A Miniaturized pH Sensor With an Embedded Counter Electrode and a Readout Circuit
TL;DR: In this paper, a silicon-based EISCAP sensor bonded to a glass wafer with an embedded electrode is discussed, and three noble metal electrodes (Pt, Au, Ag) are studied for the ease of integration and performance and it is found that chloridized Ag electrodes exhibit the highest pH sensitivity and the lowest electrode potential drift with time.
Abstract: Electrolyte insulator semiconductor capacitors (EISCAPs) show a shift in the measured capacitance-voltage (C-V) characteristics with changes in the pH of the electrolyte and has the potential to be used as biosensors. The choice of an electrode to the EISCAP is important for reliable measurements. Here, we discuss a silicon-based EISCAP sensor bonded to a glass wafer with an embedded electrode. Three noble metal electrodes (Pt, Au, Ag) are studied for the ease of integration and performance and it is found that the chloridized Ag electrodes exhibit the highest pH sensitivity and the lowest electrode potential drift with time. A readout system that measures the pH of the electrolyte under test is developed and implemented in a programmable system on chip. Calibration of the EISCAP to account for sensor process variations is also incorporated. The pH measurement data on the miniaturized EISCAPs is presented.
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TL;DR: In this article, the authors have reviewed the recent development of R.F. magnetron sputtered thin films for pH sensing applications and showed that these thin film pH sensors offer many advantages, such as ease of packaging, low cost through the use of standard microfabrication processes, miniaturisation, capability of measuring pH at high temperatures, ruggedness and disposability.
Abstract: pH sensors are widely used in chemical and biological applications. Metal oxides-based pH sensors have many attractive features including insolubility, stability, mechanical strength, electrocatalyst and manufacturing technology. Various metal oxide thin films prepared by radio frequency (R.F.) magnetron sputtering have attractive features, including high pH sensitivity, fast response, high resolution, good stability and reversibility as well as potential for measuring pH under conditions that are not favourable for the commonly used glass electrodes-based pH sensors. In addition, thin film pH sensors prepared by R.F. magnetron sputtering offer many advantages, such as ease of packaging, low cost through the use of standard microfabrication processes, miniaturisation, capability of measuring pH at high temperatures, ruggedness and disposability. In this paper, recent development of R.F. magnetron sputtered thin films for pH sensing applications are reviewed.
91 citations
Cites methods from "A Miniaturized pH Sensor With an Em..."
...pH sensors have been developed using a variety of deposition techniques including magnetron sputtering [20–22], sol-gel [17,29], screen-printing [24,30] and plasma enhanced chemical vapour deposition (PECVD) [31,32] and electroplating [33–35]....
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...In recent years, a number of metal oxides based pH sensors have been developed incorporating IrO2 [16–19], RuO2 [20–24], PtO2 [25], SnO2 [25], TaO2 [25], TiO2 [25,26] and Ta2O5 [27,28]. pH sensors have been developed using a variety of deposition techniques including magnetron sputtering [20–22], sol-gel [17,29], screen-printing [24,30] and plasma enhanced chemical vapour deposition (PECVD) [31,32] and electroplating [33–35]....
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TL;DR: In this article, a 3-aminopropyl triethoxysilane (APTES) linker was used to enhance the sensitivity of EIS devices with textured dielectric surface.
Abstract: The possible mechanisms governing the enhancement of sensitivities of Electrolyte-insulator-semiconductor (EIS) devices upon surface modification (texturing) realized by electrostatic attachment of silica particles using 3-aminopropyl triethoxysilane (APTES) as a linker are presented. EIS devices were fabricated with a textured dielectric surface using SiO2 particles (of diameters 475, 135, and 70 nm) and screen printed Ag/AgCl electrodes. A maximum pH sensitivity of 52.4 mV/pH was achieved for the EIS device textured with 70 nm particle size while the sensitivity with the planar dielectric was 37.1 mV/pH. The APTES modification enhanced the adsorption of H + ions by protonation of the ‐NH2 to ‐NH3 + sites as seen from the capacitance versus voltage (C-V) hysteresis voltages. UV-Vis absorption and photoluminescence (PL) spectra indicated that the surface defects on the textured surface increased with decreasing particle size. Zeta potential measurements suggested a combined acid-base behavior of textured surface with the formation of ‐NH3 + and −Si-O − groups. Theflatband voltage study showed that surface textured with 70 nm SiO2 particles provided the optimum ratio of Si-OH and ‐NH2 groups. The various chemical treatments during texturization did not affect the
16 citations
TL;DR: In this article, the authors have developed a complete triglyceride biochip wherein the enzyme for hydrolysis and the counter electrode for signal transduction are integrated with a miniaturized EISCAP sensor.
Abstract: This paper reports on the design and fabrication of electrolyte insulator semiconductor capacitor (EISCAP) devices to detect triglycerides in the form of microreactors fabricated by bulk micromachining of silicon. We have developed a complete triglyceride biochip wherein the enzyme for hydrolysis and the counter electrode for signal transduction are integrated with a miniaturised EISCAP sensor. A compact readout system that measures the triglyceride concentration in blood serum under test has been developed and is implemented in a Programmable System on Chip (PSoC®). The miniaturised EISCAP devices are tested using blood serum samples to estimate the triglyceride concentration within the clinical range of 50 to 150 mg dL−1 and the time taken by the readout system to calibrate the sensor and to measure the triglyceride is less than 5 minutes.
13 citations
TL;DR: In this article, an electrolyte-insulator-semiconductor (EIS) device with an improved sensitivity brought about by texturization of the functionalized dielectric at the Dielectric/electrolyte interface by electrostatic attachment of nanoparticle and mesoparticle was presented.
Abstract: We report the fabrication of an electrolyte–insulator–semiconductor (EIS) device with an improved sensitivity brought about by texturization of the functionalized dielectric at the dielectric/electrolyte interface by electrostatic attachment of nanoparticle and mesoparticle. Improvement in sensitivities up to 42% over the nontextured (control) devices was obtained with SiO2 particles on SiO2 dielectric. The sensitivity was a function of the size of the particles with higher sensitivities being obtained with smaller particle sizes. The possible contributions of the chemical modification of the dielectric surface by the aminosilanes resulting in the modification of the surface charge, and of the physical modifications by particle texturization leading likely to enhancement of the surface densities of the active binding sites, were highlighted. A novel design for the EIS reservoir for possible improved circuit integration and manufacturability, involving a two-step reservoir in photoresist was demonstrated. This device was capable of characterizing sample volumes as small as $20~\mu $ L. A $2 \times 1$ and a $2 \times 2$ array was also demonstrated, which could be utilized for multianalyte detection.
11 citations
Cites methods from "A Miniaturized pH Sensor With an Em..."
...materials have an effect on these parameters [37], and the effect of different reference electrode materials in the form compatible with the device design used here is the subject of a future work....
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TL;DR: A monolithic pH measurement system with a power conditioning system for supply power derived from harvested energy and the test results of the prototype circuit closely match the measurement results obtained by its commercial counterpart.
Abstract: This paper presents a monolithic pH measurement system with a power conditioning system for supply power derived from harvested energy. The proposed system includes a low-power highly linear pH readout circuits with wide pH values (0–14) and a power conditioning unit based on low dropout (LDO) regulator. The readout circuit provides a square-wave output with the frequency being highly linear corresponding to the input pH values. To achieve that, a simple operational transconductance amplifier is employed to linearly convert the pH sensor output voltage to a current. To overcome the process variations, a simple calibration method is employed in the design which makes the output frequency stay constant over the process, supply voltage, and temperature variations. The prototype circuit is designed and fabricated in a standard 0.13- $\mu \text{m}$ CMOS process and demonstrates a good linearity to cover the entire pH value range from 0 to 14, while the voltage regulator provides a stable supply voltage 1.25 V for the system. The proposed sensor consumes $12.8~\mu \text{W}$ of power for a typical pH value of 7 while occupying a die area of 0.017 mm2. The total die area including the readout circuit and the LDO is 160 $\mu \text{m}\,\,\times 110\,\,\mu \text{m}$ , which makes this system a suitable candidate for low-power miniaturized sensor systems. Both electrical test and in vitro measurement are performed, and a commercial pH meter is employed to make a performance comparison with this paper. The test results of the prototype circuit closely match the measurement results obtained by its commercial counterpart.
5 citations
Cites background from "A Miniaturized pH Sensor With an Em..."
...recently published works, such as ISFET [8]–[10], optical fibers [11], [12], capacitance measurement [13], [14], coil-type...
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References
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TL;DR: A DNA sequencing technology in which scalable, low-cost semiconductor manufacturing techniques are used to make an integrated circuit able to directly perform non-optical DNA sequencing of genomes, showing its robustness and scalability by producing ion chips with up to 10 times as many sensors and sequencing a human genome.
Abstract: The seminal importance of DNA sequencing to the life sciences, biotechnology and medicine has driven the search for more scalable and lower-cost solutions. Here we describe a DNA sequencing technology in which scalable, low-cost semiconductor manufacturing techniques are used to make an integrated circuit able to directly perform non-optical DNA sequencing of genomes. Sequence data are obtained by directly sensing the ions produced by template-directed DNA polymerase synthesis using all-natural nucleotides on this massively parallel semiconductor-sensing device or ion chip. The ion chip contains ion-sensitive, field-effect transistor-based sensors in perfect register with 1.2 million wells, which provide confinement and allow parallel, simultaneous detection of independent sequencing reactions. Use of the most widely used technology for constructing integrated circuits, the complementary metal-oxide semiconductor (CMOS) process, allows for low-cost, large-scale production and scaling of the device to higher densities and larger array sizes. We show the performance of the system by sequencing three bacterial genomes, its robustness and scalability by producing ion chips with up to 10 times as many sensors and sequencing a human genome.
2,246 citations
"A Miniaturized pH Sensor With an Em..." refers background in this paper
...Ion Sensitive Field Effect Transistors (ISFET) can also be used to measure changes in pH [8], [9] and recently improvement in the pH sensitivity of ISFETs using layers of ZrO2, InN and Tantalum oxide have been reported [10]–[12]....
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Book•
18 Mar 1982
TL;DR: In this article, the authors present a method for extracting interface trap properties from the conductance of a metal oxide Silicon Capacitor at intermediate and high frequency intervals, and demonstrate that these properties can be used for charge trapping in the oxide.
Abstract: Introduction. Field Effect. Metal Oxide Silicon Capacitor at Low Frequencies. Metal Oxide Silicon Capacitor at Intermediate and High Frequencies. Extraction of Interface Trap Properties from the Conductance. Interfacial Nonuniformities. Experimental Evidence for Interface Trap Properties. Extraction of Interface Trap Properties from the Capacitance. Measurement of Silicon Properties. Charges, Barrier Heights, and Flatband Voltage. Charge Trapping in the Oxide. Instrumentation for Measuring Capacitor Characteristics. Oxidation of Silicon--Oxidation Kinetics. Oxidation of Silicon--Technology. Control of Oxide Charges. Models of the Interface. Appendices. Subject Index. Symbol Index.
2,101 citations
01 Jan 1982
TL;DR: In this article, the authors present a method for extracting interface trap properties from the conductance of a metal oxide Silicon Capacitor at intermediate and high frequency intervals, and demonstrate that these properties can be used for charge trapping in the oxide.
Abstract: Introduction. Field Effect. Metal Oxide Silicon Capacitor at Low Frequencies. Metal Oxide Silicon Capacitor at Intermediate and High Frequencies. Extraction of Interface Trap Properties from the Conductance. Interfacial Nonuniformities. Experimental Evidence for Interface Trap Properties. Extraction of Interface Trap Properties from the Capacitance. Measurement of Silicon Properties. Charges, Barrier Heights, and Flatband Voltage. Charge Trapping in the Oxide. Instrumentation for Measuring Capacitor Characteristics. Oxidation of Silicon--Oxidation Kinetics. Oxidation of Silicon--Technology. Control of Oxide Charges. Models of the Interface. Appendices. Subject Index. Symbol Index.
1,855 citations
TL;DR: The development of an ion-sensitive solid-state device that combines the principles of an MOS transistor and a glass electrode and can be used for measurements of ion activities in electrochemical and biological environments is described.
Abstract: The development of an ion-sensitive solid-state device is described. The device combines the principles of an MOS transistor and a glass electrode and can be used for measurements of ion activities in electrochemical and biological environments. Some preliminary results are given.
1,841 citations
"A Miniaturized pH Sensor With an Em..." refers background in this paper
...ELECTROLYTE Insulator Semiconductor Capacitors (EISCAPs) are sensitive to changes in the pH of the electrolyte [1], [2], and can be used for detecting bio-analytes like triglycerides and urea through enzymatic reactions that cause a change in the pH of the electrolyte [3]....
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TL;DR: A new solid-state device has been developed that makes it possible to measure ion activities without using a reference electrode and has the properties of both a glass electrode and a field-effect transistor.
Abstract: A new solid-state device has been developed for the measurement of ion activities in electrochemical and biological environments. One can recognize in the device the properties of both a glass electrode and a field-effect transistor. This justifies the name ion-sensitive field-effect transistor. The device makes it possible to measure ion activities without using a reference electrode. For its application, a special electronic circuit is described. Results of measured Na + and H + ion activities are given in detail. As an example for electrophysiological application, results are shown of recorded extracellular ion pulses measured with a guinea pig taenia coli.
588 citations
"A Miniaturized pH Sensor With an Em..." refers background in this paper
...ELECTROLYTE Insulator Semiconductor Capacitors (EISCAPs) are sensitive to changes in the pH of the electrolyte [1], [2], and can be used for detecting bio-analytes like triglycerides and urea through enzymatic reactions that cause a change in the pH of the electrolyte [3]....
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