V11_Dielectrophoresis: Introduction to Polarizable Particles in Nonuniform Electric Fields

What is the relationship between the electric flux density ($\vec{D}$) and the electric field strength ($\vec{E}$) in a vacuum?

$\vec{D} = \epsilon_0 \vec{E} + j \vec{B}$
$\vec{D} = \epsilon_0 j \vec{E}$
$\vec{D} = \frac{1}{\epsilon_0} \vec{E}$
$\vec{D} = \epsilon_0 \vec{E}$ (correct)

What is the value of the permittivity of free space ($\epsilon_0$) in SI units?

8.854187 × 10^-6 F/m
8.854187 × 10^-12 F/m (correct)
8.854187 × 10^-3 F/m
8.854187 × 10^-9 F/m

In the context of dielectrophoresis, what is the primary mechanism that generates a force on a polarizable particle in a non-uniform electric field?

The electric field directly exerts a force on the particle due to its charge.
The electric field induces a dipole moment in the particle, and the non-uniform field generates a net force on the induced dipole. (correct)
The electric field induces a current in the particle, and the non-uniform field generates a force due to the induced current.
The electric field polarizes the surrounding medium, and the non-uniform polarization generates a force on the particle.

What is the imaginary unit ($j$) used for in the context of complex permittivity?

To represent the imaginary component of permittivity, which accounts for energy dissipation. (B) Signup and view all the answers

Which of the following statements about microfluidic systems is true?

Microfluidic systems are typically designed to handle fluid volumes on the order of microliters or less. (C) Signup and view all the answers

What is the primary advantage of using dielectrophoresis in microfluidic systems?

It allows for the precise control and manipulation of particles without the need for physical contact. (D) Signup and view all the answers

In the context of dielectrophoresis, what is the significance of the imaginary part of the Clausius-Mossotti factor ($f_{CM}$)?

It represents the phase shift between the induced dipole moment and the applied electric field. (D) Signup and view all the answers

In the context of electrorotation, what is the primary cause of the torque that induces particle rotation?

The interaction between the induced dipole moment and the applied electric field phase. (D) Signup and view all the answers

What is the primary reason for applying a traveling wave to the electrodes in electrorotation?

To induce a phase shift in the applied electric field, causing particle rotation. (D) Signup and view all the answers

Which of the following statements best describes the relationship between dielectrophoresis and electrorotation?

Electrorotation is a special case of dielectrophoresis, where the applied electric field is rotating. (C) Signup and view all the answers

In the context of microfluidic systems, what is the primary advantage of using dielectrophoresis for particle manipulation?

It allows for precise control over the position and rotation of particles without physical contact. (D) Signup and view all the answers

In the context of dielectrophoresis, what is the significance of the complex permittivity of the particle and the surrounding medium?

All of the above. (D) Signup and view all the answers

What is the mathematical expression for the dielectrophoretic force $F_{DEP}$?

$F_{DEP} = 2\pi r^3 \epsilon_m \text{Re}\left[\frac{\epsilon_p^* - \epsilon_m^}{\epsilon_p^ + 2\epsilon_m^*}\right] \nabla E^2$ (D) Signup and view all the answers

Why are AC fields preferred over DC fields for dielectrophoresis?

All of the above (D) Signup and view all the answers

What is the significance of the imaginary unit $j$ in the complex permittivity $\epsilon^*$?

The imaginary unit $j$ represents the imaginary part of the complex permittivity. (D) Signup and view all the answers

What is the relationship between the root-mean-square (RMS) electric field $E_{rms}$ and the dielectrophoretic force $F_{DEP}$?

$F_{DEP} \propto E_{rms}^2$ (C) Signup and view all the answers

What is the primary challenge in applying dielectrophoresis to very small particles?

Both (a) and (b) (A) Signup and view all the answers

Which of the following is a common application of dielectrophoresis in microfluidic systems?

Separation of different cell types (C) Signup and view all the answers