Continuous Cell Characterization and Separation by Microfluidic Alternating Current Dielectrophoresis

Abstract

A novel alternating current (ac)-dielectrophoretic (DEP) microfluidic chip for continuous cell characterization and separation is presented in this paper. To generate DEP forces, two electrode-pads are embedded in a set of asymmetric orifices on the opposite sidewalls to produce the nonuniform electric fields. In the vicinity of a small orifice, the cells experience the strongest nonuniform gradient and are drawn toward it by the positive DEP forces, while the cells experiencing a negative DEP force are repelled away and move toward the large orifice. The DEP behaviors of yeast cells in suspending media with different ionic concentrations, i.e., different electrical conductivities, and over a large range of the ac electric field frequency were investigated. Furthermore, the lateral migrations of yeast cells as a function of the ac frequency were measured. The trends of measured lateral migrations of yeast cells are similar to the corresponding Clausius−Mossotti (CM) factors. In addition, by adjusting the frequency and strength of the ac electric field, the continuous separation of live and dead yeast cells as well as the yeast cells with targeted diameter and dielectric property can be easily achieved. This is the first time that the measurement of ac-DEP lateral migration of yeast cells in solutions with different electrical conductivities as a function of the applied frequency in a microfluidic chip was reported. This ac-DEP system provides a method to characterize the crossover frequency of the specific cells and manipulate the targeted cells.

Recent advances in dielectrophoresis‐based cell viability assessment

“…A similar reservoir‐based DEP device was also proposed recently (Fig. 6C) . There was an asymmetric orifice placed on one side of the main channel.…”

“…(C) Cell separation by small orifice‐based DEP. Adapted with permission from , © 2019 American Chemical Society. (D) Continuous field‐flow cell separation with 3D electrodes.…”

Biosensors Based on Mechanical and Electrical Detection Techniques

“…Dielectrophoresis (DEP) is a technique that utilises an inhomogeneous electric field to move particles according to their polarisability [ 185 , 186 ]. It can be an effective, high-throughput method for manipulating different cell populations through differences in their polarisability [ 187 , 188 ]. It is a non-invasive technique, and may be used without detriment to the cells under examination [ 189 ].…”

“…This means that DEP can be used with an alternating current (AC). This is important for the application of DEP to cells, as the capacitive effects of the cell membrane are negligible at higher frequencies [ 140 ], enabling separation of cell populations based not on the external media, but on the size of the cell and conductivity of the cell cytoplasm [ 188 ]. This has been utilised by Modarres et al in a “frequency hopping” DEP to capture cells at one frequency and selectively release the unwanted cells at another [ 211 ], as shown in Figure 17 .…”

High-Sensitivity in Dielectrophoresis Separations

“…Rather than limited by proximity to a planar interdigitated electrode array on a single channel surface, placing potential and ground on opposite sides of the channel allows the DEP force to be applied further in to the fluid domain. Extending the application, electrodes on either sidewall have been developed to achieve lateral separation of a number of analytes [14,52,53]. By changing the distance between electrodes the field magnitude can be spatially mapped, and cell separation can be tuned even further, improving sensitivity and allowing for either batch or continuous separations.…”