Lab-on-a-chip technology for single cell manipulation and characterization using electrical methods

In recent years, considerable attention has been paid to miniaturized and integrated mechanical, acoustic, optical, electronic, magnetic and fluidic devices for biochemical and biomedical applications. This field is known as Micro Total Analysis System (?TAS) or Lab-On-a-Chip (LOC) technology. This paper presents theoretical and experimental developments of single cell manipulation and characterization in the microfluidic systems, in which cells can be handled, trapped, separated, focused, sorted and identified using electrical methods. For cell manipulation, AC electrokinetic techniques are used, such as dielectrophoresis (DEP), travelling wave dielectrophoresis (twDEP) and electrorotation (ROT). The electrical force/torque on the cells due to the dipole-electric field interaction results in the translational motions of the cells. A microfluidic cytometer has been designed to focus and measure single cells in the microchannel with multiple electrodes integrated. An analytical model has been developed to describe the movements of cells by the dielectrophoretic focusing electrodes using negative DEP. Due to the negative DEP force; the cells are focused into the central stream within the channel, where the intensity of the electric field is minimum. After focusing, the dielectric properties of single cells are probed by the measurement electrodes using electrical impedance spectroscopy (EIS) as a high throughput, non-invasive and label-free technique. The information of the size and internal properties of the individual cells (i.e. cell membrane capacitance and cytoplasm conductivity) can be characterized in the different frequency decades. A novel multi-frequency impedance spectroscopy using maximum length sequences (MLS) has been developed to obtain the broad-band spectrum of single cells with high frequency resolution within a short time window (ms). These electrical methods have a wide range of biotechnological and biomedical applications