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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.

Development of compact and low-cost electronic circuits in the biosensor field is an essential demand. Especially, the design of noise reduction sections plays an important role in the measurement ...

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.

This paper presents the design, optimization, fabrication and characterization of a symmetrical two-axis tilt angle sensor. The sensor consists of a globe-calotte-shaped excitation electrode and tw...

A valveless microfluidic pump using a lead zirconate titanate (PZT) diaphragm actuated synthetic jet is developed and fabricated. For this present design, a valveless pump structure is developed in which the pump chamber is sealed on one side and connected to an emitting nozzle at another side. The design is simulated using the multiphysics approach and then successfully investigated with a prototype produced by a low-cost additive fabrication technique. The device's parameters, including the liquid pumping characteristics and the size of the PZT membrane, are optimized based on its desired performance. The developed device can be applied over a wide range of applications from micromixing to fluidic controlling.

This paper reports a study on developing of a protein detection biochip based on interdigitated array electrodes (IDAEs) capacitive immunosensor. The protein after being preconcentrated in a detection region will be selectively captured and detected by the capacitive immunosensor. Using electrical impedance spectroscopy operated at high-frequency in the range of 100 kHz–1 MHz, the capacitance of the gold electrode is determined and the antibody surface modification steps can be also monitored. The experiment results show the capacitance changes in accordance with the adding biochemical layer on gold electrodes for each step of the antibody surface modification. In particular, the total impedance operated at 1 MHz frequency has been seen to change from 2.1 kΩ of bare chip (before antibody surface modification) to 8 kΩ after antibody surface modification process while the serial capacitance is recorded to reduce steadily from 450 pF to 55 pF. Also, the efficiency of protein chip was investigated by implementing the measurement of 10 µM BSA with and without preconcentration process. The measurement results have shown the sensitivity increasing significantly after the protein is preconcentrated in this chip. The results demonstrate high efficiency of protein detection can be achieved by operating high frequency capacitive measurement on IDAEs capacitive immunosensor.

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.

This paper presents a design optimization and validation of a two-axis cylindrical capacitive tilt angle sensor. The proposed sensor includes of five electrodes symmetrically arranged surrounding a...

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.

A novel gyroscope using circulatory electro-hydrodynamics flow in a confined space is presented for the first time. The configuration of the new gyroscope includes three point-ring corona discharge actuators that generate ion flows in three separated sub-channels. The three ion flows then merge together when going through a nozzle of the main chamber entrance and create a jet flow. In the new configuration, the residual charge of ion wind flow is removed by a master-ring electrode located at one end of the main chamber. Under the effect of the angular speed of gyroscope, the jet flow is deflected and this deflection is sensed using hotwires. The results, which are consistently acquired by both the numerical simulation and experiment on our prototypes, demonstrate the repeatability and stability of the new approach. Since the ion wind can be generated by a minimum power, the present configuration-based device does not require any vibrating component. Thus, the device is robust, cost, and energy-effective.

Nanofibers has been recently received tremendous attention from researchers due to its advantages. Among the fabrication methods for nanofibers, electrospinning appears to be an intriguing technique, allowing the fabrication of nanofibers in a simple and inexpensive way. In this paper, we prepared and fabricated nanofibers using the electrospinning process with two polymers: gelatin and PVA. The process and the fabricated fibers were examined under scanning electron microscope. The effect of the polymeric concentration was also studied. The experimental results indicate that nanofibers were successfully fabricated, and higher polymer concentration leads to the uniformity of the fibers. In addition, the nanofiber mat with silver nanoparticles was successfully fabricated, opening the potential for medical applications of the fabricated fibers.

In this paper, we report on a gas gyroscope whose working principle is based on elec-tro-hydrodynamic flow generated by applying high voltage corona discharge, Coriolis acceleration and thermoresistive effects of sensing elements. Firstly, ionized air flow is created by applying high voltage between pin-ring electrodes as discharge-reference electrodes. When the sensor rotates, the ion wind is deflected because of Coriolis effect and four symmetric hot wires are used to recognize the direction change of ion wind. The simulation result confirms the deflection of air flow due to Coriolis force and the asymmetric thermal distribution of hot wires. The experiment result shows that the angular rate can be detected with a sensitivity of 4.7 µV/o/s.

A strain sensor with high flexibility using ionic liquid is proposed for sensing movements of human body. The resistance strain sensor is constructed from a silicon tube filled fully with a mixture of aqueous sodium chloride and glycerin sealed gold-coated electrodes. When an external force is applied to the sensor, the silicon tube deforms resulting in a change in the sensor resistance value. The proposed sensor was fabricated and experimentally characterized under several working conditions. Good performance was demonstrated in detecting the movement of human leg and fingers. The proposed simple sensor has high potential in wearable applications.

The paper reports the development of a particle precipitation based aerosol sampler using bipolar corona discharge ion winds with collected particles of minimized net charge. For the new approach, neutralized particles move towards a sampler under the effect of electric field and dual ion winds. Since there is no electrode or sampling chip installed inside the air-flow channel, impediments to airborne particle flow or ion winds are removed along the flow direction. In addition, the isolation of ion winds, which generate circuit, allows using various materials for the sampling chip including non-conductors and also protecting collected particles from any discharge ignition on the chip. The device mechanism is numerically simulated in OpenFOAM to study the electrofluidodynamic interaction of charged particles and bipolar ion winds. The efficiency of the new approach has been investigated by experiment with a maximum efficiency of 94%. The effects of flow rate, discharge voltage and electrode distances on the method are also evaluated.

The manipulation and detection of rare cells are important for many applications in early disease diagnosis and medicine. This study presents a dielectrophoresis (DEP) microfluidic enrichment platform combined with a built-in capacitive sensor for circulating tumor cell detection. The microchip is composed of a lollipop-shaped gold microelectrode structure under a polydimethylsiloxane chamber. A prototype of the device was fabricated using standard micromachining technology. With the proposed device, target cells (in this study, A549 non-small human lung carcinoma and S-180 sarcoma cell lines) are firstly guided toward the center of the working chamber via DEP forces. Then, the target cells are captured by an electrode immobilized by anti-EGFR, which has high affinity toward the target cells. After the cell concentration process, the differential capacitance is read to detect the presence of the target cells. Numerical simulations and measurement experiments were performed to demonstrate the high sensitivity of differential capacitive sensing. The obtained results show high sensitivity for S-180 cell detection (3 mV/cell). The proposed platform is suitable for rapid cancer diagnoses and other metabolic disease applications.

A fully packaged convective vortex gyrometer actuated by a PZT diaphragm is reported. The flow circulates at higher velocity after each actuating circle to form a vortex in the desired chamber. The vortex is characterized by hotwire anemometry. The device is initially designed based on a numerical analysis whose results are used to set up the experiment. The angular rate sensing of the device is successfully tested using a turntable. The technique is a potential solution to various applications related to inertial sensing and fluidic amplifier.

In this paper, a PZT synthetic jet that can function as both an efficient pumping and mixing device is developed. Compare with the conventional design where the practice of controlling the internal flow is undertaken by microvalves structure, this approach promotes the durability and allows the device to work with different liquids at high Reynold number without losing of backflow from the diffuser, therefore provides efficient mixing. The pumping performance is applicable for commercialized counterparts while the homogeneous medium was obtained at downstream in the experiments, which was further confirmed by simulation. Notably, the chaotic mixing feature of the device is also applicable for immiscible liquids with the micro-droplet formation result at the outlet.

A novel configuration of gyroscope using an electro-hydrodynamics flow circulating in a confined space is developed. The configuration includes three corona discharge based actuators to generate ionic flows inside three separated sub-channels which are connected to the main chamber. Ionic flows are merged together while they move through a nozzle installed at the main chamber entrance. After the merging phase, the conflated flow is diverged to move back to sub-channels where each accelerates at the discharge actuator. A master ring is installed at the end of the nozzle to remove any residual charge of the conflated ion flow. The ion flow velocity is measured using several hotwires installed in the main chamber. Since the configuration does not require any vibrating components, the present device is robust, cost-effective and consumes low power, hence, very potential in application of inertial sensing.

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.

In this study, a high flexibility strain sensor based on ionic liquid, which is a mixture of aqueous sodium chloride and glycerin pump in silicone tube, is developed. Gold-coated electrodes are inserted into both ends of the tube to make good contact with the liquid. When the silicone tube is affected by an external force, its geometry and electrical characteristics of the mixture inside the tube are changed, resulting in the change in the sensor resistance. The proposed sensor was fabricated and experimentally characterized. The 4-point resistance measurement based on alternating Howland current source was applied to the sensor for measuring the change in resistance of the sensor. A circuit board with PIC16F877A microcontroller is also developed for data acquisition and result display. Experimental results show that the sensor is highly flexible, i.e., can suffer from a stretch up to 50% with stable gauge factor in the range of 2.1 to 2.47. With its simplexes and high-flexibility, the proposed sensor has high potential to be applied to wearable and portable applications.

In the recent years, microfluidics droplet has attracted remarkable research attention and has been applied in a variety of fields such as emulsion, drug encapsulation, chemical mixing. This work presents a prototype for a flow-focusing microfluidics device which is utilized to produce micro-droplet. The simulations were carried out in order to study and validate the drop generation and the effect of different factors on this process. The results show that the droplet break up process was controlled by manipulating the flow rate and external electric field. The experiments were conducted and the droplets were successfully formed and observed. These results are the necessary foundation to produce desired droplets in doing experiments in the future.