Generation of Microplasma by Pulsed Discharge of a Liquid Filament

Summary form only given. We discuss a new scheme to create microplasmas by pulsed discharge in air with an ethanol filament that is created by electrostatic force between electrodes. We reported previously to use a droplet as the initial matter for the generation of microplasmas with liquid. These plasmas were operated by pulsed discharges, owing to the preparation of the liquid filament. The discharge was found to develop along the droplet surface. The discharge processes developing from the droplet to form microplasma are more complicated than those for gases. A small amount of ethanol, which remains on the anode surface after the discharge, experiences an attractive electrostatic force toward the cathode. As a result, the ethanol forms a micro-structure having conical shape that is known as Taylor cone. At the tip of it, an ethanol filament grows toward the cathode. These structures are affected by electrode separation, electrode configuration, and applied voltages. We propose to use the liquid filament as the initial matter for generating of microplasmas. The filament of ethanol aqueous solution with a diameter of approximately 10 mum and the length of 560 mum is formed between the electrodes with an electrode separation 1000 mum. The pulsed discharge also develops along the surface of liquid filament by applying a pulsed voltage. When electrolyte ethanol solution was used to form Taylor cone, corona discharge was observed at the tip of the cone. The corona appears only when the solution is operated as cathode. Although the deposited energy to corona discharges is small, the corona at the tip of the cone is advantageous to plasma processes because the atoms and molecules evaporating from the liquid surface flow into the discharge. Therefore, the corona discharge at the tip of the liquid is a candidate for highly functional micro plasma reactors.