Development of a low-hysteresis and high-linearity extended gate field-effect transistor-based chloride ion-sensitive microsensor

Abstract

A low-hysteresis voltage and high-sensing linearity chloride ionsensitive sensor based on an extended gate field-effect transistor (EGFET) for real-time water quality monitoring microsystem applications is presented. All of the EGFET-manufacturing processes adopted in this work are compatible with standard integrated circuits planar technology, and therefore, they are very suitable for the mass production. Two EGFETbased chloride ion-sensitive microsensors having same channel width/ length ratio (1000 μm∕10 μm) but with different channel geometries (rectangular and annular types) are presented. At pCl 3 (log½Cl − ¼ −3) test point, a very small hysteresis voltage of the rectangular-and annularchannels EGFET-based Cl − microsensors (5 and 7 mV, respectively) can be achieved. As the concentrations tested ranging from pCl 1 (log½Cl − ¼ −1) to pCl 5 (log½Cl − ¼ −5), a very high-sensing linearity (99.23% and 99.08%) of the two types of EGFET-based Cl − microsensors is achieved. However, the sensitivity of the rectangular-channel EGFETbased Cl − microsensor (45 mV∕pCl) is much higher than that of the annular-channel EGFET-based Cl − microsensor (37 mV∕pCl). The selectivity coefficient of the investigated EGFET-chloride ion sensor under four different interfering ions (OH − , F − , SO 2− 4 , and Br − ) are also measured and analyzed.

A Study on Selectivity and Temperature Coefficients of the Chloride Ion Sensors With RuOx Thin Film

“…Many researchers used PVC, DOS, ETH9033, TDDMACl and THF to prepare chloride ion sensing devices [11], [12], [14]- [17]. They used different weight ratios to prepare chloride ion sensor, and the chloride ion sensing mixtures were mixed and dropped the sensing windows of sensing devices.…”

“…(1) between the sensing film and the solution. The sensing film conditions are related to the quantity of total activates association constant and mobility of all ions in the sensing film [11]. The adsorption amounts of the chloride ion affected the response voltage variations and response time.…”

“…The voltage-time measurement system was also utilized to measure the response voltages for the chloride ion selectivity. However, some researchers [11], [12], [18] investigated the ClO − 4 ion and ClO − ion to affect their chloride ion sensing devices. Our research group [14] put the chloride ion sensing device in the sodium hypochlorite (NaClO) solution.…”

“…The sensitivity comparisons of the different chloride ion sensing devices [11]- [14] were shown in table 1. The poly (vinyl chloride) (PVC) powders, bis (2-ethylhexyl) sebacate (DOS) powders, ionophore {µ-[4,5-dimethyl-3,6-bis (dodecyloxy)-1,2-phenylene]} bis(mercury chloride) (ETH9033) powders, tridodecylmethy-lammonium chloride (TDDMACl) powder and tetrahydrofuran (THF) solution were used to prepare the chloride sensitive solution [11], [12], [14]. They dropped the chloride sensitive solution onto the sensing windows.…”

“…E is the electromotive force (EMF), E0 is the original voltage, α is the chloride ion activity, R is the gas constant (8.316 mole −1 deg −1 ), F is the Faraday coefficient (96487 coulomb). [11]. The chloride ions passed across the helmoltz double layer (HDL) and entered the chloride ion sensing film.…”