The development of nanoporous materials has received considerable attention innanofluidic studies in recent years. Furthering earlier research, the present thesisoffers a systematic study of two nanoporous materials—nanoporous aluminamembranes and carbon nanotube membranes—with a view to establishing theirelectroosmotic and fluid-flow behaviour at the nanoscale. The nanoporous aluminamembranes were studied for their own electroosmotic and fluid-flow properties,and utilised as templates for the production of the carbon nanotube membranesalso investigated in this study. The advanced control provided by the fabricationprocesses of both materials allowed for systematic investigations into the effectsof pore diameter and surface chemistry on both electroosmotic and pressuredrivenflows.Nanoporous alumina membranes were developed with pore diameters of < 10 nm.The effect of nanostructure and surface chemistry on macro wetting propertieswas analysed in detail. Flow enhancements were observed in hydrophilic aluminananochannels with inner diameters of 40 to 25 nm. Atomic force microscopyforce measurements provided further insight into fluid-solid interactions at thenanoscale. A systematic investigation of nanoporous alumina DC electroosmoticpumps with pore diameters down to 8 nm was also undertaken with sodiumtetraborate buffer operated at V = 10 V. Concentration polarization wasidentified as the principal challenge to sustained electroosmotic flow. Byoptimising the electroosmotic process, particularly the rig design and bufferconcentration, an EO pump was developed with a lifetime of up to 4 hours.Carbon nanotube membranes with a range of pore diameters were alsoinvestigated for their electroosmotic and pressure-driven flow properties. Thesynthesis of carbon nanotubes was optimised to obtain unblocked and functioningmembranes. Flow enhancements were observed in engineered carbon nanotubemembranes with pore diameters down to 16 nm. Electroosmotic flow rates incarbon nanotube membranes were similar to those of nanoporous alumina. Twoelectrolytes—sodium tetraborate and sodium chloride—were investigated inelectroosmotic flow experiments with carbon nanotube membranes. This allowedfor further investigation of electroosmosis and electric double layer overlap.
|Date of Award||31 May 2013|
|Supervisor||Davide Mattia (Supervisor) & Tom Arnot (Supervisor)|
- carbon nanotubes
- nanoporous alumina membranes