Measurement of the Imaginary Part of the Clausius-Mossotti Factor of Particle/Cell via Dual Frequency Electrorotation.

A simple and inexpensive method using planar electrodes was proposed for the measurement of the imaginary part of the Clausius-Mossotti factor, K i , of particle/cell for electrorotation (ER) and travelling wave dielectrophoresis (twDEP). It is based on the balance between the dielectrophoretic and viscous torques on a particle undergoing ER subject to dual frequency operation in an ER chamber. A four-phase ac voltage signal with a given frequency is applied for generating ER for measurement, and another two-phase signal is applied at a selected frequency for generating a negative dielectrophoretic force for confining the particle motion, instead of using laser tweezer or three-dimensional electrodes in the literature.

Measurement of the real part of the Clausius-Mossotti factor of dielectrophoresis for Brownian particles.

A method is proposed for measuring the real part of the Clausius-Mossotti factor ( ) of dielectrophoresis for Brownian particles based on a solution of the Smoluchowski equation using a designed polydimethysilloxane microchannel with planar hyperbolic electrodes on its glass substrate. An approximate two-dimensional spring-like dielectrophoretic force is generated in the device, and the data necessarily measured is the time evolution of the in-plane particle displacement undergoing confined Brownian motion. Validity of the measurement was checked against the zeta potentials in the literature based on the classical theory of surface conductance using polystyrene particles of size of one micron.

A Continuous Flow-through Microfluidic Device for Electrical Lysis of Cells.

In contrast to the delicate 3D electrodes in the literature, a simple flow-through device is proposed here for continuous and massive lysis of cells using electricity. The device is essentially a rectangular microchannel with a planar electrode array built on its bottom wall, actuated by alternating current (AC) voltages between neighboring electrodes, and can be incorporated easily into other biomedical systems. Human whole blood diluted 10 times with phosphate-buffered saline (about 6 10 cells per mL) was pumped through the device, and the cells were completely lysed within 7 s after the application of a 20 V peak-to-peak voltage at 1 MHz, up to 400 μL/hr.

Three dimensional electrode array for cell lysis via electroporation.

Microfabricated devices for cell lysis have demonstrated many advantages over conventional approaches. Among various design of microdevices that employ electroporation for cytolysis, most utilize Ag/AgCl wires or 2D planar electrodes. Although, simple in fabrication the electric field generated by 2D electrodes decays exponentially, resulting in rather non-uniform forcing on the cell membrane.