Thanks to their portability and the non‐equilibrium character of the discharges, microplasmas are finding application in many scientific disciplines. Although microplasma research has traditionally been application driven, microplasmas represent a new realm in plasma physics that still is not fully understood. This paper reviews existing microplasma sources and discusses charged particle kinetics in various microdischarges. The non‐equilibrium character highlighted in this manuscript raises concerns about the accuracy of fluid models and should trigger further kinetic studies of high‐pressure microdischarges. Finally, an outlook is presented on the biomedical application of microplasmas.

Atmospheric radio‐frequency (rf) plasmas have attracted an increasing amount of attention due to its unparalleled capability for production of chemically reactive oxygen species (ROS). In this paper, we explore a one‐dimensional fluid model, incorporating 17 species and 65 key reactions, to investigate the generation mechanism of ROS in atmospheric He/O2 rf discharges. From the computational data the atomic oxygen density is almost linearly dependent on the power density and its largest value was observed at the oxygen admixture of 0.6% while altering the oxygen admixture at a constant power density, and an optimal oxygen admixture level of 0.3% is also found to produce the largest density of single delta oxygen (SDO) at a given power density.The dominant production and destruction reactions of ROS are also discussed based on the simulation results.

Several experimental and computational studies have shown that increasing frequency can effectively enhance the discharge stability in atmospheric radio-frequency (rf) discharges, but the frequency effects on the reactivity of rf discharges, represented by the densities of reactive oxygen species (ROS), are still far from fully understood. In this paper, a one-dimensional fluid model with 17 species and 65 reactions taken into account is used to explore the influences of the driving frequency on the production and destruction of ROS in atmospheric rf helium-oxygen discharges. From the computational results, with an increase in the frequency the densities of ROS decrease always at a constant power density, however, in the relatively higher frequency discharges the densities of ROS can be effectively improved by increasing the input power density with an expanded oxygen admixture range, while the discharges operate in the α mode, and the numerical data also show the optimal oxygen admixture for ground state atomic oxygen, at which the peak atomic oxygen density can be obtained, increases with the driving frequency.

Cover: The pie charts of the left side of this figure give the percentages of the main productive reactions for the atomic oxygen and SDO respectively; the right side show the simulated and inferred atomic oxygen density and SDO density versus the oxygen admixture, and the optimal oxygen admixtures of 0.6% and 0.3% can be observed in accordance with the simulation results, at which the peak atomic oxygen density and SDO density could be achieved, respectively. Further details can be found in the article by Y. T. Zhang .

In this paper a modelling study is performed to investigate the frequency scaling laws in atmospheric radio frequency discharges. By introducing the relaxation frequency of discharge plasmas, which links the electron density and excitation frequency, the relationships between excitation frequency and other discharge parameters, such as electron density, current density and sheath thickness, are revealed based on the analytical equations deduced from the model and then confirmed by the computational data. These scalings are effective to give insights into some discharge parameters which are not easily accessible in experiments such as electron density.