Coating of sealed microchannels and microcapillaries using atmospheric pressure microplasma

Surface modifications or coatings onto the inner walls of microchannels are vital in order to tailor the surface chemistry of the material for a number of biomedical and lab-on-chip applications. The technique of dry-process-based plasma polymerization is appropriate for modifying the surface chemistry of a material because it is a versatile method and is applicable for a wide variety of substrate materials. This thesis presents the preparation and characterization of the surface coating of sealed microchannels for biomedical and microfluidic applications. During the first phase of this study, a low cost and low power, high voltage plasma power supply was developed and tested by generating atmospheric pressure microplasma. A fast, sensitive and original overcurrent protection system was implemented to protect the power source in the case of short circuiting, and the microplasma reactor in the case of incidental arcing. In addition to this, the characterization of the atmospheric pressure microplasma was performed by measuring the spectroscopic and electrical parameters of the discharge. The parameters of the microplasma were also numerically computed. Predictions from the numerical simulations were found to be in close agreement with the experimental measurements. In the second part of this study, amino functional polymer films were deposited onto the inner surface of a glass microcapillary. The organic precursors allylamine, ethylenediamine, 3 aminopropyltriethoxysilane and hexamethyldisiloxane were used to perform the microplasma deposition. An original microplasma configuration which consisted of a perforated high voltage electrode and a ground electrode with large surface area was implemented to sustain a uniform glow discharge. Microplasma copolymerization was also carried out by mixing ethylenediamine with 3 aminopropyltriethoxysilane and hexamethyldisiloxane. The composition of monomers in the plasma co-deposition was precisely controlled using a new technique of liquid injection and helical mixing. The mixture of EDA and HMDSO has been copolymerized for the first time and the coatings obtained using this combination were found to be comparatively more stable. The resulting thin films were characterized using X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, atomic force microscopy, plasma emission spectroscopy, UV-visible spectroscopy, contact angle measurements and growth rate analysis. The third part of the thesis reports on a novel technique for coating in bonded polydimethylsiloxane (PDMS) and hybrid (glass/PDMS) microchannels using atmospheric pressure microplasma. The PDMS microchannels were fabricated using soft lithography technique. The hybrid microchannels were prepared using a low cost fabrication method without the requirement of a clean room. Also, an inexpensive setup for the bonding of microchips was developed using a dielectric barrier air plasma. In order to test the stability of the coating in the PDMS microchip, oil-in-water emulsions were formed in a T-shaped microchannel.EThOS - Electronic Theses Online ServiceGBUnited Kingdo