Differential C4D sensor for conductive and non conductive fluidic channel

Microsyst Technol DOI 10.1007/s00542-015-2586-4 TECHNICAL PAPER Differential C4D sensor for conductive and non‑conductive fluidic channel Nguyen Dac Hai1 · Vu Quoc Tuan2 · Do Quang Loc3 · Nguyen Hoang Hai4 · Chu Duc Trinh5  Received: 12 May 2015 / Accepted: 29 May 2015 © Springer-Verlag Berlin Heidelberg 2015 Abstract  This paper presents a novel design of a differential C4D (DC4D) sensor based on three electrodes for both conductive and non-conductive fluidic channel 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 In the non-conductive fluidic channel, the output voltage and capacitance changes 214.39 mV and 14 fF, respectively when a 3.83 μl tin particle crosses an oil channel In conductive fluidic channel, the output voltage and admittance change up to 300 mV and 0.07 μS for the movement of a 4.88 μl plastic particle through channel Moreover, the voltage change of this sensor is linear relation with the volume of investigated particle This sensor also allows measuring velocity of particle inside fluidic channel and resistivity of the conductive fluidic * Chu Duc Trinh trinhcd@vnu.edu.vn Posts and Telecommunications Institute of Technology, Hanoi, Vietnam Institute of Applied Physics and Scientific Instrument, Vietnam Academy of Science and Technology, Hanoi, Vietnam University of Science, Vietnam National University, Hanoi, Vietnam Nano and Energy Center, Vietnam National University, Hanoi, Vietnam University of Engineering and Technology, Vietnam National University, Hanoi, Vietnam 1 Introduction Fluidic flow detection has been developed for many practical applications in different areas like pharmaceutical, chemical analysis, oil industry, and so on There are some fundamental methods which have been applied for fluidic flow detection such as optical, ultrasonic, electrical sensing based on contact and contactless mechanisms Fluidic channel sensor can be used electrical conductivity parameter of material and channel geometry based on the direct contact technique (Gong 2008) In this technique, the detection electrodes are directly in contact with the fluidic, liquid or electrolyte solution The polarization effect and electrochemical erosion effect in the solution or the electrodes are unavoidable in this way Besides, the contamination of the electrodes usually causes errors in conductivity measurement These disadvantages limit the practical applications of the conventional contact conductivity detection techniques (Huang et al 2012) The capacitive contactless sensor structures are developed in order to avoid the direct contact technique issues (Gong 2008; Opekar et al 2013; Wang et al 2013; Zemann et al 1998) Capacitive sensor structures as the contactless mechanism are often used to measure the phase flow detection such as air–water–oil (Quoc et al 2015; Demori et al 2010; Strazza et al 2011) However, the sensor sensitivity of the capacitive configuration is low in case of high conductivity liquid due to the much small resistance value of the conductive fluidic channel in comparison with the sensor capacitance (Strazza et al 2011) Jaworek et al presents a high frequency capacitance sensor to solve the conductive effects of water using an 80 MHz oscillator However, that device requires an extremely short electrodes for a quasi-local measurement and a rather complicated circuit (Jaworek et al 2004) 13 The capacitively coupled contactless conductivity detection (C4D) sensor structure is a conductivity detection technique, which was proposed by Fracassi da Silva et al and Zemann et al independently in 1998 (Zemann et al 1998; da Silva and Lago 1998) This kind of technique is applied in many areas and has brought an undeniable advantage into detection and measurement field The C4D structures consist of two electrodes separated by a gap Based on the conductivity of liquid, the flow will transmit the signal from an exciting electrode through the dielectric of a pipe and bring the information of the liquid’s conductivity to the pick-up electrode (Huang et al 2012; Wang et al 2013; Zemann et al 1998; Zhang et al 2012, 2013; Kuban and Hauser 2008, 2011; Liu et al 2013; Kuban et al 2002) C4D can be used for detecting oil in the water and impurities in tap water (electrical conductivity liquid) Hence, this application can become an excellent method in solving problems in the oil and gas industry (Demori et al 2010) Moreover, up to date, the C4D technique is studied and used in the research field of Analytical Chemistry for ion concentration/conductivity detection in the capillary and the conductivity of fluidic channels (Huang et al 2012) Another useful application of this technique is estimating the velocity of the conduct fluidic flow and measurement of bubble velocity in gas–liquid two-phase flow in millimeter-scale pipe, which is a fundamental problem existing in many industries, such as chemical, pharmaceutical, petroleum, energy and power engineering (Wang et al 2013) Application based on C4D technique in detecting impurities and estimating their velocity in fluidic channel is researched and developed by many research groups despite of its difficulties and limitations (Kuban and Hauser 2008, 2011; Solinova and Kasicka 2006) There are several measurement methods that are developed to against these difficulties and limitations of the conventional C4D technique A grounded shield between the excitation electrode and the pick-up electrode can be used to prevent stray capacitance (Kuban and Hauser 2004a, b, 2008; Gas et al 2002) or take advantage of parallel resonance effect to remove the influence of stray capacitance and coupling capacitances (Shih et al 2006) Some designs use this resonator method to measure the conductivity and flow detection (Huang et al 2012; Wang et al 2012) but in that case, the permittivity could not be recognized, for example the case of full oil or the air inside pipe This paper employs a differential amplifier to avoid the above difficulties with a sensor system including three U-shape electrodes on the top of a printed circuit board (PCB) in order to reduce the parasitic capacitance and increase the sensitivity not only in the conductivity liquid but also in the non-conductivity liquid This DC4D structure consists of two sensing electrodes and one exciting 13 Microsyst Technol Particle Cylinder R0 580 KHz sine wave AC Source Differential amplifier LPF V in V out R0 Reservoir Fig. 1  Block diagram design of the DC4D fluidic sensor Excitation electrode Pick - up electrode AC source io fluid flow Signal output (a) C0 Cw R1 Rs XC (b) Fig. 2  Design of a single C4D structure: a excitation and pick-up electrodes; b the equivalent circuit electrode The electrodes are layout as a co-planar capacitive sensor This proposed structure and measurement setup can detect two-phase flow channel for both case of conductive liquid and non-conductive liquid 2 Designs and simulations 2.1 Block diagram design of a DC4D for fluidic sensing Figure  shows a block diagram design of the DC4D fluidic sensor based on three electrodes for detecting particles inside both conductive and non-conductive liquid channel This structure consists of two single C4D with an applied carrier sinusoidal signal to the center electrode as the excitation electrode The differential signal between the top and bottom electrodes is then amplified and demodulated Microsyst Technol for removing the carrier components The output signal indicates the different response between two single C4D structures This proposed sensor could detect a particle like plastic particle, air bubble, metal particle and so on inside channel when it passes the electrodes L2 L1 L3 Fluidic pipe d1 d2 L3 d3 2.2 C4D structure (a) Figure  2a shows design of a single C4D fluidic sensor, which consists of two electrodes A sinusoidal signal is applied to left electrode as the excitation electrode and the sensing is the right one Both electrodes sandwich the fluidic channel, which produces two wall capacitors through dielectric layer of shell of channel (Cw1, Cw2) A simplified electrical equivalent circuit of a single C4D structure is shown in Fig. 2b The resistance of conductivity liquid inside channel is RS The wall capacitances Cw1, Cw2 depend on the thickness and permittivity of the dielectric layer and the size of the electrode These two electrodes also make a stray capacitance C0 parallel to the main passageway along the fluidic channel The parasitic effect of the stray capacitance is sometimes eliminated by taking the grounded shield (Kuban and Hauser 2004a, b, 2008; Gas et al 2002) or placing a shield foil between the electrodes (Gas et al 2002; Brito-Neto et al 2005) The analytical form of the cell impedance, Z, defined by the familiar general equation: Z = R1 + jXC = RS Cw2 ω2 − j ω(Cw + C0 ) + RS2 Cw2 C0 ω3 RS C0 Cw ω2 + [ω(Cw + C0 )]2 (1) where R1 and XC are the real and imaginary component of the impedance of C4D, RS is the solution √ resistance, ω = 2πf , f is the measuring frequency, and j = −1 is the imaginary unit, respectively When an alternating actuator voltage is applied to a C D, the detection current is proportional to the magnitude of its admittance, |Y |, which is expressed as: |Y | = R12 + XC2 = (C0 + Cw )2 ω2 G2S + C02 Cw2 ω4 G2S G2S + Cw2 ω2 (2) where GS = 1/RS is the solution conductance It can be seen that in the case of high conductivity solution, GS ≫ Cw ω, the Eq. (2) can be simplified as: |Y | = (R12 + XC2 ) Copper Electrode ≈ (C0 + Cw )ω (3) GS can be ignored in this case Therefore, Eq. (3) shows that the |Y | value mainly depends on the value of wall v C0 Output signal Cw Rs C0 Cw1 Cw1 Rs Cw Output signal R0 R0 (b) Fig.  3  a The DC4D based on three-electrode configuration; b the equivalent circuit and stray capacitance at a specific frequency In order to increase the sensitivity of the measurement, the value of solution resistance RS and wall capacitance Cw1, Cw2 have to be at the same level in correlation with each other This can be done by increasing RS or decreasing ZCw However, in high conductivity solution, RS cannot be increased and GS cannot be decreased Hence, the ZCw must be decreased by making the distance between two electrodes become longer, or increasing the Cw by increasing the length of electrodes 2.3 DC4D based on three‑electrode configuration for fluidic sensor In this paper, a DC4D consists of three electrodes is presented In this design, there are two pick up electrodes, which are outside electrodes The center electrode is excited electrode (see Fig. 3) The differential signal between the two pick up electrodes indicates changing inside the fluidic channel The distance between two electrodes is L2 to make a socalled co-planar capacitor at this point L1 and L3 is length and height of electrode, respectively The U-shape structure held tightly the fluidic channel along the sensor This proposed U-shape is convenient in order to setup and can be used for various size of fluidic channel A pipe with outlet diameter d1 is laid inside three electrodes as shown in Fig. 3a Figure 3b shows the equivalent diagram of the sensor There is a stray capacitance C0 between two electrodes This DC4D structure reduces the effect of common noise inside the fluidic channel and amplifies the differential signal between the two single C4D 13 Fig. 4  Simulated electrical field profile when a plastic particle inside the fresh water channel Microsyst Technol Fig. 5  Simulated electrical field profile when a tin particle inside oil channel (a) DC4D for non-conductive fluidic channel 13 Plastic particle in fresh water Tin particle in oil Air bubble in oil 0.06 0.04 DeltaC - pF For the non-conductivity or low-conductivity liquid (σ  ≤ 0.01 S/m), the resistance of the solution inside the channel is high Therefore, the dominated factor in this case is capacitance component In this work, DC4D sensor is modeled and simulated using Ansoft Maxwell software Oil and fresh water are investigated fluid In the simulated model, copper and plastic is electrode and pipe material, respectively Plastic and tin particle is the investigated object inside the fluidic channel System is assumed working in air ambience Figure  shows three individual planes of the electrostatic field profile when a plastic particle appears at the middle of the two electrodes in fresh water of fluidic channel It can be seen that the distribution of the electric field is non-uniform from inside to outside of the U-shape, even inside the plastic particle because plastic is not conductive material The red areas present the higher electric field magnitude and the blue areas present the lower magnitude In the case of a conductive object such as tin particle moves in oil channel, the electrical field profile is shown in Fig. 5 The electric field distributes mainly along U-shape electrode There is no electrical field inside the conductive particle (blue color inside the particle—see Fig. 5) Figure  shows the simulated capacitance between excitation and pick up electrode change of a single C4D structure when a particle moves though the sensor The capacitance changes up to 80 fF when a 4.18 μl plastic particle moves in fresh water channel as a conductive fluidic Beside conductive fluidic, this work also simulates the capacitance change in non-conductive fluidic when a metal particle and an air bubble passes the electrodes Figure 6 also shows capacitance change of 20 and fF for tin particle and air bubble inside oil channel, respectively 0.08 0.02 -0.02 -0.04 -0.06 -0.08 -0.1 -5 10 15 20 Particle position - mm 25 30 Fig. 6  Capacitance change versus particle position inside a single C4D Figure  shows the simulation of a single C4D capacitance change versus volume of a tin particle inside oil channel It shows that the relation is linear The capacitance changes up to 33.25 fF when tin volume gets value of about 6.61 μl (b) DC4D for conductive fluidic channel When the conductivity of the solution inside the channel is high enough (σ > 0.1 S/m), the influence of capacitance inside the U-shape among electrodes in the total impedance is small, the capacitance in the equivalent equation is mainly depended on the stray capacitance between each single C4D electrode pair C0 (see Fig. 8) However, C0 is unchanged parameter, therefore, the main sensing factor is conductivity of liquid due to cross-section of the fluidic flow change when particle moving Equivalent circuit Microsyst Technol 2.3 30 Admittance - S DeltaC - fF 20 15 10 2.1 1.9 Particle Volume - µl Fig. 7  Single C4D capacitance change versus volume of tin particle in oil channel C0 R1 Cw C3 C2 C1 R2 R3 Electrode Rs Particle l1 Solution l3 l2 L Fig. 8  The equivalent circuit of the DC4D for conductive fluidic channel The circuit diagram of the suggested structure C1 1.8 σ = 0.1 σ = 0.2 σ = 0.3 σ = 0.6 σ = 0.9 0.002 S/m S/m S/m S/m S/m 0.004 0.006 0.008 Particle position (mm) R1 R2 C3 R3 C0 Rs Cw Output Signal R0 0.01 0.012 Fig. 10  The single C4D admittance change when a particle moves though electrode inside conductivity solution The first section (l1) and third section (l3) contain only salt solution The second section (l2) contains salt solution with an immerged plastic particle The wall capacitor can be also divided into three components of C1, C2, and C3, as shown in Fig. 8 The wall capacitance of Cw ≈ 16.939 pF and stray capacitance C0 ≈ 1.995 pF is extracted from the simulated result using Ansoft Maxwell when there is no particle inside the channel The solution and total impedance of the DC4D fluidic sensor is given by: Zsolution = R3 + Rs − C2 AC -5 2.2 25 x 10 i Cw w + A B (4) A = i − w[C2 R2 + C1 (R1 + R2 )] − iC1 C2 R1 R2 w2 B = −w(C1 + C2 + C3 ) − iw2 [C1 R1 (C2 + C3 ) +(C1 + C2 )C3 R2 ] + C1 C2 C3 R1 R2 w3 Fig. 9  The equivalent circuit of the DC4D fluidic sensor Ztotal = of this configuration is shown in the Fig. 9 In this work, plastic particles flows inside different concentration NaCl solutions are investigated The capacitance Cw must be concerned about the wall which is contributed by the shell of the pipe Rs is the resistance of the solution between two electrodes (see Fig. 8) The investigated particle is assumed as the sphere with diameter of l2 L is length of the electrodes When particle inside the U-shape the channel can be divided into three sections corresponded to the l1, l2, and l3 areas (see Fig. 8) Zsolution ZC0 + R0 Zsolution + ZC0 (5) where component of resistances and capacitances are calculated as: l3 l2 l1 ; R3 = ; R2 = ; 2 σsol πR σsol πR − l2 σsol πR2 L l1 l2 l2 Rs = ; C1 = Cw ; C2 = Cw ; C2 = Cw σsol πR L L L R1 = Figure 10 shows admittance change of a single C4D when a plastic particle moves through electrode inside salt solution with several concentrations The admittance |Y | = 1/|Ztotal | 13 Microsyst Technol Table 1  Geometry parameters of the proposed DC4D structure Value (mm) Pipe outlet diameter (d1) Pipe inlet diameter (d2) 3.6 Thickness of the pipe (d3) 0.2 Electrodes width (L1) 12 Distance between two electrode (L2) Electrodes height (L3) 1.52 1.515 Output voltage - V Parameter (a) 1.525 1.51 1.505 1.5 1.495 1.49 1.485 1.48 1.475 0.5 1.5 Time - s (b) Fig. 11  Measurement system setup of the DC4D fluidic sensor decreases non-linearly while the particle moves in between the excitation and the pick up electrode Figure 10 also shows that the admittance of a single C4D increases when the conductivity of liquid σ decreases Output voltage - V 1.6 1.55 1.5 1.45 1.4 3 Fabrication and measurement setups The proposed DC4D is fabricated based on a PCB Electrodes with U-shape are directly bonded on the PCB with built-in differential amplifier and signal processing circuit in order to decrease the parasitic component and common noise The plastic pipe is then laid inside the U-shape electrodes Geometry parameters of the DC4D are listed in the Table 1 Figure 11 shows the measurement setup picture of proposed DC4D fluidic sensor In this work, a sinusoidal signal with 3 V magnitude and 580 kHz frequency is applied to the excitation electrode The two pick-up electrodes voltage is input signal of a differential amplifier, demodulation, and low pass filter circuits The output voltage is then acquired to a computer by using a NI card data acquisition Plastic and tin particles with various sizes is mixed inside fluidic chamber before pumping to the channel for characterized the output response of the sensor when a particle crosses A T-connector, which is configured of two inlets of investigated fluidic and air channel and one outlet, is employed for adding an air bubble inside fluidic channel Volume of the air 13 0.5 1.5 Time - s 2.5 3.5 Fig. 12  The DC4D output voltage when a particle crosses electrodes in machine oil channel: a 4.17 μl air bubble; and b 3.83 μl tin particle bubble can be changed by monitoring the open time of the air inlet and pumping speed of the fluidic syringe 4 Measurement results and discussions 4.1 DC4D for non‑conductive fluidic channel Figure 12 shows output voltage of the sensor when a particle crosses electrodes In this measurement, machine oil as a non-conductive fluidic is used for characterized the proposed DC4D The output is the differential voltage between the two pick up electrodes Therefore, output voltage has a combination of a positive and a negative voltage picks, which indicate that the investigated particle crosses the first and then the second single C4D, respectively Figure 12a Microsyst Technol (a) (a) 1.6 Output Voltage Change - mV 1.4 1.2 ∆ C - fF 0.8 0.6 0.4 0.2 -0.2 300 250 200 150 100 50 -0.4 (b) 0.5 Time - s 1.5 Measured data Linear fitted Volume - µl (b) 20 15 -2 ∆ C - fF ∆ C - fF -1 -3 10 -4 -5 -6 0.5 Time - s 1.5 Fig. 13  The DC4D capacitance change when a particle crosses electrodes in machine oil channel: a 4.17 μl air bubble; and b 3.83 μl tin particle shows output response of a 4.17 μl air bubble crosses the sensor The output voltage changes up to 25 mV Moreover, when a tin particle passes the electrodes the output voltage comes with reverted order of the positive and negative picks compare to the air bubble case thanks to tin particle is metal particle Figure 12b shows output voltage of the sensor for 3.83 μl tin particle Therefore, the order of voltage peak is able to indicate the investigated particle is metal or not Beside detection of a particle inside fluidic channel, this proposed DC4D can be used for measuring flow velocity by dividing the distance between the centers of the two single C4D of (L1  +  L3) by time between the two voltage peaks (see Figs. 3, 12) The capacitance change of DC4D sensor can be extracted from the measurement voltage The capacitances change when a particle crosses electrodes are shown in Fig. 13 Particle Volume - µl Fig. 14  The DC4D output response versus tin particle volume in machine oil channel: a output voltage versus volume; and b capacitance change versus volume 1.7 Output voltage - V -7 Measured data Linear fitted 1.6 1.5 1.4 1.3 Particle in water Particle in NaCl 1.2 Time - s Fig. 15  The DC4D output voltage response when a plastic particle crosses electrodes: a water channel; and b salt solution channel 13 Microsyst Technol Those measured values are almost met the simulated values which are mentioned in Sect. 2.3 The maximum capacitance change is 1.5 and 6.3 fF for 4.17 μl air bubble and 3.83 μl tin particle case, respectively The amplitude of the output voltage and the capacitance change depend on the volume of the investigated particle Figure  14 shows linear relation between output voltage amplitude and capacitance change versus the tin particle volume Therefore, this proposed DC4D sensor allows estimating the size of particle when particle material is known Table 2  The DC4D output voltage amplitude versus particle volume in salt solution and water Plastic particle volume (µl) Output voltage amplitude (mV) Salt solution 0.9 % Fresh water 1.5 4.63 4.88 5.87 6.25 25 115 140 155 180 142 650 700 800 897 9.37 220 1200 4.2 DC4D for conductive fluidic channel 1500 salt solution Linear fitted water Figure  15 shows output voltage of the DC D sensor when a plastic particle cross electrodes in salt solution and water channel as the investigated conductive fluidic The output voltage consists of both negative and positive peaks thank to the differential circuit The output voltage magnitude changes up to 300 mV and 50 mV when a 4.88 μl plastic particle cross electrodes in water channel and plastic particle cross electrode in salt solution channel, respectively Figure  16 shows admittance change of DC4D sensor when a plastic particle crosses water and salt solution The result is approximately matching with the calculated value Table  and Fig. 17 show the relation between output voltage amplitude versus volume of plastic particle in 0.9 % salt solution and water It shows that the relations are linear and output voltage in water channel is about times larger than the 0.9 % salt solution case x 10 Voltage output - mV Admittance change - S Volume - µl 10 Fig. 17  The DC4D output voltage amplitude versus particle volume in salt solution and water Table 3  The DC4D output voltage amplitude versus particle volume in various concentration of salt solution -8 Plastic particle volume (µl) -2 -4 Particle in water Particle in NaCl -6 Time - s Fig. 16  The DC4D admittance change when a plastic particle crosses electrodes: a water channel; and b salt solution channel 13 500 -8 1000 Output voltage amplitude (mV) 0.75 (%) 0.9 (%) 1.5 (%) (%) 1.5 4.25 4.63 4.88 5.87 6.25 35 130 150 165 180 186 25 110 115 140 155 180 16 68 75 76 95 117 10 36 37 45 47 60 9.37 288 220 152 78 The proposed DC4D sensor is also characterized in various concentration of salt solution Table 3 and Fig. 18 shows the relation between output voltage amplitude and investigated plastic particle volume in salt solution It shows that the sensitivity of the sensor reduces when salt concentration in solution is increased The conductivity Microsyst Technol A 300 salt solution 0.75% salt solution 0.9% salt solution 1.5% salt solution 3% Linear fitted 200 14 mm 1.8 B 1.7 150 Output voltage - V Delta V - mV 250 B 100 50 0 Particle volume - µl 1.6 1.5 1.4 1.3 10 1.2 Fig. 18  The DC4D output voltage amplitude versus particle volume in various concentration of salt solution A 0.5 1.45 (s) 1.5 Time - s 2.02 (s) 2.5 3.5 Fig. 20  Velocity of investigated particle inside fluidic channel calculation DeltaV - mV 250 to the A and B point, which are center of each single C4D structure, respectively Therefore, particle velocity can be extracted from distance AB divided by the time between the two voltage picks 200 150 5 Conclusions 100 50 Measured data Linear fitted 0.1 0.2 0.3 0.4 Resistivity - Ω.m 0.5 0.6 Fig. 19  The DC4D output voltage change’s amplitude versus conductive fluidic resistivity of the fluidic can be estimated by using this configuration when volume of the particle is known Figure 19 shows output voltage amplitude change versus conductive fluidic resistivity when a 9.37 µl particle moves through the sensor The relation is linear with sensitivity of about 400 mV/Ω m Therefore, this DC4D sensor can be used for measurement the fluid sensitivity when volume of particle is known In practice, a controlled air bubble pump can be added before sensor inlet for the fluidic sensitivity detector Figure 20 shows output voltage signal and the electrodes layout in this proposed DC4D fluidic sensor for particle velocity detection The two voltage picks are corresponded This paper presents a design, fabrication, and characterized of a DC4D fluidic sensor The sensor is fabricated based on a PCB where the electrodes are directly connected to the differential amplifier and signal processing circuit in order to reduce the parasitic component and common noise The proposed DC4D sensor can be used for both conductive and non-conductive fluidic channel 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 The measured results indicated the linear relation between output voltage and volume of the particle Beside particle detection, this sensor allows measuring velocity of the particle inside fluidic channel thanks to distance and travel time between the two single C4D structure This DC4D fluidic sensor can be used for two-phase flow detection in petroleum industry, particle in fluidic channel detection and living cell in micro vessel detection and counting for biomedical applications Acknowledgments  This research is funded by 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Z, Li Y, Xu Z, Zhu X, Kang Q, Shen D (2013) Determination of equivalent circuit paramerters of a contactless conductive detector in capillary electrophoresis by an imperdance analysis method Electrochem Sci 8:3357–3370 ... component and common noise The proposed DC4D sensor can be used for both conductive and non -conductive fluidic channel Air bubbles and tin particles are pumped through electrodes for characterizing non -conductive. .. 4.1 DC4D for non conductive fluidic channel Figure 12 shows output voltage of the sensor when a particle crosses electrodes In this measurement, machine oil as a non -conductive fluidic is used for. .. setup can detect two-phase flow channel for both case of conductive liquid and non -conductive liquid 2 Designs and simulations 2.1 Block diagram design of a DC4D for fluidic sensing Figure  shows