467969 3D Electrodes Integrated in Microfluidic Channels for Automated Single Cell Electrorotation Spectra Acquisition

Monday, November 14, 2016: 9:30 AM
Embarcadero (Parc 55 San Francisco)
Samuel Kilchenmann1, Marta Comino1, Ines R. Benmessaoud2, Pietro Maoddi1 and Carlotta Guiducci1, (1)Institute of Bioengineering, EPFL, Lausanne, Switzerland, (2)Physics, EPFL, Lausanne, Switzerland

3D electrodes integrated in microfluidic channels for automated single cell spectra acquisition

Samuel C. Kilchenmann, Iness R. Benmessaoud, Pietro Maoddi, Marta A. Comino, Carlotta Guiducci

Electrorotation is a known technique to extract electrical parameters of cells. As the rotational torque is highly dependent on the electric field strength, previous works focused on optimizing the shape of planar electrodes, to achieve uniform field strengths. Mostly, the optimization was performed only in 2D space and electrode distances above 100 μm were considered. While this strategy might lead to valid results in the electrode center, it is not suitable in cases of small electrodes, where the inter-electrode distance is in the range of the channel height, as the electrical fields will have a strong curvature and dependence on height. For this reason, in our lab, we focus on the application of 3D electrodes for electrorotation experiments. Such electrodes allow to achieve electric fields that have no dependence on the z-position and thus the rotation torque is constant over the full channel height. A direct consequence is that the signal amplitudes can be lowered, as for a given signal amplitude, 3D electrodes lead to a higher torque moment inside the microfluidic chamber, compared to a similar planar design. Ultimately 3D electrodes reduce the risk of cell and electrode damage, as they lead to lower electric field peaks and to lower thermal heating effects.

Furthermore, 3D electrodes were shown to lead to more stable particle trapping in microfluidic channels [1]. This can be used to achieve simultaneous trapping and rotation of particles inside microfluidic channels by applying simultaneous DEP and ROT signals [2]. For this reason, we developed a fabrication process to achieve 3D electrodes integrated in microfluidic channels [3] and we currently employ electrorotation experiments to extract complete electrorotation spectra of one single cells. The cells are injected into the system by microfluidic sample handling with a pressure driven system that allows for high control on flow and instantaneous flow stop. The latter in combination with the DEP trapping, allows for high precision in cell positioning. The good control over the electric field and the precise positioning of single cells by means of DEP lead to high control of experimental conditions and side effects such as clustering and particle-particle interactions can be reduced. For this reason, this system allows to extract a single cell electrorotation spectrum and to compare it to the rest of the population.

[1]          J. Voldman, M. Toner, M. L. Gray, and M. A. Schmidt, “Design and analysis of extruded quadrupolar dielectrophoretic traps,” J. Electrostat., vol. 57, no. 1, pp. 69–90, 2003.
[2]          A. Rohani, W. Varhue, Y.-H. Su, and N. S. Swami, “Electrical tweezer for highly parallelized electrorotation measurements over a wide frequency bandwidth.,” Electrophoresis, vol. 35, no. 12–13, pp. 1795–802, Jul. 2014.
[3]          S. C. Kilchenmann, E. Rollo, P. Maoddi, and C. Guiducci, “Metal-Coated SU-8 Structures for High-Density 3-D Microelectrode Arrays,” J. Microelectromechanical Syst., pp. 1–7, 2016.

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