Particle Dynamics in a Dielectrophoretic Microdevice

Abstract

A dielectrophoretic device has been designed to trap, separate, and concentrate biological components carried in solution. The operating principle of the device is the dielectrophoretic interaction between the spheres and the fluid. The device was designed and manufactured by at Purdue University [6]. The device consists of a microchannel with a depth of 11.6 μm, width of 350 μm, and length of 3.3 mm. The channel was anisotropically etched in silicon to produce a trapezoidal cross-section. The channel was covered by a piece of anodically bonded glass. A schematic view and digital photo of the device are shown in Figure 13.1. Bright regions represent platinum electrodes and the dark regions represent the electrode gaps. The electrodes are covered by a 0.3 μm thick layer of PECVD silicon dioxide, which insulates the electrodes from the liquid medium, suppressing electrolysis. The electrodes are arranged in interdigitated pairs so that the first and third electrodes from Figure 13.1 are always at the same potential. The second and fourth electrodes are also at the same potential, but can be at a different potential than the first and third electrodes. An alternating electric potential is applied to the interdigitated electrodes to create an electromagnetic field with steep spatial gradients. Particle motion through the resulting electric field gradients causes polarization of the suspended components, resulting in a body force that repels particle motion into increasing field gradients.