Elizabeth Melvin

PhD, Chemical Engineering, 2011
North Carolina State University

M.S., Chemical Engineering, 2008
North Carolina State University

B.S., Chemical Engineering, 2002
Ohio State University, Columbus, Ohio

Research Focus: Cell Sensing and Manipulation Using AC Electric Fields

We aim to improve and develop biosensing methods and devices using AC electric fields to manipulate and detect cells and particles in microfluidic devices. We are currently working on two major congruent projects in two regimes of AC electric field generation; the high voltage, low frequency regime and the low voltage, high frequency regime.

Impediometric Biosensing

At low voltages (10 – 100 mV) and high frequencies (> 100 kHz), impedance across interdigitated electrodes is used to detect the presence of a desired analyte or cell type. Impediometric biosensing is rapid and requires sample sizes less than 100 µL. Cells are brought to the surface of the electrodes by settling, agglutination, and manipulation of magnetic particles. Magnetic particles are also functionalized so as to specifically detect a particular cell type. Preliminary experiments have shown magnetic particles to provide the most sensitive detection.

Particle Collection

At high voltages (0.8 – 5 V) and low frequencies (< 10 kHz), AC electroosmosis (ACEO) and dielectrophoresis (DEP) can be used to manipulate particles and fluid flow to direct particle collection in a predetermined area in a microfluidic chamber. In collaboration with RTI International (Research Triangle Park, NC), a particle collection device was developed to induce ACEO flow above a quadrilateral array of asymmetric planar gold microelectrodes (below 5.0 kHz). The equally generated flows are directed towards the center of the chip, creating a central stagnant region. Above 2.5 kHz, particles and cells are collected in the small electrode gaps by DEP. As most biological detection requires high electrolyte solutions, the collection device can be altered and tuned to meet the needs of a variety of applications. Ultimately, it is intended to couple the particle collection technique with evanescent wave detection methods by etching an optical waveguide in the stagnant region of the chip.

Figure 1: Schematic of ACEO/DEP Particle collection device and microfluidic chamber.