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Title: Electroosmosis in nanoporous membranes : connecting material properties to flow behaviour
Author: Leese, Hannah
Awarding Body: University of Bath
Current Institution: University of Bath
Date of Award: 2013
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The development of nanoporous materials has received considerable attention in nanofluidic studies in recent years. Furthering earlier research, the present thesis offers a systematic study of two nanoporous materials-nanoporous alumina membranes and carbon nanotube membranes-with a view to establishing their electroosmotic and fluid-flow behaviour at the nanoscale. The nanoporous alumina membranes were studied for their own electroosmotic and fluid-flow properties, and utilised as templates for the production of the carbon nanotube membranes also investigated in this study. The advanced control provided by the fabrication processes of both materials allowed for systematic investigations into the effects of pore diameter and surface chemistry on both electroosmotic and pressure-driven flows. Nanoporous alumina membranes were developed with pore diameters of< 10 nm. The effect of nanostructure and surface chemistry on macro wetting properties was analysed in detail. Flow enhancements were observed in hydrophilic alumina nanochannels with inner diameters of 40 to 25 nrm. Atomic force microscopy force measurements provided further insight into fluid-solid interactions at the nanoscale. A systematic investigation of nanoporous alumina DC electroosmotic pumps with pore diameters down to 8 run was also undertaken with sodium tetraborate buffer operated at Δ V = 10 V. Concentration polarization was identified as the principal challenge to sustained electroosmotic flow. By optimising the electroosmotic process, particularly the rig design and buffer concentration, an EO pump was developed with a lifetime of up to 4 hours. Carbon nanotube membranes with a range of pore diameters were also investigated for their electroosmotic and pressure-driven flow properties. The synthesis of carbon nanotubes was optimised to obtain unblocked and functioning membranes. Flow enhancements were observed in engineered carbon nanotube membranes with pore diameters down to 16 run. Electroosmotic flow rates in carbon nanotube membranes were similar to those of nanoporous alumina. Two electrolytes-sodium tetraborate and sodium chloride-were investigated in electroosmotic flow experiments with carbon nanotube membranes. This allowed for further investigation of electroosmosis and electric double layer overlap.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available