Inactivation of S. mutans Using an Atmospheric Plasma Driven by a Palm-Size-Integrated Microwave Power Module

A low-power palm-size microwave power module for portable microwave-excited plasma applicable to biomedicine is integrated on a single printed circuit board for the first time. The designed board includes a power amplifier chip, a phase-locked loop (PLL) chip, and an impedance matching network with microstrip lines. In addition, as a part of the true one-chip integration of the plasma power module, the PLL is designed and fabricated in a semiconductor chip with a 0.18-μm CMOS technology for dedicated use to our plasma source. For the plasma generator, a 900-MHz coaxial transmission line resonator is used with argon gas flow. The designed plasma source is applied to the inactivation of S. mutans, showing three-log reduction within 180-s treatment. Measurements for the different initial concentrations (from 10⁵ to 10 ⁹ CFU/mL) are also conducted, and the outcomes are discussed. The results verify the feasibility of the proposed integrated microplasma source for use in dental treatments.