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12 pages, 1367 KB

Open AccessArticle

Organic ISFET Based on Poly (3-hexylthiophene)

by Giuseppe Scarpa, Anna-Lena Idzko, Anandi Yadav and Stefan Thalhammer

Sensors 2010, 10(3), 2262-2273; https://doi.org/10.3390/s100302262 - 19 Mar 2010

Cited by 34 | Viewed by 11966

Abstract

We have fabricated organic field-effect transistors (OFETs) with regioregular poly(3-hexylthiophene) (P3HT) operable at low-voltages in liquid solutions, suitable for in vitro biosensing applications. Measurements in electrolytes have shown that the performance of the transistors did not deteriorate and they can be directly used [...] Read more.

We have fabricated organic field-effect transistors (OFETs) with regioregular poly(3-hexylthiophene) (P3HT) operable at low-voltages in liquid solutions, suitable for in vitro biosensing applications. Measurements in electrolytes have shown that the performance of the transistors did not deteriorate and they can be directly used as ionsensitive transducers. Furthermore, more complex media have been tested, with the perspective of cell analysis. Degradation effects acting on the device operating in liquid could be partly compensated by adopting an alternate current measuring mode. Full article

(This article belongs to the Special Issue ISFET Sensors)

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12 pages, 230 KB

Open AccessArticle

Study of Sodium Ion Selective Electrodes and Differential Structures with Anodized Indium Tin Oxide

by Jyh-Ling Lin and Hsiang-Yi Hsu

Sensors 2010, 10(3), 1798-1809; https://doi.org/10.3390/s100301798 - 4 Mar 2010

Cited by 28 | Viewed by 14575

Abstract

The objective of this work is the study and characterization of anodized indium tin oxide (anodized-ITO) as a sodium ion selective electrode and differential structures including a sodium-selective-membrane/anodized-ITO as sensor 1, an anodized-ITO membrane as the contrast sensor 2, and an ITO as [...] Read more.

The objective of this work is the study and characterization of anodized indium tin oxide (anodized-ITO) as a sodium ion selective electrode and differential structures including a sodium-selective-membrane/anodized-ITO as sensor 1, an anodized-ITO membrane as the contrast sensor 2, and an ITO as the reference electrode. Anodized-ITO was fabricated by anodic oxidation at room temperature, a low cost and simple manufacture process that makes it easy to control the variation in film resistance. The anodized-ITO based on EGFET structure has good linear pH sensitivity, approximately 54.44 mV/pH from pH 2 to pH 12. The proposed sodium electrodes prepared by PVC-COOH, DOS embedding colloid, and complex Na-TFBD and ionophore B12C4, show good sensitivity at 52.48 mV/decade for 10⁻⁴M to 1 M, and 29.96 mV/decade for 10⁻⁷M to 10⁻⁴M. The sodium sensitivity of the differential sodium-sensing device is 58.65 mV/decade between 10⁻⁴M and 1 M, with a corresponding linearity of 0.998; and 19.17 mV/decade between 10⁻⁵M and 10⁻⁴M. Full article

(This article belongs to the Special Issue ISFET Sensors)

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9 pages, 574 KB

Open AccessArticle

Observation and Measurement of Negative Differential Resistance on PtSi Schottky Junctions on Porous Silicon

by Seyedeh Maryam Banihashemian, Hassan Hajghassem, Alireza Erfanian, Majidreza Aliahmadi, Mansor Mohtashamifar and Seyed Mohamadhosein Mosakazemi

Sensors 2010, 10(2), 1012-1020; https://doi.org/10.3390/s100201012 - 27 Jan 2010

Cited by 12 | Viewed by 10569

Abstract

Nanosize porous Si is made by two step controlled etching of Si. The first etching step is carried on the Si surface and the second is performed after deposition of 75 Å of platinum on the formed surface. A platinum silicide structure with [...] Read more.

Nanosize porous Si is made by two step controlled etching of Si. The first etching step is carried on the Si surface and the second is performed after deposition of 75 Å of platinum on the formed surface. A platinum silicide structure with a size of less than 25 nm is formed on the porous Si surface, as measured with an Atomic Forced Microscope (AFM). Differential resistance curve as a function of voltage in 77 K and 100 K shows a negative differential resistance and indicates the effect of quantum tunneling. In general form, the ratio of maximum to minimum tunneling current (PVR) and the number of peaks in I-V curves reduces by increasing the temperature. However, due to accumulation of carriers behind the potential barrier and superposition of several peaks, it is observed that the PVR increases at 100 K and the maximum PVR at 100 K is 189.6. Full article

(This article belongs to the Special Issue ISFET Sensors)

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7 pages, 464 KB

Open AccessArticle

Low Magnetic Field Detection Using a CuPt Nano Structure Made on a SiO₂/Si Structure

by Hassan Hajghassem, Seyedeh Maryam Banihashemian and Majidreza Aliahmadi

Sensors 2009, 9(12), 9734-9740; https://doi.org/10.3390/s91209734 - 2 Dec 2009

Viewed by 11449

Abstract

A Si/SiO₂/CuPt structure is formed by depositing a very thin SiO₂ layer between CuPt and P-type Si layers using e-beam evaporation. SEM images show the formation of CuPt nano clusters with an average size of less than 100 nm. This [...] Read more.

A Si/SiO₂/CuPt structure is formed by depositing a very thin SiO₂ layer between CuPt and P-type Si layers using e-beam evaporation. SEM images show the formation of CuPt nano clusters with an average size of less than 100 nm. This structure shows high sensitivity to applied magnetic fields at 77K and at low and high dc voltages such that magnetic field as low as 6 mT is detected using I-V and I-B measurements. The variation of current with various magnetic field strength at the constant voltage shows also an oscillatory behavior. The sensitivity of this structure to magnetic fields is believed to be due to small nano size of the platinum–copper structures as well as their discrete energy states and the tunneling of carriers into the insulating layer. Our results indicate that this structure may be a good candidate for small, simple, low cost and sensitive low magnetic field detectors. Full article

(This article belongs to the Special Issue ISFET Sensors)

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13 pages, 440 KB

Open AccessArticle

A CMOS-Compatible, Low-Noise ISFET Based on High Efficiency Ion-Modulated Lateral-Bipolar Conduction

by Sheng-Ren Chang and Hsin Chen

Sensors 2009, 9(10), 8336-8348; https://doi.org/10.3390/s91008336 - 21 Oct 2009

Cited by 17 | Viewed by 15873

Abstract

Ion-sensitive, field-effect transistors (ISFET) have been useful biosensors in many applications. However, the signal-to-noise ratio of the ISFET is limited by its intrinsic, low-frequency noise. This paper presents an ISFET capable of utilizing lateral-bipolar conduction to reduce low-frequency noise. With a particular layout [...] Read more.

Ion-sensitive, field-effect transistors (ISFET) have been useful biosensors in many applications. However, the signal-to-noise ratio of the ISFET is limited by its intrinsic, low-frequency noise. This paper presents an ISFET capable of utilizing lateral-bipolar conduction to reduce low-frequency noise. With a particular layout design, the conduction efficiency is further enhanced. Moreover, the ISFET is compatible with the standard CMOS technology. All materials above the gate-oxide are removed by simple, die-level post-CMOS process, allowing ions to modulate the lateral-bipolar current directly. By varying the gate-to-bulk voltage, the operation mode of the ISFET is controlled effectively, so is the noise performance measured and compared. Finally, the biasing conditions preferable for different low-noise applications are identified. Under the identified biasing condition, the signal-to-noise ratio of the ISFET as a pH sensor is proved to be improved by more than five times. Full article

(This article belongs to the Special Issue ISFET Sensors)

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Review

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37 pages, 889 KB

Open AccessReview

Microfabricated Reference Electrodes and their Biosensing Applications

by M. Waleed Shinwari, David Zhitomirsky, Imran A. Deen, P. R. Selvaganapathy, M. Jamal Deen and D. Landheer

Sensors 2010, 10(3), 1679-1715; https://doi.org/10.3390/s100301679 - 2 Mar 2010

Cited by 282 | Viewed by 35744

Abstract

Over the past two decades, there has been an increasing trend towards miniaturization of both biological and chemical sensors and their integration with miniaturized sample pre-processing and analysis systems. These miniaturized lab-on-chip devices have several functional advantages including low cost, their ability to [...] Read more.

Over the past two decades, there has been an increasing trend towards miniaturization of both biological and chemical sensors and their integration with miniaturized sample pre-processing and analysis systems. These miniaturized lab-on-chip devices have several functional advantages including low cost, their ability to analyze smaller samples, faster analysis time, suitability for automation, and increased reliability and repeatability. Electrical based sensing methods that transduce biological or chemical signals into the electrical domain are a dominant part of the lab-on-chip devices. A vital part of any electrochemical sensing system is the reference electrode, which is a probe that is capable of measuring the potential on the solution side of an electrochemical interface. Research on miniaturization of this crucial component and analysis of the parameters that affect its performance, stability and lifetime, is sparse. In this paper, we present the basic electrochemistry and thermodynamics of these reference electrodes and illustrate the uses of reference electrodes in electrochemical and biological measurements. Different electrochemical systems that are used as reference electrodes will be presented, and an overview of some contemporary advances in electrode miniaturization and their performance will be provided. Full article

(This article belongs to the Special Issue ISFET Sensors)

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23 pages, 388 KB

Open AccessReview

ISFET Based Microsensors for Environmental Monitoring

by Cecilia Jimenez-Jorquera, Jahir Orozco and Antoni Baldi

Sensors 2010, 10(1), 61-83; https://doi.org/10.3390/s100100061 - 24 Dec 2009

Cited by 157 | Viewed by 26924

Abstract

The use of microsensors for in-field monitoring of environmental parameters is gaining interest due to their advantages over conventional sensors. Among them microsensors based on semiconductor technology offer additional advantages such as small size, robustness, low output impedance and rapid response. Besides, the [...] Read more.

The use of microsensors for in-field monitoring of environmental parameters is gaining interest due to their advantages over conventional sensors. Among them microsensors based on semiconductor technology offer additional advantages such as small size, robustness, low output impedance and rapid response. Besides, the technology used allows integration of circuitry and multiple sensors in the same substrate and accordingly they can be implemented in compact probes for particular applications e.g., in situ monitoring and/or on-line measurements. In the field of microsensors for environmental applications, Ion Selective Field Effect Transistors (ISFETs) have a special interest. They are particularly helpful for measuring pH and other ions in small volumes and they can be integrated in compact flow cells for continuous measurements. In this paper the technologies used to fabricate ISFETs and a review of the role of ISFETs in the environmental field are presented. Full article

(This article belongs to the Special Issue ISFET Sensors)

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21 pages, 1308 KB

Open AccessReview

An Integrated ISFET Sensor Array

by Kazuo Nakazato

Sensors 2009, 9(11), 8831-8851; https://doi.org/10.3390/s91108831 - 4 Nov 2009

Cited by 74 | Viewed by 21429

Abstract

A monolithically integrated ISFET sensor array and interface circuit are described. A new high-density, low-power source-drain follower was developed for the sensor array. ISFETs were formed by depositing Au/Ti extended-gate electrodes on standard MOSFETs, then thin silicon nitride layers using catalytic chemical vapor [...] Read more.

A monolithically integrated ISFET sensor array and interface circuit are described. A new high-density, low-power source-drain follower was developed for the sensor array. ISFETs were formed by depositing Au/Ti extended-gate electrodes on standard MOSFETs, then thin silicon nitride layers using catalytic chemical vapor deposition and/or SU-8 protective layers were formed on the extended-gate electrodes. Applications for the array include: (1) pH detection by statistical distribution observing time and space fluctuations; (2) DNA detection using thiol-modified or silane-coupled oligonucleotides; (3) bio-image sensing by converting photons to electrons using Photosystem I of Thermosynechococcus elongatus, and sensing the converted electric charges by ISFETs. Full article

(This article belongs to the Special Issue ISFET Sensors)

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21 pages, 484 KB

Open AccessReview

Ion-Sensitive Field-Effect Transistor for Biological Sensing

by Chang-Soo Lee, Sang Kyu Kim and Moonil Kim

Sensors 2009, 9(9), 7111-7131; https://doi.org/10.3390/s90907111 - 7 Sep 2009

Cited by 392 | Viewed by 35441

Abstract

In recent years there has been great progress in applying FET-type biosensors for highly sensitive biological detection. Among them, the ISFET (ion-sensitive field-effect transistor) is one of the most intriguing approaches in electrical biosensing technology. Here, we review some of the main advances [...] Read more.

In recent years there has been great progress in applying FET-type biosensors for highly sensitive biological detection. Among them, the ISFET (ion-sensitive field-effect transistor) is one of the most intriguing approaches in electrical biosensing technology. Here, we review some of the main advances in this field over the past few years, explore its application prospects, and discuss the main issues, approaches, and challenges, with the aim of stimulating a broader interest in developing ISFET-based biosensors and extending their applications for reliable and sensitive analysis of various biomolecules such as DNA, proteins, enzymes, and cells. Full article

(This article belongs to the Special Issue ISFET Sensors)

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14 pages, 803 KB

Open AccessReview

Photocurable Polymers for Ion Selective Field Effect Transistors. 20 Years of Applications

by Natalia Abramova and Andrei Bratov

Sensors 2009, 9(9), 7097-7110; https://doi.org/10.3390/s90907097 - 7 Sep 2009

Cited by 25 | Viewed by 15777

Abstract

Application of photocurable polymers for encapsulation of ion selective field effect transistors (ISFET) and for membrane formation in chemical sensitive field effect transistors (ChemFET) during the last 20 years is discussed. From a technological point of view these materials are quite interesting because [...] Read more.

Application of photocurable polymers for encapsulation of ion selective field effect transistors (ISFET) and for membrane formation in chemical sensitive field effect transistors (ChemFET) during the last 20 years is discussed. From a technological point of view these materials are quite interesting because they allow the use of standard photo-lithographic processes, which reduces significantly the time required for sensor encapsulation and membrane deposition and the amount of manual work required for this, all items of importance for sensor mass production. Problems associated with the application of this kind of polymers in sensors are analysed and estimation of future trends in this field of research are presented. Full article

(This article belongs to the Special Issue ISFET Sensors)

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