Investigation of dielectrophoresis and its applications in micro/nano fluidics, electronics and fabrications
Creators: name: Zhang, Chen
Publisher: name: RMIT University
Year: 2024

description: In this thesis, the author investigated the phenomenon of dielectrophoresis and its applications in electronics, microfluidics and optofluidics. Different configurations of microelectrodes, which were employed for such applications, were designed and fabricated. Their functionalities in producing dielectrophoretic (DEP) forces were evaluated through the simulation of electric fields. <br><br>It is believed that dielectrophoresis is one of the best approaches for depositing nanomaterials for device applications, since dielectrophoretically assembled materials are highly aligned and concentrated in desired locations; such characteristics ensure intimate contacts between interfaces and hence guarantee exceptional device reliability and functionality. To develop nanostructured electronic devices using dielectrophoresis, finger-paired electrodes were first employed to reveal the ability of AC electric fields in aligning and assembling nanomaterials. After that, micro-tip electrode arrays were utilized to develop electronic devices such as conductometric sensors and field effect transistors using dielectrophoretically deposited nanomaterials.<br><br>To realize the ability of DEP forces for manipulating particles in stationary liquid, a DEP-microfluidic device with micro-tip electrodes was utilized to comprehensively investigate the DEP behaviors of polystyrene microparticles using different AC electric fields. In a further study, the separation of carbon nanotubes (CNTs) from polystyrene particles was demonstrated using the same system. In order to achieve the most efficient DEP manipulation within liquid flows, curved electrodes were developed. With devices that use such a design, the author successfully conducted the following tasks in flowing liquid: the separation of polystyrene microparticles from CNTs, controllable focusing of polystyrene microparticles, sorting of polystyrene particles according to their dimensions, sorting of live and dead cells, trapping of polystyrene particles using pre-patterned CNTs, and the development of optofluidic waveguide using dielectrophoretically controlled silica particles. <br><br>Within this PhD research, the author achieved the following outcomes:<br>1. The DEP separation of nanostructures from microstructures was demonstrated for the first time. <br>2. For the first time, curved electrodes were developed to manipulate particles in flowing liquid using dielectrophoresis<br>3. The DEP trapping of polystyrene microparticles using pre-patterned CNTs was demonstrated for the first time. <br>4. An optofluidics waveguide, which was achieved using dielectrophoretically controlled silica particles, was demonstrated for the first time. <br>5. Gas sensors, which are fabricated using dielectrophoretically assembled and aligned NCNTs and NCNTs/Pt:Ni nanoparticles, were developed for the first time. <br>6. Field effect transistors were developed using dielectrophoretically deposited hybrid organic-inorganic materials and demonstrated for the first time. <br>