Low-Cost and Flexible Atmospheric Pressure Microplasma Devices and Applications on Maskless Surface Patterning
Date Issued
2015
Date
2015
Author(s)
Yang, Yao-Jhen
Abstract
A lot of efforts have been made on atmospheric microplasma systems since such type of plasma systems does not need vacuum systems, and has unique properties such as high electron density, high power density, and being able to create highly reactive environment in a local area. In this thesis, three types of cost-effective and flexible microplasma systems are reported: direct-current-driven paper-based coplanar microplasma device, paper-based dielectric-barrier-discharge-type microplasma array device, and printed-circuit-boared-based microplasma generation device. This work presents the first microplasma system fabricated on paper substrates. The direct-current-driven paper-based coplanar microplasma device is made by coating conductive carbon paste on paper substrates with screen printing method. Such type of devices has two types of discharge behaviors, namely, self-pulsing mode and stable mode, and the system can easily move into stable mode at high applied voltages. The mechanism of the two different discharge behaviors can be understood by looking into the load line of the system and the non-linear IV behavior of plasmas. By adding a drop of salt solution into the gap between the electrodes and acquiring the emission emanating from the plasma, we can detect the metallic elements with the optical emission spectra. The experimental results show that the detecting limit can be as low as nanogram. Because of the limitation of dc-driven plasmas, the plasma can only be ignited in a small area which limits the application of plasmas. We therefore design a paper-based dielectric-barrier-discharge-type microplasma array device. The device can operate in different atmospheres such as Ar, He, and air, and have discharges in every microcavity. Due to the fact that paper is a flexible substrate, the proposed device is able to generate plasmas even when the substrate is not flat. By utilizing the capillary force of paper substrates, we stored the liquid precursor in the fibers of paper, and create polyethylene-oxide-like patterns with the protein-repelling property on a glass substrate. The third type of microplasma generation devices is made of double-sided printed circuit board. The patterns on the copper electrode are fabricated by “toner-transfer method” without the need of clean room facilities. By taking the advantage of the flexibility of the device, we can create hydrophobic/hydrophilic contrast on flat and non-flat surfaces by depositing fluorocaronbon polymers or removing hydrophobic films. The device is able to pattern two surfaces simultaneously with patterned double-side printed circuit board on two sides. This technique was applied to fabricate surface-tension-confined mirofluidic devices. The microplasma devices proposed in this thesis are flexible in two ways: first, the substrates used here are flexible, and therefore the devices can be operated under non-flat conditions. Secondly, the electrode-patterning process does not need clean room facilities, and the users can design their own patterns anytime. The device fabrication process takes less than 30 min.
Subjects
microplasma
paper-based device
flexible
maskless
surface patterning
Type
thesis
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