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This review focuses on the theoretical concepts, electrode engineering, data analytics, and biomedical applications of electric and electrochemical microfluidic platforms, and highlights future directions for development.

Detection and counting of biological living cells in continuous fluidic flows play an essential role in many applications for early diagnosis and treatment of diseases. In this regard, this study highlighted the proposal of a biochip system for detecting and enumerating human lung carcinoma cell flow in the microfluidic channel. The principle of detection was based on the change of impedance between sensing electrodes integrated in the fluidic channel, due to the presence of a biological cell in the sensing region. A compact electronic module was built to sense the unbalanced impedance between the sensing microelectrodes. It consisted of an instrumentation amplifier stage to obtain the difference between the acquired signals, and a lock-in amplifier stage to demodulate the signals at the stimulating frequency as well as to reject noise at other frequencies. The performance of the proposed system was validated through experiments of A549 cells detection as they passed over the microfluidic channel. The experimental results indicated the occurrence of large spikes (up to approximately 180 mV) over the background signal according to the passage of a single A549 cell in the continuous flow. The proposed device is simple-to-operate, inexpensive, portable, and exhibits high sensitivity, which are suitable considerations for developing point-of-care applications.

The manipulation and separation of circulating tumor cells (CTCs) in continuous fluidic flows play an essential role in various biomedical applications, particularly the early diagnosis and treatment of diseases. Recent advances in magnetic bead development have provided promising solutions to the challenges encountered in CTC manipulation and isolation. In this study, we proposed a biomicrofluidic platform for specifically isolating human lung carcinoma A549 cells in microfluidic channels. The principle of separation was based on the effect of the magnetic field on aptamer-conjugated magnetic beads, also known as immunomagnetic beads, in a serpentine microchannel with added cavities (SMAC). The magnetic cell separation performance of the proposed structure was modeled and simulated by using COMSOL Multiphysics. The experimental procedures for aptamer molecular conjugation on 1.36 µm-diameter magnetic beads and magnetic bead immobilization on A549 cells were also reported. The lung carcinoma cell–bead complexes were then experimentally separated by an external magnetic field. Separation performance was also confirmed by optical microscopic observations and fluorescence analysis, which showed the high selectivity and efficiency of the proposed system in the isolation and capture of A549 cells in our proposed SMAC. At the flow rate of 5 µL/s, the capture rate of human lung carcinoma cells exceeded 70% in less than 15 min, whereas that of the nontarget cells was approximately 4%. The proposed platform demonstrated its potential for high selectivity, portability, and facile operation, which are suitable considerations for developing point-of-care applications for various biological and clinical purposes.

This study presents an efficient isolation of human lung carcinoma cell line (A549) platform by utilizing the proposal a serpentine microchannel with added cavities (SMAC) platform. The magnetic micro-bead isolation performance in proposed serpentine channel was simulated using COMSOL Multiphysics. The experimental procedures of aptamer molecular conjugation on magnetic microbeads affined to A549 cell line were also reported. The experimental results indicated that at the flow rate of 5 µL/s, the capture rate of human lung carcinoma cell reached above 70% in less than 15 min, whereas non-target cell capture rate was around 1.5%. The proposed platform shows its potential of high selectivity, portable, and simple-to-operate, which are suitable considerations for developing point-of-care applications in various biological and clinical purposes.

A sensor system based on a modified capacitively coupled contactless conductivity detection sensor is proposed and developed. The proposed system provides a passive and wireless readout technique, through which the conductivity of fluidic flow can be analyzed and foreign objects occurring in the fluidic flow can be detected. The proposed sensor system takes advantage of the series resonance principle and detects shifts in the resonance frequency and reflection coefficient to estimate the conductivity of the fluidic flow. In this paper, the working principle of the device is proposed and analyzed using a multiphysics simulation, and its performance is validated experimentally. The sensing performance is confirmed by measuring the conductivity of the fluidic media and the detection of foreign objects, such as air bubbles or water droplets, occurring in the flow. The influence of the distance between the inductors on the resonance frequency for different solution conductivities is also investigated and reported. The proposed sensor system shows its potential for use in various applications in biomedicine and chemistry, particularly in point-of-care applications, where the sensing chip can be easily set up for measurement and disposed of after use.

In the recent decades, droplet-based microfluidics has emerged as a promising research area which covers various applications in a broad spectrum of fields such as chemical reactions, drug discovery, molecule synthesis and cell biology. This study proposes the implementation of a microfluidic droplet generating prototype using the popular flow-focusing geometry. The proposed system is fabricated based on a rapid prototyping technique, which significantly simplifies the fabrication process, reduces the production cost and shortens the time-to-market as compared with traditional techniques. The functionalities and characteristics of the prototype were carefully verified by simulations and practical experiments. The obtained results showed that the generation of droplets could be precisely controlled by adjusting the flow rate ratio between the dispersed phase and the continuous phase.

This paper presents a dielectrophoresis (DEP) enrichment microfluidic platform with built-in antibody-based capacitive sensor for tumor rare cells detection. We take the advantages of the effective DEP actuation, the high selectivity property of antibody for rare cell immobilization, and the high sensitivity of differential capacitive sensing for quantitatively reading out, to produce advanced platform, toward single tumor cell detection for the rapid laboratory tests of cancers diagnoses and other metabolic diseases applications.

In this paper, we present a coplanar differential capacitively coupled contactless conductivity detection (CD-C4D) structure for the detection of tiny objects with dimension in micro scale. The differential capacitance changed due to the occurrence of an object in micro scale in is detected and used to recognize the presence as well as properties (i.e., electrical property and moving speed) of the object in fluidic flow. The experimental results and discussion in this paper can be generalized to any living cell or particle detection applications.