Highly sensitive FET sensors for cadmium detection in one drop of human serum with a hand-held device and investigation of the sensing mechanism

Abstract

As the heavy metal contamination is becoming worse, monitoring the heavy metal content in water or human body gets more and more important. In this research, a cadmium ion-selective field effect transistor (Cd-ISFET) for rapidly detecting cadmium ions has been developed and the mechanism of the sensor is also investigated in depth. Our Cd-ISFET sensor exhibits high sensitivity beyond the ideal Nernst sensitivity, wide dynamic range, low detection limit (∼10−11M), which is comparable with inductively coupled plasma mass spectrometry, and easy operation enabling people to detect cadmium ion by themselves. From the analysis of electrical measurement results, this Cd-ISFET is preferred to operate at the bias with the maximum transconductance of the FET to enhance the sensor signal. The AC impedance measurement is carried out to directly investigate the mechanism of an ion-selective membrane (ISM). From impedance results, the real part of the total impedance, which is the resistance, was shown to dominate the sensor signal. The potential drop across the ISM is caused by the heavy metal ion in the membrane, which is employed to the gate of the FET via an extended gate electrode. Cadmium ion detection in one drop of human serum with this sensor was demonstrated. This cost-effective and highly sensitive sensor is promising and can be used by anyone and anywhere to prevent people from cadmium poisoning.

An integrated wearable sticker based on extended-gate AlGaN/GaN high electron mobility transistors for real-time cortisol detection in human sweat

“…24–29 Above all, the two-dimensional electron gas (2DEG) in the AlGaN/GaN HEMT sensor is located in close proximity to the surface, rendering it highly responsive to variations in surface potential. In recent years, AlGaN/GaN HEMT sensors have been successfully employed for the detection of proteins (biomarkers, antigens), 30–32 ions, 29,33–36 DNA hybridization, 37 and pH 38–41 in solution or serum samples due to their various advantages mentioned above. However, challenges such as skin compatibility issues, 39 bulky test devices, 42,43 and limited integration with sweat collection and transport systems 44 have consistently hindered these biosensors from evolving into a truly wearable sweat sensing platform.…”

Dual Ion-Selective Membrane Deposited Ion-Sensitive Field-Effect Transistor Integrating a Whole Blood Processing Microchamber for In Situ Blood Ion Testing

“…Another example is using ISFET with an indium tin oxide (ITO) film and a Na ISM to detect the Na + ion level in urine . The last example is using a Cd ISM-deposited ISFET to measure Cd 2+ ions in the serum …”

“…25 The last example is using a Cd ISM-deposited ISFET to measure Cd 2+ ions in the serum. 26 To enable real-time and continuous blood ion sensing, in this study, we proposed a dual ISM-deposited ISFET (DISM− ISFET) sensor integrating a microchamber to perform on-chip serum extraction and in situ Na + /K + ion sensing. To process whole blood samples, we designed a PMMA (polymethyl methacrylate)-made microchamber consisting of the anti-D immunoglobulin-coated trench array and embedded filter membrane to achieve a rapid and high-purity serum extraction from 500 μL of whole blood sample in 3 min.…”