Date of Award


Document Type


Degree Name

Doctor of Philosophy in Chemical Engineering (PhD)

College, School or Department Name

Department of Chemical Engineering


Adrienne R. Minerick


Alternating current (AC) electric signal has been widely applied in microfluidic systems to induce AC electrokinetic behavior. AC electrokinetic phenomena including AC electrophoresis, AC dielectrophoresis, AC electroosmosis flow and AC electrothermal flow are widely applied in (bio)particle sorting, separation and concentration and micropumps. However, numbers of non-ideal AC electrokinetic behaviors have been reported: human erythrocyte deformation in AC dielectrophoresis system has been observed; flow reversal in AC electroosmosis flow pumps has also been reported. In this dissertation, a systematic study on human erythrocyte crenation in AC dielectrophoresis system was firstly conducted. Multiple possible physical mechanisms inducing cell crenation including temperature, temperature jump, pH, shear force and osmotic pressure was examined. pH change and osmotic pressure change induced by ionic concentration change was attributed as mechanisms induced cell crenation. Such pH change and ionic concentration gradient in AC non-uniform electric fields were then further studied. pH change was detected using Fluorescein sodium salt in sodium chloride solution at relative frequency ~5 to 25 times to electrode charging frequency. Time, spatial, frequency and peak-to-peak potential dependencies have been examined on such pH change and pH gradient. Ion concentration behavior was detected by using ionized FITC molecule as fluorescing ion dissolved in inert solvent methanol. Electrode surface is also coated with HfO2 dielectric layer to minimize effect from electrochemical reaction on FITC emission intensity. Time, spatial, frequency and peak-to-peak potential dependencies have also been examined on ion concentration change and ion concentration gradient. Both pH change and ion concentration change have been observed under high relative AC frequency.