Shen-Kan Hsiung

Titanium Nitride Membrane Application to Extended Gate Field Effect Transistor pH Sensor Using VLSI Technology

A new process for the fabrication of the extended gate field effect transistor (EGFET) together with complementary metal oxide semiconductor (CMOS) circuits on the same chip is reported. The sensing membrane of the EGFET is titanium nitride (TiN) conducting material and it is fabricated using the r.f. sputtering method. The chips are fabricated using the standard submicron 0.5 µm double poly double metal (DPDM) N-well CMOS IC process. No extra mask is used in the post-process. An instrument amplifier circuit is described that provides an output voltage dependent on the threshold-voltage variations in the sensing membrane. According to the experimental results, the high linear sensitivity approaches 57 mV/pH. The hysteresis voltage is 0.5 mV per cycle of buffer solutions of pH7→pH4→pH7→pH10→pH7. This structure is also insensitive to light. This EGFET is fabricated using the standard technology and no difficulty is experienced in realizing this multi species device. The EGFET and readout circuits are produced using VLSI technology, achieving reduced area and low cost. This device has the advantages of mass production.

All Solid-State Potentiometric Biosensors for Creatinine Determination Based on pH and Ammonium Electrodes

This work investigates a disposable creatinine potentiometric biosensor based on a pH-sensitive electrode and an ammonium ion-selective electrode. An enzyme, creatinine iminohydrolase (CIH) was immobilized directly onto the surface of the electrodes by the entrapment method. According to the experimental results, the creatinine biosensors based on the pH-sensitive electrode and ammonium ion-selective electrode show a rapid response time (t95 < 30 s) and a linear dynamic response range for creatinine determination between 40 muM and 140 muM. Furthermore, the ammonium ion-selective electrode-based biosensors exhibited good operational stability (over 14 times) and storage stability (over 40 days). By discussing the reproducibility and pH effects of the creatinine biosensors, features of creatinine biosensors based on ammonium ion-selective electrodes are described. Moreover, development of a low-cost, solid-state, disposable potentiometric creatinine biosensor based on pH-sensitive electrodes and ammonium ion-selective electrodes is discussed.

Study on a Multi-Ions Sensing System for Monitoring of Blood Electrolytes With Wireless Home-Care System

This study developed a multi-ions sensing system that includes pH, potassium, sodium, and chloride ion sensors with a wireless home-care system. The pH sensor was based on a tin oxide (SnO )/indium tin oxide (ITO) glass, and the potassium, sodium, and chloride ion sensors were based on the pH sensor with sensing membrane. The tin oxide (SnO) sensing membrane was deposited on indium tin oxide (ITO) substrate using a sputtering system. The sensing membranes of the ion sensors were prepared by mixing poly (vinyl chloride) (PVC), bis (2-ethylhexyl) sebacate (DOS), ionophores, and additives. According to the experimental results, sensitivities of the sensors all were over the value 51 mV/decade. The linear range of pH sensor was between pH2 and pH12, the linear ranges of potassium, sodium, and chloride sensors all were over from 1 mM to 1 M. Therefore, the multi-ions sensing system is suitable for monitoring of blood electrolytes. The correlations of the multi-ion sensors under different test solutions also were discussed. Moreover, this study also investigated sensors module, portable module, Bluetooth module, personal computer (PC) terminal, and portable unit of the wireless home-care system. A graphical measurement interface for data recorded and measurement results displayed was designed by National Instrument Lab-VIEW software. According to the experimental results, the measurement data by the wireless home-care system are near the real values. The wireless home-care system could successfully monitor and transmitted the sensing signals.

Effects of Tin Oxide Sputtered on a Carbon Electrode for Fabricating Glucose Biosensor

Tin oxide (SnO 2 ) thin films are sputtered onto a commercial carbon electrode to develop a SnO 2 electrode. A mediator (ferrocene-carboxylic acid) and an enzyme (glucose oxidase) are coimmobilized by polyvinylalcohol bearing styrylpyridinium groups on the surface of the carbon and SnO 2 electrodes, to fabricate carbon and SnO 2 amperometric glucose biosensors. Following electrode modification, the applied potential is reduced from 452 to 236 mV and the current response increases from 320 to 508 μA cm -2 as the carbon and SnO 2 amperometric glucose biosensors are immersed in 360 mg/dL glucose solution. The detection limit of the carbon amperometric glucose biosensor is 360 mg/dL under an applied potential of 452 mV. Furthermore, when the applied potential is set to 236 mV, the detection limit of the SnO 2 amperometric glucose biosensor reaches 600 mg/dL. No significant interference is observed when the applied potential is set at 236 mV. Furthermore, the glucose concentration determined by the glucose presence in the serum sample agrees closely with that in the buffer solution. The merits of reducing the applied potential and increasing current response enable a highly accurate SnO 2 amperometric glucose biosensor based on a low-cost substrate to be developed in this study.

Study on All-Solid-State Chloride Sensor Based on Tin Oxide/Indium Tin Oxide Glass

An all-solid-state chloride electrode based on a tin oxide (SnO2)/indium tin oxide (ITO) glass was developed in this study. The sensing membrane of the electrode was prepared by mixing poly(vinyl chloride) (PVC), bis(2-ethylhexyl) sebacate (DOS), [4,5-dimethy-l-3,6-bis(dodecyloxy)-1,2-phenylene] bis(mercury chloride) (ETH9033), and tridodecylmethyl ammonium chloride (TDDMACl). The mixed solution was mixed with tetrahydrofuran (THF), and then dropped on the sensing window of SnO2/ITO glass. According to the experimental results, the optimal weight ratio were PVC:DOS:ETH9033:TDDMACl=33:66:2:5. At this optimum weight ratio, the sensitivity was 54 mV/dec while the range of linear concentrations of NaCl solutions was between 10-4 and 1 M. The lower detection limit of the sensor reached 8×10-5 M and the response time was less than 1 s. The selectivity coefficient was consistent with the theory of Hofmeister lipophilicity. The lifetime was over 60 days and the repeatability was over 50 times. Moreover, the chloride ion sensor was successfully applied to detecting chloride ions in rinsing solutions for contact lenses, and the experimental results revealed that the correlation coefficient was 0.99.

STUDY ON THE POTENTIOMETRIC GLUCOSE BIOSENSOR BASED ON THE SnO2/ITO/PET

A potentiometric glucose biosensor based on a SnO2/ITO/PET substrate is presented in this study. The sensing membrane of SnO2 is coated on ITO/PET substrate by utilized radio frequency (RF)-sputtering method of semiconductor fabrication. The potentiometric glucose biosensor is established on an FET-type pH sensor. Therein, the glucose oxidase (GOD) and chitosan/multi-wall carbon nano-tubes (chitosan/MWCNTs) are immobilized by 3-glycidoxypropyl trimethoxysilane (3-GPTS). Finally, the drift characteristic and calibration curve of the potentiometric pH sensor and potentiometric glucose biosensor is discussed in the following article. We find the nonideal effect of device reduced significantly, due to the coating of SnO2 thin film.

New Calibration Methods to Eliminate the Non-Ideal Effect of Drift and Hysteresis in All-Solid-State Potassium Electrode

The object of this study is to develop a non-ideal effects calibration method combining of hardware and software, and apply this calibration methods to an all-solid-state potassium electrode. In the hardware method, the calibration circuit owning drift and hysteresis calibration functions are developed to improve the accuracy of the measurement system. The experimental results show that both drift and hysteresis of all-solid-state potassium electrode can be reduced by a calibration circuit. In the software method, a three-time-constant model is used to simulate drift behaviors, and the drift of the all-solid-state potassium electrode is reduced by the software method. The measurement conditions of drift and hysteresis are set as below; the drift time is last for 12 h, the hysteresis loop is 10-3 M → 10-1 M → 10-3 M → 10-5 M → 10-3 M KCl solutions, and the total loop time of hysteresis measurement is 5 min. Simulation of drift behaviors are in 10-2 M and 10-5 M KCl solutions. In addition, the alternated current (AC) impedance analyzer is used to measure the transfer impedance of the sensing membrane. The experimental results obtained by the AC impedance analyzer are used to explain the relationship between the hysteresis and transfer impedance of the sensing membrane.

Study on a pCO2 Sensor Based on a SnO2/Carbon Electrode

This study developed a potentiometric pCO 2 sensor to measure dissolved carbon dioxide. The potentiometric pCO 2 sensor was based on a SnO 2 /carbon structure. The pCO 2 sensor based on the SnO 2 /carbon electrode was made by coating the surface of SnO 2 with a silicone rubber film doped with valinomycin and covered with a solid electrolyte membrane inside the gas-permeable membrane. Moreover, the solid electrolyte membrane was separated from a sample by a polysiloxane membrane, which is permeable to CO 2 . The CO 2 molecules diffused through the membrane into the solid electrolyte membrane, and a resulting pH change was detected by the SnO 2 pH-sensitive membrane. According to the experimental results, the sensitivity of the potentiometric pCO 2 sensor was about 26.1 mV/dec in the range of 0.5-30 mM dissolved CO 2 . The pCO 2 sensors based on the SnO 2 /carbon have an easy fabrication process. Moreover, the SnO 2 /carbon structure could be the substrate of a multisensor.

Study on a multi-ion sensing system with wireless homecare system

This study developed a multi-ion sensing system includes pH, potassium, sodium, and chloride ion sensors with a wireless home-care system. The pH sensor was based on a SnO2/ITO glass, and the potassium, sodium, and chloride ion sensors were based on the pH sensor with sensing membrane. Moreover, the wireless home-care system includes sensors module, portable module, Bluetooth module, personal computer (PC) terminal, and portable unit. According to the experimental results, the wireless system could successfully monitor and transmit the sensing signals.

STUDY ON TIME-CONSTANT MODELS OF SnO2pH SENSOR

The aim of this study was to discuss the hysteresis effect of SnO2 pH sensor based on separative extended gate field effect transistor (SEGFET). Based on the theorem of three time-constants model, hysteresis model is linked with drift effect. Function relationship of pH value and time constant is also derived from the drift effects with difference pH value. Besides, electrochemical impedance spectroscopy (EIS) is utilized to interpret the mechanism of hysteresis effect. Experiments of EIS are carried out in different pH buffer solutions. An equivalent model of sensing membrane is obtained by theorem of EIS. The experimental results indicate that the equivalent circuit elements, such as membrane capacitance and membrane resistance, change with pH. This phenomenon is compared with other literatures and discussed on hysteresis effect.