One usually uses DEP force to separate two kinds of particles using the difference in their dielectric properties. We develop a method of separation with multiple frequency dielectrophoresis which permits to separate bioparticles with very close dielectric properties while ordinary one-frequency methods fail.

Atomic Force Microscope (AFM) is an essential characterization and manipulation tool in nanoscience and engineering. It's operating method is based on the dynamical behavior of a microcantilever-sample system. The traditional research on AFM uses a one-mode model. My goal is to find the effect of higher modes on this nonlinear dynamical system. We analyze the forced dynamics of a microcantilever where the force on the tip is derived from the Lennard-Jones potential and thus depends on the displacement of the tip mass. Prior single-mode analysis showed complex nonlinear dynamics in some regimes. We present numerical and analytical results that confirm the necessity of inclusion of higher modes for the modeling of the AFM dynamics.

Electric fields are widely used to manipulate microparticles. Among various forms of electric fields we focus on dielectrophoresis (DEP) ; the motion of a particle due to the interaction between a non-uniform electric field and its induced dipole moment in the particle. The fields are applied to a suspension of particles by planar microelectrode structures. We study one particular design, the interdigitated electrode arrays with either two or four-phase signal. We worked on closed-form solutions of electric fields, dielectrophoretic forces and time-averaged forces for three cases : first, the case of a two-phase DEP electrode array with first-order approximate boundary condition, second, the case of a two-phase DEP electrode array with exact boundary condition and lastly the case of four-phase traveling wave (twDEP) electrode array with first-order approximate boundary condition. We discuss those results with a comparison to numerical solutions. One usually uses DEP force to separate two kinds of particles using the difference in their dielectric properties. We develop a method of separation with multiple frequency dielectrophoresis which permits to separate bioparticles with very close dielectric properties while ordinary one-frequency methods fail.