Introduction

The definition of particle electromechanics offered in Chapter 1, Section 1.2, is very broad, precluding any possibility of definitive treatment in a single volume. Accordingly the scope of this book is restricted primarily to field–particle interactions involving (i) uncharged, lossy, dielectric and electrically conductive particles with AC and DC electric fields and (ii) magnetizable, electrically conductive particles with AC and DC magnetic fields. The particle electromechanics of interest here are a consequence of either the field-induced polarization of dielectric particles or the field-induced magnetization of magnetic particles. The forces and torques governing particle behavior result from the interaction of the dipole and higher-order moments with the field.

Electromechanics of particles

Two distinct types of electromechanical interactions may be identified: imposed field and mutual particle interactions. Imposed field interactions reign when a single particle, or an ensemble of noninteracting particles, is influenced by an externally imposed field. Examples include the dielectrophoretic force or the alignment torque exerted on an isolated particle. Here, it is customary to assume that the particle does not influence the field, though such an assumption is not always justified. Mutual particle interactions occur where particles are so closely spaced that the local field of a particle influences its neighbors. For particles in close mechanical contact, mutual interactions can be very strong, leading to significant changes in the equilibrium structure of particle ensembles (e.g., chain formation and cooperative electrorotation), as well as strong cohesive forces.

For the purpose of convenience in presentation, this monograph is organized into sections on imposed field interactions (Chapters 2 through 5) and mutual interactions (Chapters 6 and 7).