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13 pages, 3440 KiB

Open AccessArticle

A New Calibration Circuit Design to Reduce Drift Effect of RuO₂ Urea Biosensors

by Po-Yu Kuo and Zhe-Xin Dong

Sensors 2019, 19(20), 4558; https://doi.org/10.3390/s19204558 - 20 Oct 2019

Cited by 9 | Viewed by 3743

Abstract

The goal of this study was to reduce the drift effect of RuO₂ urea biosensors. A new calibration circuit (NCC) based on the voltage regulation technique with the advantage of having a simple structure was presented. To keep its simplicity, the proposed [...] Read more.

The goal of this study was to reduce the drift effect of RuO₂ urea biosensors. A new calibration circuit (NCC) based on the voltage regulation technique with the advantage of having a simple structure was presented. To keep its simplicity, the proposed NCC was composed of a non-inverting amplifier and a voltage calibrating circuit. A ruthenium oxide (RuO₂) urea biosensor was fabricated to test the calibrating characteristics of the drift rate of the proposed NCC. The experiment performed in this study was divided into two main stages. For the first stage, a sound RuO₂ urea biosensor testing environment was set-up. The RuO₂ urea sensing film was immersed in the urea solution for 12 h and the response voltage was measured using the voltage-time (V–T) measurement system and the proposed NCC. The results of the first stage showed that the RuO₂ urea biosensor has an average sensitivity of 1.860 mV/(mg/dL) and has a linearity of 0.999 which means that the RuO₂ urea biosensor had been well fabricated. The second stage of the experiment verified the proposed NCC’s functions, and the results indicated that the proposed NCC reduced the drift rate of RuO₂ urea biosensor to 0.02 mV/hr (98.77% reduction). Full article

(This article belongs to the Special Issue Potentiometric Bio/Chemical Sensing)

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10 pages, 2641 KiB

Open AccessArticle

Solvent Treatment of Wet-Spun PEDOT: PSS Fibers for Fiber-Based Wearable pH Sensing

by Daniel O. Reid, Rachel E. Smith, Jose Garcia-Torres, John F. Watts and Carol Crean

Sensors 2019, 19(19), 4213; https://doi.org/10.3390/s19194213 - 28 Sep 2019

Cited by 23 | Viewed by 4178

Abstract

There is a growing desire for wearable sensors in health applications. Fibers are inherently flexible and as such can be used as the electrodes of flexible sensors. Fiber-based electrodes are an ideal format to allow incorporation into fabrics and clothing and for use [...] Read more.

There is a growing desire for wearable sensors in health applications. Fibers are inherently flexible and as such can be used as the electrodes of flexible sensors. Fiber-based electrodes are an ideal format to allow incorporation into fabrics and clothing and for use in wearable devices. Electrically conducting fibers were produced from a dispersion of poly (3,4-ethylenedioxythiophene)-poly (styrenesulfonate) (PEDOT: PSS). Fibers were wet spun from two PEDOT: PSS sources, in three fiber diameters. The effect of three different chemical treatments on the fibers were investigated and compared. Short 5 min treatment times with dimethyl sulfoxide (DMSO) on 20 μm fibers produced from Clevios PH1000 were found to produce the best overall treatment. Up to a six-fold increase in electrical conductivity was achieved, reaching 800 S cm⁻¹, with no loss of mechanical strength (150 MPa). With a pH-sensitive polyaniline coating, these fibers displayed a Nernstian response across a pH range of 3.0 to 7.0, which covers the physiologically critical pH range for skin. These results provide opportunities for future wearable, fiber-based sensors including real-time, on-body pH sensing to monitor skin disease. Full article

(This article belongs to the Special Issue Potentiometric Bio/Chemical Sensing)

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10 pages, 1556 KiB

Open AccessArticle

Detection of Cu²⁺ Ions with GGH Peptide Realized with Si-Nanoribbon ISFET

by Olena Synhaivska, Yves Mermoud, Masoud Baghernejad, Israel Alshanski, Mattan Hurevich, Shlomo Yitzchaik, Mathias Wipf and Michel Calame

Sensors 2019, 19(18), 4022; https://doi.org/10.3390/s19184022 - 18 Sep 2019

Cited by 25 | Viewed by 5409

Abstract

The presence of heavy metal ions such as copper in the human body at certain concentrations and specific conditions can lead to the development of different diseases. The currently available analytical detection methods remain expensive, time-consuming, and often require sample pre-treatment. The development [...] Read more.

The presence of heavy metal ions such as copper in the human body at certain concentrations and specific conditions can lead to the development of different diseases. The currently available analytical detection methods remain expensive, time-consuming, and often require sample pre-treatment. The development of specific and quantitative, easy-in-operation, and cost-effective devices, capable of monitoring the level of Cu²⁺ ions in environmental and physiological media, is necessary. We use silicon nanoribbon (SiNR) ion-sensitive field effect transistor (ISFET) devices modified with a Gly–Gly–His peptide for the detection of copper ions in a large concentration range. The specific binding of copper ions causes a conformational change of the ligand, and a deprotonation of secondary amine groups. By performing differential measurements, we gain a deeper insight into the details of the ion–ligand interaction. We highlight in particular the importance of considering non-specific interactions to explain the sensors’ response. Full article

(This article belongs to the Special Issue Potentiometric Bio/Chemical Sensing)

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9 pages, 1720 KiB

Open AccessArticle

Molecular-Charge-Contact-Based Ion-Sensitive Field-Effect Transistor Sensor in Microfluidic System for Protein Sensing

by Haoyue Yang and Toshiya Sakata

Sensors 2019, 19(15), 3393; https://doi.org/10.3390/s19153393 - 2 Aug 2019

Cited by 15 | Viewed by 3949

Abstract

In this paper, we demonstrate the possibility of direct protein sensing beyond the Debye length limit using a molecular-charge-contact (MCC)-based ion-sensitive field-effect transistor (ISFET) sensor combined with a microfluidic device. Different from the MCC method previously reported, biotin-coated magnetic beads are set on [...] Read more.

In this paper, we demonstrate the possibility of direct protein sensing beyond the Debye length limit using a molecular-charge-contact (MCC)-based ion-sensitive field-effect transistor (ISFET) sensor combined with a microfluidic device. Different from the MCC method previously reported, biotin-coated magnetic beads are set on the gate insulator of an ISFET using a button magnet before the injection of target molecules such as streptavidin. Then, the streptavidin—a biotin interaction, used as a model of antigen—antibody reaction is expected at the magnetic beads/gate insulator nanogap interface, changing the pH at the solution/dielectric interface owing to the weak acidity of streptavidin. In addition, the effect of the pH or ionic strength of the measurement solutions on the electrical signals of the MCC-based ISFET sensor is investigated. Furthermore, bound/free (B/F) molecule separation with a microfluidic device is very important to obtain an actual electrical signal based on the streptavidin–biotin interaction. Platforms based on the MCC method are suitable for exploiting the advantages of ISFETs as pH sensors, that is, direct monitoring systems for antigen–antibody reactions in the field of in vitro diagnostics. Full article

(This article belongs to the Special Issue Potentiometric Bio/Chemical Sensing)

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11 pages, 2553 KiB

Open AccessArticle

The Analysis of the Urea Biosensors Using Different Sensing Matrices via Wireless Measurement System & Microfluidic Measurement System

by Jung-Chuan Chou, Cian-Yi Wu, Si-Hong Lin, Po-Yu Kuo, Chih-Hsien Lai, Yu-Hsun Nien, You-Xiang Wu and Tsu-Yang Lai

Sensors 2019, 19(13), 3004; https://doi.org/10.3390/s19133004 - 8 Jul 2019

Cited by 16 | Viewed by 5431

Abstract

Two types of urea biosensors were integrated with a wireless measurement system and microfluidic measurement system. The two biosensors used were (i) a magnetic beads (MBs)-urease/graphene oxide (GO)/titanium dioxide (TiO₂)-based biosensor and (ii) an MBs-urease/GO/ nickel oxide (NiO)-based biosensor, respectively. The [...] Read more.

Two types of urea biosensors were integrated with a wireless measurement system and microfluidic measurement system. The two biosensors used were (i) a magnetic beads (MBs)-urease/graphene oxide (GO)/titanium dioxide (TiO₂)-based biosensor and (ii) an MBs-urease/GO/ nickel oxide (NiO)-based biosensor, respectively. The wireless measurement system work exhibited the feasibility for the remote detection of urea, but it will require refinement and modification to improve stability and precision. The microchannel fluidic system showed the measurement reliability. The sensing properties of urea biosensors at different flow rates were investigated. From the measurement results, the decay of average sensitivity may be attributed to the induced vortex-induced vibrations (VIV) at the high flow rate. In the aspect of wireless monitoring, the average sensitivity of the urea biosensor based on MBs-urease/GO/NiO was 4.780 mV/(mg/dl) and with the linearity of 0.938. In the aspect of measurement under dynamic conditions, the average sensitivity of the urea biosensor based on MBs-urease/GO/NiO were 5.582 mV/(mg/dl) and with the linearity of 0.959. Both measurements performed NiO was better than TiO₂ according to the comparisons. Full article

(This article belongs to the Special Issue Potentiometric Bio/Chemical Sensing)

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12 pages, 6060 KiB

Open AccessArticle

Fast Procedures for the Electrodeposition of Platinum Nanostructures on Miniaturized Electrodes for Improved Ion Sensing

by Francesca Criscuolo, Irene Taurino, Van Anh Dam, Francky Catthoor, Marcel Zevenbergen, Sandro Carrara and Giovanni De Micheli

Sensors 2019, 19(10), 2260; https://doi.org/10.3390/s19102260 - 16 May 2019

Cited by 10 | Viewed by 4176

Abstract

Nanostructured materials have attracted considerable interest over the last few decades to enhance sensing capabilities thanks to their unique properties and large surface area. In particular, noble metal nanostructures offer several advantages including high stability, non-toxicity and excellent electrochemical behaviour. However, in recent [...] Read more.

Nanostructured materials have attracted considerable interest over the last few decades to enhance sensing capabilities thanks to their unique properties and large surface area. In particular, noble metal nanostructures offer several advantages including high stability, non-toxicity and excellent electrochemical behaviour. However, in recent years the great expansion of point-of-care (POC) and wearable systems and the attempt to perform measurements in tiny spaces have also risen the need of increasing sensors miniaturization. Fast constant potential electrodeposition techniques have been proven to be an efficient way to obtain conformal platinum and gold nanostructured layers on macro-electrodes. However, this technique is not effective on micro-electrodes. In this paper, we investigate an alternative one-step deposition technique of platinum nanoflowers on micro-electrodes by linear sweep voltammetry (LSV). The effective deposition of platinum nanoflowers with similar properties to the ones deposited on macro-electrodes is confirmed by morphological analysis and by the similar roughness factor (~200) and capacitance (~18

μ

F/mm

^{2}

). The electrochemical behaviour of the nanostructured layer is then tested in an solid-contact (SC)

L i^{+}

-selective micro-electrode and compared to the case of macro-electrodes. The sensor offers Nernstian calibration with same response time (~15 s) and a one-order of magnitude smaller limit of detection (LOD) (

2.6 \times 10^{- 6}

) with respect to the macro-ion-selective sensors (ISE). Finally, sensor reversibility and stability in both wet and dry conditions is proven. Full article

(This article belongs to the Special Issue Potentiometric Bio/Chemical Sensing)

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15 pages, 2039 KiB

Open AccessArticle

Instant Mercury Ion Detection in Industrial Waste Water with a Microchip Using Extended Gate Field-Effect Transistors and a Portable Device

by Revathi Sukesan, Yi-Ting Chen, Suman Shahim, Shin-Li Wang, Indu Sarangadharan and Yu-Lin Wang

Sensors 2019, 19(9), 2209; https://doi.org/10.3390/s19092209 - 13 May 2019

Cited by 13 | Viewed by 5789

Abstract

Mercury ion selective membrane (Hg-ISM) coated extended gate Field Effect transistors (ISM-FET) were used to manifest a novel methodology for ion-selective sensors based on FET’s, creating ultra-high sensitivity (−36 mV/log [Hg²⁺]) and outweighing ideal Nernst sensitivity limit (−29.58 mV/log [Hg²⁺ [...] Read more.

Mercury ion selective membrane (Hg-ISM) coated extended gate Field Effect transistors (ISM-FET) were used to manifest a novel methodology for ion-selective sensors based on FET’s, creating ultra-high sensitivity (−36 mV/log [Hg²⁺]) and outweighing ideal Nernst sensitivity limit (−29.58 mV/log [Hg²⁺]) for mercury ion. This highly enhanced sensitivity compared with the ion-selective electrode (ISE) (10⁻⁷ M) has reduced the limit of detection (10⁻¹³ M) of Hg²⁺ concentration’s magnitude to considerable orders irrespective of the pH of the test solution. Systematical investigation was carried out by modulating sensor design and bias voltage, revealing that higher sensitivity and a lower detection limit can be attained in an adequately stronger electric field. Our sensor has a limit of detection of 10⁻¹³ M which is two orders lower than Inductively Coupled Plasma Mass Spectrometry (ICP-MS), having a limit of detection of 10⁻¹¹ M. The sensitivity and detection limit do not have axiomatic changes under the presence of high concentrations of interfering ions. The technology offers economic and consumer friendly water quality monitoring options intended for homes, offices and industries. Full article

(This article belongs to the Special Issue Potentiometric Bio/Chemical Sensing)

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9 pages, 2611 KiB

Open AccessEditor’s ChoiceArticle

Sperm-Cultured Gate Ion-Sensitive Field-Effect Transistor for Non-Optical and Live Monitoring of Sperm Capacitation

by Akiko Saito and Toshiya Sakata

Sensors 2019, 19(8), 1784; https://doi.org/10.3390/s19081784 - 14 Apr 2019

Cited by 12 | Viewed by 3698

Abstract

We have successfully monitored the effect of progesterone and Ca²⁺ on artificially induced sperm capacitation in a real-time, noninvasive and label-free manner using an ion-sensitive field-effect transistor (ISFET) sensor. The sperm activity can be electrically detected as a change in pH generated [...] Read more.

We have successfully monitored the effect of progesterone and Ca²⁺ on artificially induced sperm capacitation in a real-time, noninvasive and label-free manner using an ion-sensitive field-effect transistor (ISFET) sensor. The sperm activity can be electrically detected as a change in pH generated by sperm respiration based on the principle of the ISFET sensor. Upon adding mouse sperm to the gate of the ISFET sensor in the culture medium with progesterone, the pH decreases with an increasing concentration of progesterone from 1 to 40 μM. This is because progesterone induces Ca²⁺ influx into spermatozoa and triggers multiple Ca²⁺-dependent physiological responses, which subsequently activates sperm respiration. Moreover, this pH response of the ISFET sensor is not observed for a Ca²⁺-free medium even when progesterone is introduced, which means that Ca²⁺ influx is necessary for sperm activation that results in sperm capacitation. Thus, a platform based on the ISFET sensor system can provide a simple method of evaluating artificially induced sperm capacitation in the field of male infertility treatment. Full article

(This article belongs to the Special Issue Potentiometric Bio/Chemical Sensing)

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Review

Jump to: Research

32 pages, 5591 KiB

Open AccessReview

Recent Advances in Electric-Double-Layer Transistors for Bio-Chemical Sensing Applications

by Ning Liu, Ru Chen and Qing Wan

Sensors 2019, 19(15), 3425; https://doi.org/10.3390/s19153425 - 5 Aug 2019

Cited by 48 | Viewed by 16252

Abstract

As promising biochemical sensors, ion-sensitive field-effect transistors (ISFETs) are used widely in the growing field of biochemical sensing applications. Recently, a new type of field-effect transistor gated by ionic electrolytes has attracted intense attention due to the extremely strong electric-double-layer (EDL) gating effect. [...] Read more.

As promising biochemical sensors, ion-sensitive field-effect transistors (ISFETs) are used widely in the growing field of biochemical sensing applications. Recently, a new type of field-effect transistor gated by ionic electrolytes has attracted intense attention due to the extremely strong electric-double-layer (EDL) gating effect. In such devices, the carrier density of the semiconductor channel can be effectively modulated by an ion-induced EDL capacitance at the semiconductor/electrolyte interface. With advantages of large specific capacitance, low operating voltage and sensitive interfacial properties, various EDL-based transistor (EDLT) devices have been developed for ultrasensitive portable sensing applications. In this article, we will review the recent progress of EDLT-based biochemical sensors. Starting with a brief introduction of the concepts of EDL capacitance and EDLT, we describe the material compositions and the working principle of EDLT devices. Moreover, the biochemical sensing performances of several important EDLTs are discussed in detail, including organic-based EDLTs, oxide-based EDLTs, nanomaterial-based EDLTs and neuromorphic EDLTs. Finally, the main challenges and development prospects of EDLT-based biochemical sensors are listed. Full article

(This article belongs to the Special Issue Potentiometric Bio/Chemical Sensing)

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