Plasma Applications

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Atmospheric Pressure Plasma ‐ From Diagnostics to Applications

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(2A):844-852

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2009;106(12):644-637

1-20

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**71**

**Chapter 4**

**Abstract**

**1. Introduction**

gap an electric field 104

specific for nonequilibrium plasmas [4].

Applications of Dielectric Barrier

*Kazuo Shimizu, Jaroslav Kristof and Marius Gabriel Blajan*

Dielectric barrier discharge microplasma is a nonthermal plasma discharge at atmospheric pressure which due to the micrometer size dielectric layer between the grounded and high-voltage energized electrodes enables to drive the device at less than 1 kV. Microplasma is an economical and ecological alternative for conventional technologies used for NOx removal, indoor air cleaning, surface treatment of polymers, biomedical applications such as transdermal drug delivery, or as an actuator. In this chapter, microplasma applications such as indoor air purification, skin treatment for drug delivery, particle removal, and flow control are presented.

**Keywords:** dielectric barrier discharge, microplasma, indoor air purification, plasma

Microplasma is a term used typically for referring to gas discharges that have dimensions ranging from few micrometers up to few millimeters. The breakdown voltage which is the voltage that is required to ignite a discharge depends on the product of pressure p and discharge gap d, that is also known as the Paschen curve. According to the Paschen curve, at atmospheric pressure, the breakdown voltage can be kept at low values if the discharge gap is below 1 mm. Thus the typical operating parameters of microplasmas (pressures up to and exceeding 1 atmosphere and discharge gaps below 1 mm) correspond to the values of p and d product similar to the values of the large-volume low-pressure plasmas but with much higher energy densities [1–3]. The microplasma presented in this chapter is a nonthermal plasma discharge at atmospheric pressure. It is a type of dielectric barrier discharge (DBD) generated using a configuration having a dielectric material covering the electrodes and a narrow discharge gap of micrometer size between electrodes. Because it is generated at relatively low discharge voltages of about 1 kV, the reactor has small dimensions and requires only small-sized power supplies. Considering the electrodes covered by a dielectric layer with a dielectric constant of εr = 104

according to the law that states the electric displacement field inside the capacitor formed by the two dielectric layers and the air gap is constant, it results in the air

assures the formation of nonthermal plasma at a discharge voltage about 1 kV. The temperature estimation of the microplasma discharge using emission spectroscopy shows high electron and low rotational temperatures. These temperatures are

a discharge gap of 10 μm, it has obtained a high electric field E = 107

times higher than the electric field in the dielectric layers. At

and

V/m that

–108

drug delivery, particle removal, electrohydrodynamic flow, plasma actuator

Discharge Microplasma

#### **Chapter 4**
