(441a) Integrated AC Electrokinetic Microdevices

Manipulating the most basic lab-on-a-chip (LoC) ingredients - particles, cells and fluid ? in closed micro-channel geometries is a requirement of any LoC-type device. Specific tasks ? fluid pumping, sample mixing, bioparticle concentration, separation, and analyte detection ? require micro-sized pumps, mixers, concentrators, separators and sensors. Conventional solutions to this problem involve scaling down peristaltic, diaphragm, and other popular macro-scale mechanical pumps or micromanipulators towards micro-scale dimensions. However, most such devices contain moving parts which can lead to clogging and cell lyses, and render them unreliable and unsuitable for biological applications.

Due to such drawbacks, the use of electrokinetic (EK) devices with no moving parts to transport, mix fluid and manipulate cells and particles has attracted considerable attention. The term Electrokinetic is used to describe the motion of a liquid or particle under the influence of an external microelectrode-driven electric field. EK phenomenon can be quite powerful at the micro-scale; the well developed integrated circuit (IC) fabrication techniques from the microprocessor industry have made the fabrication and assembly of microelectrodes into microfluidic geometries a simple reality. This allows the experimentalist to deliver highly spatially controlled alternating current (AC) or direct current (DC) electric fields and integrate electrokinetics into microfluidic devices for specific diagnostic tasks.

The design, control, and implementation strategies, however, of EK devices for use in LoC applications, specifically in biological microfluidic applications, can be non-trivial and exceedingly challenging. Here we present the discovery, development and optimization of such strategies and their integration into a fully functional portable LoC device for sample control and manipulation. Specifically we discuss the integration of micro-electrode induced AC electrokinetic phenomena such as dielectrophoresis and AC electro-osmosis within microfluidic systems for use in biological and nanoscale lab-on-a-chip applications ranging from genetic detection to yeast cell and malaria infected blood cell characterization and sorting. It will be shown that such integrated electrokinetic effects satisfy the major requirements of next generation microfluidic diagnostics - namely fluid metering, sample concentration, and detection and quantification.