Micromachined impedance spectroscopy flow cytometer for cell analysis and particle sizing

Abstract

A new cytological tool, based on the microCoulter particle counter (microCPC) principle, aimed at diagnostic applications for cell counting and separation in haematology, oncology or toxicology is described. The device measures the spectral impedance of individual cells or particles and allows screening rates over 100 samples s(-1) on a single-cell basis. This analyzer is intended to drive a sorting actuator producing a subsequent cell separation. Size reduction and integration of functions are essential in achieving precise measurements and high throughput. 3D finite element simulations are presented to compare various electrode geometries and their influence on cell parameters estimation. The device is based on a glass-polyimide microfluidic chip with integrated channels and electrodes microfabricated at the length scale of the particles to be investigated (1-20 microm). A laminar liquid flow carries the suspended particles through the measurement area. Each particle's impedance signal is recorded by a differential pair of microelectrodes using the cell surrounding media as a reference. The micromachined chip and processing electronic circuit allow simultaneous impedance measurements at multiple frequencies, ranging from 100 kHz to 15 MHz. In this paper, we describe the microfabrication and characterisation of an on-chip flow-cytometer as the first building block of a complete cell-sorting device. We then discuss the signal conditioning technique and finally impedance measurements of cells and particles of different sizes and types to demonstrate the differentiation of subpopulations in a mixed sample.

Coplanar Electrode Layout Optimized for Increased Sensitivity for Electrical Impedance Spectroscopy

“…The optimized chip used in this work was designed with the same channel width as the conventional chip, except with a larger electrode area exposed to the channel as seen in Figure 1B. The limit of size detection of multi-frequency EIS is limited by the signal to noise ratio (SNR) of the chip [2]. The enlarged electrode area allows for a greater current between the electrodes and a greater current density in the constricted space between the electrodes, which is expected to lead to an improved SNR.…”

“…It probes individual particles suspended in a liquid by measuring the electrical impedance at several fixed frequencies simultaneously [2]. The multi-frequency detection allows for mapping of several properties of the sample such as size and structural composition [3,4].…”

Determining under‐ and oversampling of individual particle distributions in microfluidic electrophoresis with orthogonal laser‐induced fluorescence detection

“…Historically speaking, flow cytometry was the first technique to analyze individual subcellular particles [1], so it is not surprising that many of the first analyses of large populations of individual microparticles [2][3][4][5][6][7], cells [8,9], and subcellular particles [10] on microfluidic devices also used flow cytometry. Electrophoretic separation schemes have also been used since the first glass microfluidic devices were described by Manz et al [11] and Harrison et al [12,13] and they continue to be quite popular due to ease of application.…”

3D focusing of nanoparticles in microfluidic channels

“…One example of a particularly important application is the development of a flow cytometer on a chip [1][2][3][4][5][6][7][8][9][10]. For such systems to work efficiently, it is important to be able to confine the sample into a small, spatially well-defined volume, giving as small a probe volume as possible for the detector.…”

“…The concept of DEP is particularly attractive as it enables non-contact manipulation of particles such as cells in solution by high frequency electric fields [3], and characterisation of their passive dielectric properties [4][5][6][7][8]. If 3D electrode arrays are employed, interaction with walls or unspecific adsorption of particles may be avoided.…”