Download Lab-on-a-chip Microfluidic System.

Single particle trapping and characterization
using dielectrophoretic particle trap
Tae Joon Kwak, Hwangjae Lee, Jörg C. Woehl, Woo-Jin Chang
Department of Mechanical Engineering, Chemistry and Biochemistry, and School of Freshwater Sciences,
University of Wisconsin-Milwaukee
INTRODUCTION
• Recent progress in micro- and nano-technology enables the development of
various methods and devices to manipulate molecules such as electrophoresis,
dielectrophoresis (DEP), etc.
• Separation and characterization of specific particle and cell is important for a
wide range of applications in pharmaceutical companies or cancer cell research.
• We have applied AC-based DEP to capture and separate vast number of particles
and cells in single particle level.
• The electrical properties of the particles can be determined by combining single
particle manipulation and further analytical techniques.
• All traps in the array supply the identical electric field distribution to provide the
same operating condition on any particles in the sample solution.
MATERIALS AND METHODS
Dielectrophoresis (DEP)
• A dielectric particle placed in an electric field becomes electrically polarized as a
result of partial charge separation
• The charge separation leads to an induced dipole moment. In a non-uniform
electric field, the particle experience dielectrophoretic force.
r
E
–
–
m –
Re[K] –
radius of particle
electric field
permittivity of medium
 *p   m*
Clasius-Mossotti Factor where K 
 *p  2 m*
*   j


σ = conductivity of electric field
ω = angular frequency of electric field
Dielectrophoresis (DEP)
r – radius of particle ,
E – electric field,
Re[K] – Clasius-Mossotti Factor where
m
– permittivity of medium
 *p   m*
K *
 p  2 m*
• The direction of the force is determined by the K, as known as the Clausius-Mossoti factor.
• If a suspended particle has higher polarizability than the medium, the DEP force will push
the particle toward regions of higher electric field (positive DEP).
• On the other hand, if the medium has a higher polarizability than the suspended particle, the
particle is driven toward regions of low field strength (negative DEP).
Numerical Simulation
• The trap geometry is designed using numerical simulation to trap single particles.
Circular shaped traps are designed for the generation of omni-directional negative
dielectrophoretic forces.
z
y
• Numerical analysis is also used to calculate the dielectrophoretic force acting on
each particle by the voltage applied to the electrode.
Lab-on-a-chip Microfluidic System.
• The Lab-on-a-chip microfluidic device was fabricated through micro
photolithography process.
Lab-on-a-chip Microfluidic System.
RESULT AND DISSCUSSION
• The polystyrene particles in the solution flowing in
the microchannel moved freely along the flow.
Individual particle was trapped in each trap by the
trapping force of the DEP force with the aid of the
electric field formed around the trap.
• In a trap array, the electric field distribution around
each dielectrophoretic trap capturing a particle does
not vary from trap to trap. Particles with the same
physical and electrical properties are captured in all
traps under certain, well-defined conditions.
CONCLUSION
• This study will advance the rapid isolation and identification of the molecules
and micro- and nano-particles, such as cells, bacteria and DNA in single molecule
level, by simultaneous manipulation of large number of the particles under
identical condition.
Thank You