Tung Thanh Bui

Piezo-resistive and thermo-resistance effects of highly-aligned CNT based macrostructures

Recent advances in assembling Carbon NanoTubes (CNTs) into macrostructures with outstanding properties, such as high tensile strength, high conductivity and porosity, and strong corrosive resistance, have underpinned potentially novel applications. For example, in advanced electronics, bioengineering and nanomechanics. This paper focuses on the development of (i) the piezoresistive polydimethylsiloxane–CNT (PDMS–CNT) composite membrane, and (ii) the thermo-resistive CNT hotwire using a technique of producing highly aligned CNT yarns and films. Our experimental results show that while PDMS–CNT films possess an outperformed gauge factor (10.7) compared with ones of CNT films in recent publications and several metals, a clear linear relationship of the resistance versus the temperature for a hotwire using CNT yarn is observed. Hence, the work supplies valuable evidence in the use of CNT films and yarns in several potential applications as thermal sensing elements and anemometric hotwires, respectively.

Jet flow focusing by corona discharge for fluidic application

This paper presents a study on a jet flow assisted by low net charge ion wind generated from bipolar corona setup, adding momentum to the bulk flow directed alongside the electrodes and focused in the middle of interelectrode space. It was confirmed that with only 27.1 mW of consumed discharge power, the corona helped to focus and increased the flow peak velocity up to 71.6%, i.e., from 1.41 m/s to 2.42 m/s. Because the generated air flow remains neutral, this work can contribute to the development of multi-axis fluidic inertial sensors, fluidic mixing and analysis with space constraints and/or where neutralized discharge process is required.

Dielectrophoresis Microfluidic Enrichment Platform with Built-In Capacitive Sensor for Rare Tumor Cell Detection

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 compact microfluidic chip with integrated impedance biosensor for protein preconcentration and detection

In this study, a low-cost, compact biochip is designed and fabricated for protein detection. Nanofractures formed by self-assembled gold nanoparticles at junction gaps are applied for ion enrichment and depletion to create a trapping zone when electroosmotic flow occurs in microchannels. An impedance measurement module is implemented based on the lock-in amplifier technique to measure the impedance change during antibody growth on the gold electrodes which is caused by trapped proteins in the detection region. The impedance measurement results confirm the presence of trapped proteins. Distinguishable impedance profiles, measured at frequencies in the range of 10-100 kHz, for the detection area taken before and after the presence of proteins validate the performance of the proposed system.

Ionic JET flow in a circulatory miniaturized system

This paper reports a novel device for generating circulatory jet flow using bipolar discharge configuration. This arrangement, in which two electrodes serve as mutual emitters and reference defining the electric field, allows to generate simultaneously ionic wind with opposite charge, thus the ion flow is self-neutralized while keeping the momentum in desired direction. In order to prevent system from sparking over, between the two parallel electrodes is installed one millimetre thick polypropylene wall. Experiment and simulation has shown that the air flow is successfully circulated in the confined device with peak velocity of 2 m/s while consuming only 33 mW.

A Robust Two-axis Tilt Angle Sensor Based on Air/Liquid Two-phase Dielectric Capacitive Sensing Structure

ABSTRACT This paper presents the design, fabrication, and characterization of a two-axis tilt angle sensor based on the air/liquid two-phase dielectric capacitive sensing structure. The sensor consists of five electrodes, one serves as the exciting electrode and two pairs of electrodes as sensing ones, which are arranged at identical positions surrounding a glass cylinder tube. The glass cylinder tube is partly filled with dielectric liquid to form the air/liquid two-phase dielectric medium. Based on this arrangement, the proposed sensor can detect roll and pitch angles, simultaneously. A computational simulation and experimental measurements are performed to study the performance of the sensor. The numerical simulation is carried out with a finite element analysis using COMSOL. A prototype of the sensor was fabricated, and its performance was evaluated. The tilt angle sensor was employed on a printed circuit board with a conditioning circuit, consisting of a sine wave generator, pre-amplifiers, rectifiers, and low pass filters. The experiment results confirmed that the roll angle detection has a linear range in the range of −60° to +60° with non-linearity error of 6.6%. The sensitivity and resolution in this range are 18.2 mV/° and 0.55°, respectively. For pitch angle detection, the linear range is −16° to +16° with non-linearity of 10%, and sensitivity and resolution of 58.2 mV/° and 0.17°, respectively.

A symmetrically arranged electrodes for corona discharge anemometry

This paper presents a novel anemometry based on bipolar corona discharge probe with symmetrically arranged parallel electrodes, which is potentially applicable for in-situ measurement. With the proposed configuration, under the existence of the airflow, the decomposed gas is redistributed towards the downstream electrode, and changes the current-voltage characteristics of the system. Experimental study on the anemometry characteristics demonstrates the possibility of measuring a wide range of air flow rate/ flow velocity, i.e., up to 80 l/m.

Dielectrophoresis enrichment with built-in capacitive sensor microfluidic platform for tumor rare cell detection

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.

A compact exclusion-enrichment microfluidic chip with integrated impedance biosensor for lowconcentration protein detection

This paper presents a design of a compact system for low concentration protein detection based on an effectiveness concentrator which is relied on exclusion-enrichment effect (EEE) and a highly sensitivity lock-in impedance measurement technique. Experiment results suggested that protein concentration of down to sub-nanomolar can be detected by the proposed system.

Coplanar differential capacitively coupled contactless conductivity detection (CD-C4D) sensor for micro object inside fluidic flow recognization

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.