Highly Sensitive and Transparent Urea-EnFET Based Point-of-Care Diagnostic Test Sensor with a Triple-Gate a-IGZO TFT.

Won-Ju Cho,Seong-Kun Cho

doi:10.3390/s21144748

Abstract

In this study, we propose a highly sensitive transparent urea enzymatic field-effect transistor (EnFET) point-of-care (POC) diagnostic test sensor using a triple-gate amorphous indium gallium zinc oxide (a-IGZO) thin-film pH ion-sensitive field-effect transistor (ISFET). The EnFET sensor consists of a urease-immobilized tin-dioxide (SnO2) sensing membrane extended gate (EG) and an a-IGZO thin film transistor (TFT), which acts as the detector and transducer, respectively. To enhance the urea sensitivity, we designed a triple-gate a-IGZO TFT transducer with a top gate (TG) at the top of the channel, a bottom gate (BG) at the bottom of the channel, and a side gate (SG) on the side of the channel. By using capacitive coupling between these gates, an extremely high urea sensitivity of 3632.1 mV/pUrea was accomplished in the range of pUrea 2 to 3.5; this is 50 times greater than the sensitivities observed in prior works. High urea sensitivity and reliability were even obtained in the low pUrea (0.5 to 2) and high pUrea (3.5 to 5) ranges. The proposed urea-EnFET sensor with a triple-gate a-IGZO TFT is therefore expected to be useful for POC diagnostic tests that require high sensitivity and high reliability.

Highlights

Urea sensors are utilized in various fields, such as food [1,2], environmental protection [3,4], pharmaceuticals, fertilizers, and especially bio-clinical analysis [5]
Chronic kidney disease or end-stage renal disease is generally caused by a progressive loss of kidney function; this increases the level of urea in the blood, which is known as azotemia or uremia
A schematic diagram of the fabricated triple-gate amorphous indium gallium zinc oxide (a-IGZO) thin film transistor (TFT) is shown in Figure 2a, and optical microscopy and photographic images of the device are shown in Figures 2b and 2c, respectively

Summary

Introduction

Urea sensors are utilized in various fields, such as food [1,2], environmental protection [3,4], pharmaceuticals, fertilizers, and especially bio-clinical analysis [5]. We implemented the urea-EnFET sensor by electrically connecting triple-gate a-IGZO TFTs and urease-immobilized SnO2 sensing membrane EG.

Results

Conclusion