Single cell impedance analysis

D. Holmes, D. Pettigrew, C. H. Reccius, J. D. Gwyer, C. V. Berkel, J. Holloway, D. E. Davie and H. Morgan, Leukocyte analysis and differentiation using high speed microfluidic single cell impedance cytometry, Lab Chip, 9, 2881-2889 (2009). 

S. Gawad, T. Stm, N. G. Green and H. Morgan, Impedance spectroscopy using maximum length sequences Application to single cell analysis. Rev. Sci. Instr., 78, 054301 (2007). 

Andreasen et al. introduced a stack model that is suitable for prediction and analysis using EIS [45]. The typical output of such a measurement is a Nyquist plot, which shows the imaginary and real parts of the impedance of the measured system. The fuU stack impedance depends on the impedance of each of the single cells of the stack. Equivalent circuit models for each single cell can be used to predict the stack impedance at different temperature profiles of the stack. The results showed that a simple equivalent circuit model can be used to simulate the stack behavior. It was concluded that a more thorough characterization is required to predict the voltage dynamics under all operating conditions. 

Impedance Measurements of Cells, Figure 1 (a) Diagram showing the impedance analysis chip and a single cell flowing through the microfluidic... 

A. Valero, T. Braschler, P. Renaud, A unified approach to dielectric single cell analysis impedance and dielectrophoretic force spectroscopy, Lab on a Chip 10 (2010) 2216-2225. 

Compared with other methods, such as impedance spectroscopy, the current interrupt method has the advantage of relatively straightforward data analysis. However, one of the weaknesses of this method is that the information obtained for a single cell or stack is limited. Another issue is the difficulty in determining the exact point at which the voltage jumps instantaneously. 

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