Introduction to Adaptive Lenses

Chapter 4

Dielectrophoretic Lens

4.1 Introduction

It is well known that when a small particle with net electric charge is placed in a homogeneous electrostatic field, the particle immediately bears a force. This force is called an electrostatic force. If the particle is neutral (dielectric) with balanced positive and negative charges, the net electrostatic force is zero. However, when such a dielectric particle is placed in a nonuniform electric field, it instantly bears a force, called a dielectrophoretic force. Dielectrophoresis (DEP) is a phenomenon that occurs when a neutral particle is placed in an electric field that is spatially non-homogenous. The term DEP was first introduced by Herbert Pohl in the early 1950s (1). In his book, he defined dielectrophoresis as the translational motion of neutral matter caused by polarization effects in a nonuniform electric field. Since then, numerous works have been done and various microfluidic devices have been developed based on the operation mechanism of DEP effect.

In the past years, DEP has been applied to the following subjects:

1. Manipulation of Particles DEP force has been used to manipulate microparticles, nanoparticles, and, in particular, biological cells, viruses, and proteins (2, 3). For example, the separation of viable and nonviable yeast cells (4), the separation of mixtures of Bacillus subtilis, Escherichia coli, and Micrococcus luteus bacteria (5), and the separation of human breast cancer cells from blood (6).

2. ...