A high-throughput flow cytometry-on-a-CMOS platform for single-cell dielectric spectroscopy at microwave frequencies

Abstract

This work presents a microfluidics-integrated label-free flow cytometry-on-a-CMOS platform for the characterization of the cytoplasm dielectric properties at microwave frequencies. Compared with MHz impedance cytometers, operating at GHz frequencies offers direct intracellular permittivity probing due to electric fields penetrating through the cellular membrane. To overcome the detection challenges at high frequencies, the spectrometer employs on-chip oscillator-based sensors, which embeds simultaneous frequency generation, electrode excitation, and signal detection capabilities. By employing an injection-locking phase-detection technique, the spectrometer offers state-of-the-art sensitivity, achieving a less than 1 aFrms capacitance detection limit (or 5 ppm in frequency-shift) at a 100 kHz noise filtering bandwidth, enabling high throughput (>1k cells per s), with a measured cellular SNR of more than 28 dB. With CMOS/microfluidics co-design, we distribute four sensing channels at 6.5, 11, 17.5, and 30 GHz in an arrayed format whereas the frequencies are selected to center around the water relaxation frequency at 18 GHz. An issue in the integration of CMOS and microfluidics due to size mismatch is also addressed through introducing a cost-efficient epoxy-molding technique. With 3-D hydrodynamic focusing microfluidics, we perform characterization on four different cell lines including two breast cell lines (MCF-10A and MDA-MB-231) and two leukocyte cell lines (K-562 and THP-1). After normalizing the higher frequency signals to the 6.5 GHz ones, the size-independent dielectric opacity shows a differentiable distribution at 17.5 GHz between normal (0.905 ± 0.160, mean ± std.) and highly metastatic (1.033 ± 0.107) breast cells with p ≪ 0.001.

Positional dependence of particles and cells in microfluidic electrical impedance flow cytometry: origin, challenges and opportunities

“…Besides their use as particle and cell sorting actuation means 87 , hydrodynamic flow focusing methods have been used for a long time together with impedance-based particle counting and/or characterization in microfluidic devices [88][89][90][91][92][93][94] . Such methods enable the control of the particle path through the channel.…”

A Scalable and Low Stress Post-CMOS Processing Technique for Implantable Microsensors

“…), including systems-on-chip. Examples range from MEMS (microelectromechanical) integrated systems [ 1 , 2 ] to microfluidic devices [ 3 , 4 , 5 , 6 ], and bio/chemical sensors [ 7 , 8 , 9 , 10 , 11 ]. Among those applications, the development of wireless microscale neural implants using CMOS has been explored as one approach for next-generation brain–machine interfaces (BMI) by several groups [ 12 , 13 , 14 , 15 , 16 , 17 , 18 ].…”

“…For this problem, stable and biocompatible alternative materials such as gold (Au), platinum–iridium alloy, and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) are attractive to provide long-term reliability of the electrode–tissue interface and electrode–electrolyte impedance optimization [ 19 , 20 , 21 , 22 , 23 , 24 ]. One post-CMOS strategy has made use of the sacrificial carrier substrate accompanying the bare die that holds the individual microdevices, using deep-etched silicon, silicon oxide substrate [ 25 , 26 , 27 ], or rigid polymer [ 5 , 6 , 28 , 29 , 30 ]. However, in the case of using the silicon-based carrier substrate, the size variance of chips, generated during a dicing process, can result in discontinuity on the surface of chip-to-carrier assembly.…”

Broadband Electrical Sensing of a Live Biological Cell with In Situ Single-Connection Calibration

“…With emerging broadband electrical sensing of a single biological cell [ 1 ], fast, accurate, and in situ broadband electrical calibration is needed for incorporating the sensing technique in a high-throughput cytometer [ 2 ]. In particular, the calibration is needed for deembedding the measured scattering ( S ) parameters to reference planes as close to the cell as possible [ 3 , 4 , 5 ].…”