VIETNAM NATIONAL UNIVERSITY, HANOI UNIVERSITY OF ENGINEERING AND TECHNOLOGY Nguyen Ngoc Viet FLUIDIC CHANNEL DETECTION SYSTEM USING A DIFFERENTIAL C4D STRUCTURE Branch : Electronics and Telecommunications Technology Major : Electronics Technology Code : 60520203 MASTER THESIS ELECTRONICS AND TELECOMMUNICATIONS TECHNOLOGY SUPERVISOR: Assoc. Chu Duc Trinh HA NOI - 2015 LUAN VAN CHAT LUONG download : add luanvanchat@agmail.com Acknowledgements I would first like to express my sincere gratitude towards my research supervisor, Assoc Prof. Chu Duc Trinh, who has helped me throughout my research work. The teacher was always by my side for interesting discussions and for giving some fruitful advice.
In addition, I would also like to thank T. Chu Duc’s research group members from MEMS Laboratory for their valuable inputs towards my research. And last but not least, I am grateful to the Faculty of Electronics and Telecommunications, UET- VNU, Hanoi for their willingness to offer help and suggestions whenever needed. Finally, I want to express the deepest gratitude to my family and my friends for their love and encouragements during my study.
Ha Noi, November 1st, 2015 Nguyen Ngoc Viet 2 LUAN VAN CHAT LUONG download : add luanvanchat@agmail.com Declaration I certify that the research described in this dissertation has not already been submitted for any other degree. I certify that to the best of my knowledge all sources used and any help received in the preparation of this dissertation has been acknowledged. Ha Noi, November 1st, 2015 Nguyen Ngoc Viet 3 LUAN VAN CHAT LUONG download : add luanvanchat@agmail.com Table of contents List of figures. 6 List of tables.
8 List of symbols and abbreviations. Background and Overview. THEORY OF CAPACITIVE SENSOR. Capacitive sensor applications.
Basic principles of C4D structure. Coplanar capacitive sensor in CMOS chip. DIFFERENTIAL C4D STRUCTURE FOR DETECTION OF OBJECT IN FLUIDIC CHANNEL. DC4D sensor for Conductive and Non-conductive Fluidic Channel.
Design and operation. DC4D simulations for non-conductive fluidic channel. Modelling of DC4D for conductive fluidic channel. 34 4 LUAN VAN CHAT LUONG download : add luanvanchat@agmail.
Fabrication and measurement setup. Developing DC4D sensor for microfluidic channel. RESULTS AND DISCUSSIONS. DC4D sensor system using U-shaped electrodes.
DC4D for non-conductive fluidic channel. DC4D for conductive fluidic channel. DC4D sensor system using microelectrodes. 57 5 LUAN VAN CHAT LUONG download : add luanvanchat@agmail.com List of figures Figure 2.
Charged parallel plates separated by an insulating medium. Examples of C4D designs used mostly for conduct metric detection. Design of a single C4D structure: (a) excitation and pick-up electrodes; (b) The equivalent circuits. Electric field formed between positive and negative electrodes for different pitch lengths, (l1, l2 and l3).
Sensing possibilities to detect various characteristic of samples: (a) sensing density, (b) sensing distance, (c) sensing texture, (d) sensing moisture. A simplified diagram of a capacitive sensing based LoC. Block diagram design of the DC4D fluidic sensor. The DC4D based on three-electrode configuration; (b) The equivalent diagram.
The interface of the structure simulation process using COMSOL Multiphysics. Simulated picture of the electric field norm when a plastic particle inside the fresh water channel. Simulated picture of the electric field norm when a tin particle inside oil channel. Capacitance change versus particle position inside a single C4D.
The equivalent circuit of the DC4D for conductive fluidic channel. The circuit diagram of the suggested structure. The equivalent circuit of the DC4D fluidic sensor. The single C4D admittance change when a particle moves though electrode inside conductivity solution.
Measurement system setup of the DC4D fluidic sensor. Proposal of a DC4D sensor. Cross-sessional view (a), side view (b), and DC4D sensor model (c). The fabricated chip.
Block diagram of the measurement system. Capacitance change versus particle position inside a single C4D, when the air bubble and tin particle move through machine oil channel, respectively. 43 6 LUAN VAN CHAT LUONG download : add luanvanchat@agmail. Single C4D capacitance change versus volume of the particles in oil channel.
The DC4D output voltage when a 4.18 l air bubble crosses electrodes in machine oil channel. The DC4D output voltage when a 4.18 l tin particle crosses electrodes in machine oil channel. The DC4D capacitance change when a 4.18 l air bubble crosses electrodes in machine oil channel. The DC4D capacitance change when a 4.18 l tin particle crosses electrodes in machine oil channel.
The DC4D output voltage response versus tin particle volume in oil channel. The DC4D output capacitance change versus tin particle volume in oil channel. The DC4D output voltage response when a plastic particle crosses electrodes: (a) water channel; and (b) salt solution channel. The DC4D admittance change when a plastic particle crosses electrodes: (a) water channel; and (b) salt solution channel.
The DC4D output voltage amplitude versus particle volume in salt solution and water. The DC4D output voltage amplitude versus particle volume in various concentration of salt solution. The DC4D output voltage change’s amplitude versus conductive fluidic resistivity. Velocity of investigated particle inside fluidic channel calculation.
Capacitance output of the DC4D sensor. Maximum differential capacitance output versus particle’s volume. Maximum differential capacitance output and electrical field distribution in 3e positions of object inside water fresh flow: (a), (b), (c): air bubble; (d), (e), (f): tin particle. 55 7 LUAN VAN CHAT LUONG download : add luanvanchat@agmail.com List of tables Table 3.
Geometry parameters of the proposed DC4D structure. Parameters of capacitive fluidic microsensor. The DC4D output voltage amplitude versus particle volume in salt solution and water. The DC4D output voltage amplitude versus particle volume in various concentration of salt solution.
50 8 LUAN VAN CHAT LUONG download : add luanvanchat@agmail.com List of symbols and abbreviations C4D : Capacitively Coupled Contactless Conductivity Detection (or C4D) C0 : Stray capacitance (F) Cs : Solution capacitance (F) Cw : Wall capacitance (F) CMOS: Complementary Metal-Oxide-Semiconductor CTCs : Circulating Tumor Cells DC4D : Differential Capacitively Coupled Contactless Conductivity Detection di : Size parameters of the pipe (i=1,2,3) (m) E : Electric field intensity (V/m) f : Ordinary frequency (Hz) FEM : Finite Element Method Gs : Solution conductance (S) g : Gap of adjacent electrodes (m) h : Micro-channel’s height (m) LoC : Lab on Chip Li , li : Size parameters of the electrodes (i=1,2,3) MEMS: Micro Electro-Mechanical Systems PCB : Printed Circuit Board PDMS : Polydimethylsiloxane Q : Magnitude of charge (C) Rs : Solution resistance (Ω) V : Voltage applied (V) w : Electrode’s width (m) Z : Equivalent impedance (Ω) : Relative permittivity (dielectric constant) : Admittance constant : Angular frequency (rad/s) 9 LUAN VAN CHAT LUONG download : add luanvanchat@agmail.com Summary Detection of the presence of strange particles in fluidic channels is important, due to their potential in chemical analysis, biology, pharmacology and especially in medical. The appearance of air bubble in the patient’s blood vessels is dangerous in case of the unpredictable of cerebral embolism can lead to instant death. The detection of strange cell in the blood vessel plays a crucial role in diagnosis or early detection of some diseases including cancer. In MEMS, the appearance of a particle in the microfluidic channel can affect significantly to the response of the flow such as the flow velocity, the fluidic pure quality.
Among the different physical techniques for detection of objects in fluidic channel such as optical, ultrasonic, electrical sensing based on contact and contactless mechanism, capacitive sensing emerged as the best technique. Capacitive sensor has been developed and applied in many field of technology due to simple fabricate and setup measurement, as well as minimization capability. Additionally, there are many advantages of capacitive sensors in micro fabrication and integration on systems. Capacitively coupled contactless conductivity detection (C4D) is a new detection technique has been developed in recent years and used mainly in capillary electrophoresis and microchip electrophoresis.
The characteristics of C4D detector are simple in structure, easy in miniaturization and integration, and free of electrodes contamination, which are common problems in an electrochemical detection. This thesis presents a novel design of a differential C4D (DC4D) structure based on three U-shaped electrodes which can apply to the fluidic channel detection systems at millimeter size. This structure consists of two single C4D with an applied carrier sinusoidal signal to the center electrode as the excitation electrode. The electrodes are directly bonded on the PCB with built-in differential amplifier and signal processing circuit in order to reduce the parasitic component and common noise.
The proposed structure can be used for both conductive and non-conductive fluidic channel. Simulations and experimental measurements are performed. Experimental results show that a good agreement with the simulation. Air bubbles and tin particles are pumped through electrodes for characterizing non-conductive fluidic case.
Plastic particles with various sizes are employed in the conductive fluidic configuration. Changes in both particles position and volume result in changes in the capacitance, the admittance or the output voltage between the electrodes are investigated. In the non- conductive fluidic channel, the output voltage and capacitance changes 214.39 mV 10 LUAN VAN CHAT LUONG download : add luanvanchat@agmail.com and 14 fF, respectively when a 4.18 µl tin particle crosses an oil channel. In conductive fluidic channel, the output voltage and admittance change up to 200 mV and 0.05 µS for the movement of a 4.63 µl plastic particle through 0.75% salt solution channel.
The measured results indicated the linear relation between the output voltage and the particle volume. Beside particle detection, this sensor system allows measuring velocity of the particle inside fluidic channel thanks to distance and travel time between the two single C4D structure. In addition, a microsensor based on DC4D structure is also designed, modeled, simulated and fabricated. The four-electrode capacitor is covered by thin PDMS protective layer.
Coplanar electrodes configuration is made of gold on glass substrate, which are arranged to form differential coplanar capacitor structures in order to achieve a high sensitivity and robust operation. The differential capacitance is changed when a micro particle (air bubble, particles or living cell for instance) crosses the microfluidic channel. The output capacitance changes versus object’s volume and position are simulated by using FEM tool. The simulation inspection reveals that the sensor can detect an object with diameter down to 10 µm in a 50×100 µm cross- section channel.
The capacitance change up to 0.3 fF when a 30 µm diameter air bubble and a same diameter tin particle move through in fresh water channel, respectively. A measurement setup was designed and implemented to monitor the capacitance change. The DC4D sensor is also fabricated by micro machining. The measurement with particles and living cell is in progress.
This proposed DC4D sensor can be used for detection of strange particle, air bubble in microfluidic flow or cell in medical devices and systems. This novel design can not only detect the present of an object but also volume, velocity, as well as electrical property (conduct/non-conduct) of the investigated object. 11 LUAN VAN CHAT LUONG download : add luanvanchat@agmail. Background and Overview The development of particle detectors practically starts with the discovery of radioactivity in the year 1896.
Henri Becquerel noticed that the radiation emanating from uranium salts could blacken photosensitive paper. Almost at the same time X rays, which originated from materials after the bombardment by energetic electrons, were discovered by Wilhelm Conrad Röntgen. The first detectors were used to detect radiation particles based on optical measurement. The trend of particle detection has shifted in the course of time from optical measurement to purely electronic means [9].
The particle detectors have found applications not only in nuclear and particle physics, but also in oil exploration, civil engineering, archaeology, environmental science, medicine, biology, etc. The methods and principles of these devices are also increasingly diversified and improved, with resolution and speed increasing. Nowadays, many advanced technologies in this evolving world are moving towards miniaturization of products. It resulted in the rapidly development of a new technology called MEMS (Micro Electro Mechanical Systems).