Flexible cold plasma jet with controllable length and temperature for hydrophilic modification

Abstract

With the advantages of high efficiency, simple equipment, good controllability, and the fact that they do no surface damage, atmospheric-pressure cold plasma jets are used to make solid surfaces hydrophilic. To transport the plasma jet effectively to the region to be modified and to reduce the amount of thermal damage to the surface during the modification, it is essential to control the transmission and temperature of the plasma jet from the distance. Flexible transmission and pre-cooling methods are proposed in this paper to solve this problem. An experimental device is constructed that mainly comprises the working gas, a power source, and a plasma generator. The test results show that (i) using a flexible catheter can extend the plasma transmission distance significantly and (ii) adjusting the driving voltage and gas flow allows the cold flexible plasma jet (FPJ) to reach several meters. Specially shaped jets such as plasma jet brushes can be generated conveniently based on the FPJ principle, thereby expanding the application range of the plasma. Pre-cooling the working gas with a vortex tube can lead to an FPJ with a simple structure without additional energy input and with a controllable temperature as low as −7 °C. The developed FPJ with a controllable length and temperature can be used to quickly modify various common solid surfaces, convert superhydrophobic surfaces into superhydrophilic surfaces, and preserve the microstructure of workpiece surfaces during modification.