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The ion-sensitive field-effect transistor (ISFET) is a popular technology utilized for pH sensing applications. In this work, we have presented the fabrication, characterization, and electrochemical modeling of an aluminum oxide (Al2O3)-gate ISFET-based pH sensor. The sensor is fabricated using well-established metal-oxide-semiconductor (MOS) unit processes with five steps of photolithography, and the sensing film is patterned using the lift-off process. The Al2O3 sensing film is deposited over the gate area using pulsed-DC magnetron-assisted reactive sputtering technique in order to improve the sensor performance. The material characterization of sensing film has been done using x-ray diffraction, field-emission scanning electron microscopy, energy-dispersive spectroscopy, and x-ray photoelectron spectroscopy techniques. The sensor has been packaged using thick-film technology and encapsulated by a dam-and-fill approach. The packaged device has been tested in various pH buffer solutions, and a sensitivity of nearly 42.1 mV/pH has been achieved. A simulation program with integrated circuit emphasis (SPICE) macromodel of the Al2O3-gate ISFET is empirically derived from the experimental results, and the extracted electrochemical parameters have been reported. The drift and hysteresis characteristics of the Al2O3-gate ISFET were also studied, and the obtained drift rates for different pH buffer solutions of 4, 7, and 10 are 0.136 µA/min, 0.124 µA/min, and 0.108 µA/min, respectively. A hysteresis of nearly 5.806 µA has been obtained. The developed sensor has high sensitivity along with low drift and hysteresis.
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INTRODUCTION: Celiac disease (CD) has been linked to portal hypertension (PHT) of varied etiology, but the causality association has never been proved. We aim to study the prevalence of CD in patients of PHT of different etiology. METHODS: A prospective observational study was conducted from June 2017 to December 2018 involving all the cases of PHT of varied etiology. Consecutive patients of PHT with chronic liver disease (CLD) of defined etiology like ethanol, viral hepatitis (B or C), Budd-Chiari syndrome (BCS), autoimmune-related cirrhosis, and cryptogenic CLD (cCLD) (group A) and those with noncirrhotic PHT (NCPHT), which included noncirrhotic portal fibrosis (NCPF) and extrahepatic portal vein obstruction (EHPVO) (group B), were screened for CD by IgA anti-tTG antibody followed by duodenal biopsy in serology-positive patients. RESULTS: Out of a total of 464 patients, group A constituted 382 patients, CLD related to ethanol (155), cCLD (147), hepatitis B (42), hepatitis C (21), autoimmune (10), and BCS (7), whereas 82 patients were in group B with NCPF (64) and EHPVO (18). Total 29 patients were diagnosed with CD in both groups, 17 in group A (4.5%) and 12 in group B (14.6%). In group A, 13 patients with cCLD, two with HBV-related CLD, one with BCS, and one with autoimmune-related CLD were concomitantly diagnosed as CD. In group B, CD was diagnosed in 12 patients of NCPF (11) and EHPVO (1). Liver histology showed chronic hepatitis in two patients and was normal in three patients. CONCLUSION: CD is common in PHT of different etiology, especially in cCLD, NCPH and autoimmune hepatitis; however, the etiological basis for this association is still to be defined. The likelihood of CD is higher in liver disease than the general population, and these patients should be screened for CD.
