circular-shaped bottom electrodes were laser ablated for the comb and honeycomb-structured MDDs, respectively. PET was used as the dielectric layer, sandwiched between top and bottom layers of a flexible copper tape. The efficacy of the MDDs was analyzed by varying parameters, such as the gap distance between the MDD surface and bacteria (1–9 mm), treatment time (10–300 s), input dc voltage (4–8 V), and bacterial concentrations. Surface temperatures ranging from
${\sim }26~{^\circ }\text{C}$
to
${\sim }33~{^\circ }\text{C}$
were observed as the input voltage was increased from 4 to 8 V, respectively, for both MDDs. It was observed that the honeycomb-patterned MDD inactivated
${\sim }4$
Log
₁₀
of
E. coli
and
P. aeruginosa
cells in less than 20 s as compared to two minutes for the comb-structured MDD for an input voltage of 10 V. Bacterial viability against varying parameters using comb and honeycomb-patterned MDDs was analyzed and is presented in this article.