NSF Award
2435631
Electrically charged objects move when exposed to an electric field: this phenomenon is termed electrophoresis. Most research in this field has focused on electrophoretic motion in small-amplitude electric fields, where the velocity of the object is linearly proportional to the magnitude of the electric field. In contrast, this project will quantify the nonlinear electrophoretic motion of microscopic-sized charged particles immersed in an electrolyte solution under a large-amplitude field. A novel technique called Non-Antiperiodic Nonlinear Electrophoresis (NANEP) is proposed to enable net electrophoretic motion of such particles under an alternating (ac) field. Experimental measurements and computational modeling will be employed to provide proof-of-concept for NANEP. The ability to affect net electrophoretic particle movement through NANEP could lead to new methods for hierarchical assembly of particles. Further, it is envisioned that NANEP will provide the scientific foundation for new separation schemes for biomolecules in lab-on-a-chip microfluidic devices. The project will also have broader educational impacts including course development, undergraduate research experiences, and outreach activities.<br/><br/>The project will quantify the Non-Antiperiodic Nonlinear Electrophoresis (NANEP) of micro-scale colloidal particles via experiments and computations. The first objective is to predict NANEP via numerical solution of the nonlinear electrokinetic equations governing fluid flow, ion transport, and electrostatic fields in electrophoresis. The numerical scheme will employ a custom spectral element code with adaptive time stepping, which will enable efficient, accurate computation of NANEP across a wide range of the experimentally relevant parameter space. The aim is to determine which regions of this space result in the maximum net particle movement under NANEP. The second objective is to experimentally measure electrophoretic particle migration during NANEP. This will be accomplished by observing particle motion in a microfluidic channel under a non-antiperiodic field. Importantly, the results from these two objectives can be directly compared in an essentially parameter-free manner. The proposed research will provide the first computational predictions and experimental measurements for NANEP of colloidal particles.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
