Increasing operating frequency band of cytometric biosensor for single cell impedance characterization

摘要

This paper proposes to optimize the operating frequency band of a lab on a chip, based on bio-impedance spectroscopy for single cell. Bio-impedance allows to characterize low cells concentration or single cell by providing an electrical signature. Thus, it is necessary to perform impedance measurements up to several tens of mega-Hertz in order to extract the internal cell signature. In the case of a single cell, characterization is performed in a very small volume down to 1 pL. In the same time measured impedances increase up to hundreds of kilo-ohms. At frequencies above mega-Hertz, parasitic effects such as coupling capacitances could prevail over sample impedance and completely short-circuit it. To optimize the pass band, a complete model of a cytometric device was developed including coupling capacitances as a function of chosen materials. Simulation results prove the ability to increase the high frequency simply by optimizing track geometries and placement. This is done without any change of the sensing structure (microelectrodes design and microchannel). This assumption was obtained by measuring and comparing parasitic effects of our first sensors and the new optimized ones. Decrease of coupling capacitance by a factor higher than 10 was obtained allowing to perform characterizations in a wide frequency band.