DOCSLIB.ORG

40 Years of ISFET Technology: from Neuronal Sensing to DNA Sequencing

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
40 Years of ISFET Technology: from Neuronal Sensing to DNA Sequencing An interview with the ISFET inventor Professor Piet Bergveld, by Chris Toumazou and Piet Bergveld Pantelis Georgiou 40 years of ISFET technology: From neuronal sensing to DNA sequencing apparatus as part of my collection of classic we followed were still concerning tubes!). I medical equipment at the University [of Twente]. remember that at a certain moment I thought After World War Two the physicians there to myself: Well, then you can also make a pill, also started operations to take away part of or a with an oscillator and a sensor that changes complete lung, and I remember my father an FM signal with pH and pressure for talking about a patient that had died instance, which can then be remotely received unexpectedly after an operation. In fact nobody using an FM receiver. So, in 1963 I developed knew beforehand who could withstand such an a telemetric lab-in-a-pill, based on a operation and who could not. And I remember transistorised Hartley oscillator in the group that they therefore decided to build next to the of Measurement Technology, to measure existing mechanical and electrical workshops, pressure and temperature in the intestines where I spent much of my free time, of patients. The ultimate goal was to also a new workshop for making biomedical measure pH, but on studying pH glass measurement instruments. These instruments electrodes I discovered that they were not yet were made to measure, in the laboratory, patient small enough to be incorporated into my pill. blood parameters such as CO2, oxygen and pH. Nevertheless, this was my fi rst acquaintance With these they could then decide whether a with pH electrodes. certain patient could be operated on or not. I think that that experience, at the age of about The invention of the ISFET after 10–12 years, inspired me and made me decide the creation of the MOSFET that developing new measurement equipment for medical applications would be my profession in Q: What was the fi rst idea concerning the the future. ISFET? A: From 1964-65, I did my Master’s degree at An early vision: invention of Philips in Eindhoven at the Natlab in the group a lab-in-a-pill of the late Dr. Klein, who became Professor later on at the Technical University of Delft. Q: Did you study biomedical engineering at a At that time they were developing ECG, This article presents a personal account of the ABOVE: Professor Piet Bergveld university? EMG and EEG amplifi ers, still based on life and scientifi c journey of Professor Piet holding one of the very fi rst A: When the time came to go to university in the application of vacuum tubes, and they had Bergveld, the inventor and founding father of the ISFET wafers 1960, I decided I was keener on electrical started to look at using transistors, with BOTTOM RIGHT: One of the Ion-Sensitive Field Effect Transistor (ISFET). fi rst 1 inch wafers as produced engineering than medicine. I felt I had enough junction fi eld effect transistors in the fi rst stage, The interview gives a unique overview of how by the technician Arie Kooi, experience from the mechanical, electrical and because of their high input impedance. It ISFET technology has evolved over the years, containing 6 ISFETs. The source instrumental workshops from the sanatorium, was my task to develop a differential amplifi er and drain connections are at and the challenges faced during the development the side of one single ISFET, to and that it would be better for the patient that I that made use of the high impedance transistors from its initial use in neuronal sensing to the be able to mount them on the be an engineer rather than a medic. That was for differential measurements, but solving in technology we see today, which has huge small end of a Perspex holder, the reason why I studied electrical engineering the meantime the problem of their bad with connections at the side. potential in the current era of genetic at the University of Eindhoven. This output resistance. I did this by technology. university was founded two years applying cascades of JFETs and before I enrolled as a new bipolar transistors and reached Introduction to the biomedical fi eld technical university in the in this way rejection ratios Netherlands, although there of the order of 10,000 for Q: How did you get into the biomedical fi eld? was no biomedical a differential amplifi er. This A: I was already involved in this area because as engineering, which I preferred. was the subject of my Master’s a child I lived from 1948–1960 with my family at But I got a good education with thesis. the TBC health-resort Sanatorium Beatrixoord, a fair engineering approach and I It was also the time that in the southern part of the province Friesland. My always did my practical work on a Philips had developed their father was the economic director, so we lived in medical subject which I thought out very fi rst MOSFETs, which I heard the campus of the hospital which was in the forest myself, and I looked for a group which was about because I worked in the Natlab. But as the TB patients were, before World War Two, willing to accept this for the credit points. in those early days you could hardly fi nd two treated only with clean air. At that time the only This was at the time that AM radio was MOSFETs with the same set of properties, thing that they could measure was taking Röntgen replaced by FM and transistors also came into so it was not yet useful for the new images of the lungs. I still have the old Röntgen existence (although the courses in electronics differential amplifi ers. ❯❯ doi: 10.1049/el.2011.3231 Electronics Letters Dec. 2011 – Special Supplement: Semiconductors in Personalised Medicine S7 But then, having had experience with reactions on glass for sensing pH from my lab-in-a-pill work at the university, I proposed to Dr Klein that we could potentially use the silicon oxide of these MOSFETs directly as a glass membrane, similar to the pH probe. This was when I came up with the idea for creating an ISFET. Dr Klein’s response was: “We at Philips do our utmost to encapsulate chips as well as possible against moisture and you want to put it directly in contact with the liquid? Forget about it.’’ To which I replied “Well, you should never say something like that to somebody from Friesland, because then you are sure that he will do it anyway.” [laughs] It is clear that at that time this initial idea for using the silicon oxide layer of a MOSFET as a sensing layer was not well received, and was not pursued by Philips. Many years later I discovered that somebody from Philips Natlab had written a small piece on my idea in an obscure German journal called Neues aus der Technik; done to prevent someone, including myself, from patenting it. Waiting for a fi eld to emerge; ABOVE: A photo of an Initially I created the amplifi ers and the fi rst extended gate FET experimental set-up with an colleagues created the signal processing Parkinson’s disease, but also necessary for ISFET placed on the fl exor tibialis of a locusta instrumentation, in addition to my fi rst physical executing my ISFET plans. Q: How did you proceed? ABOVE RIGHT: Cover of sensor, which was a tremor sensor, fi rst based on A: I then moved to work at the University Bergveld’s doctorate thesis a microphone and later on so-called pixie Creation of the fi rst ISFET which shows how axons and of Twente, in Enschede. This third technical microelectronics may meet beams. for neuronal sensing university of the Netherlands was founded in each other in the future For the measurement of the electrical 1961, and started lecturing in 1963, so I was one BELOW: One of the ISFETs brain activity we used very long glass Q: How did you develop the fi rst ISFETs? mounted on a Perspex holder, of its fi rst academics. to be able to place it on a nerve needles with a 50 micron-thick platinum wire A: Some years later, in 1967, the late Prof. O.W. I was still highly interested in biomedical or muscle passing through the tip, which I then had to make Memelink from Philips was appointed at our engineering but, of course, it did not yet exist in into a shielded cable to connect to the amplifi er. department to start a chair on Solid State those days. My fi rst boss, Prof. Ir. M.P. The problem was, however, you could not Electronics. He decided to found a clean room Breedveld, however, was interested in starting it measure fairly steep action potentials due to the facility focused on the fabrication of MOSFETs. up in the future, and this was why I chose capacitance of the line. With my knowledge from I was his fi rst client; I said: “I can use your Twente. Nevertheless, in the fi rst years the my Master’s degree at Philips, I realised you MOSFETs. Bring them here, but don’t bring the courses that I had to give were pure electrical, could fi x this problem using a fi eld effect gate metal,” as I wanted to try out sensing ions mechanical and chemical engineering. But in the transistor, built in the tip of the electrode as a remotely in the brain based on my original evenings I studied physiology, biology and single chip, with the 50 micron wire directly ISFET concept.
Load more

Recommended publications
  • The Design, Fabrication, and Testing of Corrugated Silicon Nitride Diaphragms
    36 JOURNAL OF MICROELECTROMECHANICAL SYSTEMS, VOL. 3, NO. I, MARCH 1994 The Design, Fabrication, and Testing of Corrugated Silicon Nitride Diaphragms Patrick R. Scheeper, Wouter Olthuis, and Piet Bergveld Abstract-Silicon nitride corrugated diaphragms of 2 mm x 2 mm x lpm have been fabricated with 8 circular corrugations, having depths of 410, or 14 pm. The diaphragms with 4-pm-deep corrugations show a measured mechanical sensitivity (increase in the deflection over the increase in the applied pressure) which is 25 times larger than the mechanical sensitivity of flat diaphragms I of equal size and thickness. Since this gain in sensitivity is due to Fig. I. Schematic cross-sectional view of a circular corrugated diaphragm reduction of the initial stress, the sensitivity can only increase in and characteristic parameters. the case of diaphragms with initial stress. A simple analytical model has been proposed that takes the influence of initial tensile stress into account. The model predicts to-run reproducibility is determined by the reproducibility of that the presence of corrugations increases the sensitivity of the the initial conditions of the reactor (affected by contamination, diaphragms, because the initial diaphragm stress is reduced. The adsorbed water, previously deposited layers) and the accuracy model also predicts that for corrugations with a larger depth the sensitivity decreases, because the bending stiffness of the of the instruments which control the reactor temperature, the corrugations then becomes dominant. These predictions have pressure and the mass flow of the process gases. Variations of been confirmed by experiments. a factor 2 of the initial stress have been measured.
    [Show full text]
  • Development of a Hydrogel-Based Carbon Dioxide Sensor
    DEVELOPMENT OF A HYDROGEL-BASED CARBON DIOXIDE SENSOR A TOOL FOR DIAGNOSING GASTROINTESTINAL ISCHEMIA The described research has been carried out at the “Miniaturized Systems For Biomedical And Environmental Applications” group (BIOS) of the MESA+ Research Institute at the University of Twente, Enschede, the Netherlands. The research was financially supported by the Dutch Technology Foundation, STW, project TTF.5439. Samenstelling promotiecommissie: Voorzitter prof. dr. ir. J. van Amerongen Universiteit Twente Promotor prof. dr. ir. P. Bergveld Universiteit Twente Co-promotor prof. dr. ir. A. van den Berg Universiteit Twente Assistent promotor dr. ir. W. Olthuis Universiteit Twente Leden prof. dr. J.F.J. Engbersen Universiteit Twente prof. dr.-ing. habil G. Gerlach Technische Universität Dresden dr. J.J. Kolkman Medisch Spectrum Twente prof. P.F. Gibson Royal Academy of Engineering Title: DEVELOPMENT OF A HYDROGEL-BASED CARBON DIOXIDE SENSOR - a tool for diagnosing gastrointestinal ischemia Cover: Front-side: artist impression of the hydrogel-based carbon dioxide sensor. Back-side: some relevant pictures and scientific notations collected during the research Author: Sebastiaan Herber ISBN: 90-365-2144-0 Printing: Febodruk B.V. Enschede Copyright © 2005 by Sebastiaan Herber, Enschede, the Netherlands DEVELOPMENT OF A HYDROGEL-BASED CARBON DIOXIDE SENSOR A TOOL FOR DIAGNOSING GASTROINTESTINAL ISCHEMIA PROEFSCHRIFT ter verkrijging van de graad van doctor aan de Universiteit Twente, op gezag van rector magnificus, prof. dr. W.H.M. Zijm, volgens besluit van het College voor Promoties in het openbaar te verdedigen op vrijdag 13 mei 2005 om 13:15 uur door Sebastiaan Herber geboren op 1 februari 1979 te Utrecht Dit proefschrift is goedgekeurd door promotor: prof.
    [Show full text]
  • Monolayer Mos2 and Wse2 Double Gate Field Effect Transistor As Super Nernst Ph Sensor and Nanobiosensor
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Elsevier - Publisher Connector Sensing and Bio-Sensing Research 11 (2016) 45–51 Contents lists available at ScienceDirect Sensing and Bio-Sensing Research journal homepage: www.elsevier.com/locate/sbsr Monolayer MoS2 and WSe2 Double Gate Field Effect Transistor as Super Nernst pH sensor and Nanobiosensor Abir Shadman ⁎, Ehsanur Rahman, Quazi D.M. Khosru Department of Electrical and Electronic Engineering, Bangladesh University of Engineering and Technology, Dhaka 1000, Bangladesh article info abstract Article history: Two-dimensional layered material is touted as a replacement of current Si technology because of its ultra-thin Received 27 June 2016 body and high mobility. Prominent transition metal dichalcogenides (TMD), Molybdenum disulphide (MoS2), Received in revised form 24 August 2016 as a channel material for Field Effect Transistor has been used for sensing nano-biomolecules. Tungsten Accepted 26 August 2016 diselenide (WSe2), widely used as channel for logic applications, has also shown better performance than other 2D materials in many cases. pH sensor is integrated with Nanobiosensor most often since charges (value and type) of many biomolecules depend on pH of the solution. Ion Sensitive Field Effect Transistor with Silicon Keywords: – fi Double gate FET and III V materials has been traditionally used for pH sensing. Experimental result for MoS2 eld effect transistor 2D material as pH sensor has been reported in recent literature. However, no simulation-based study has been done for single pH sensor layer TMD FET as pH sensor or bio sensor. In this paper, novel MoS2 and WSe2 monolayer double gate FETs are Nernst limit proposed for pH sensor operation in Super Nernst regime and protein detection.
    [Show full text]
  • Avalanche ISFET Sensing Chip for DNA Sequencing Mohammad Uzzal
    University of New Mexico UNM Digital Repository Electrical and Computer Engineering ETDs Engineering ETDs 7-1-2016 Avalanche ISFET Sensing Chip for DNA Sequencing Mohammad Uzzal Follow this and additional works at: https://digitalrepository.unm.edu/ece_etds Part of the Electrical and Computer Engineering Commons Recommended Citation Uzzal, Mohammad. "Avalanche ISFET Sensing Chip for DNA Sequencing." (2016). https://digitalrepository.unm.edu/ece_etds/263 This Dissertation is brought to you for free and open access by the Engineering ETDs at UNM Digital Repository. It has been accepted for inclusion in Electrical and Computer Engineering ETDs by an authorized administrator of UNM Digital Repository. For more information, please contact [email protected]. Mohammad Mohiuddin Uzzal Candidate Electrical and Computer Engineering Department This dissertation is approved, and it is acceptable in quality and form for publication: Approved by the Dissertation Committee: Dr. Payman Zarkesh-Ha , Chairperson Dr. Vince Calhoun Dr. Jeremy S. Edwards Dr. Ashwani K. Sharma Dr. Paul Szauter Avalanche ISFET Sensing Chip for DNA Sequencing By Mohammad Mohiuddin Uzzal B.Sc. in EEE, Bangladesh Uni. of Engg. and Tech. (BUET), Bangladesh, 2002 M.S.E in EE, Arizona State University (ASU), AZ, USA, 2006 M.B.A in Finance/Management, IBA, University of Dhaka, Bangladesh, 2008 DISSERTATION Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy Engineering The University of New Mexico Albuquerque, New Mexico July 2016 II @2016, Mohammad Mohiuddin Uzzal III DEDICATION To my family and friends IV ACKNOWLEDGMENT My graduate student life in University of New Mexico was one of the most exciting, joyful and rewarding experience in my life.
    [Show full text]
  • Field-Effect Transistor Based Biosensing of Glucose Using Carbon
    Laboratoire d'Informatique, de Robotique et de Microelectronique´ de Montpellier Summer Internship 2019 Field-effect transistor based biosensing of glucose using carbon nanotubes and monolayer MoS2 Nathan Ullberg supervised by Aida Todri-Sanial examined by Carla Puglia November 24, 2019 Contents Abstract....................................2 Acknowledgements..............................3 1 Introduction..................................4 2 Background..................................5 2.1 Field-effect transistors (FET)....................5 2.1.1 Brief history and overview.................5 2.1.2 Characteristic curves....................6 2.1.3 Transconductance, threshold voltage, and ON/OFF ratio7 2.2 Field-effect biosensing (FEB)....................8 2.3 CNT-FETs.............................. 10 2.3.1 Dry CNT transistors.................... 10 2.3.2 Functionalization for glucose sensing........... 11 2.4 MoS2-FETs.............................. 12 2.4.1 Dry MoS2 transistors.................... 12 2.4.2 Biosensing applications................... 14 2.5 Graphene-FETs............................ 16 3 Results..................................... 17 3.1 CNT devices............................. 17 3.1.1 Fabrication......................... 17 3.1.2 SEM and AFM characterization.............. 19 3.1.3 Electrical characterization................. 22 3.2 MoS2 devices............................. 24 3.2.1 Fabrication......................... 24 3.2.2 Electrical characterization................. 25 4 Conclusions and next steps.........................
    [Show full text]
  • 6 7 Integrated Sensor Array for On-Line Monitoring
    6 7 INTEGRATED SENSOR ARRAY FOR ON‐LINE MONITORING MICRO BIOREACTORS The described research has been carried out at the BIOS Lab‐on‐a‐Chip group of the MESA+ Institute for Nanotechnology of the University of Twente, Enschede, The Netherlands. The research was financially supported by the Dutch Science Foundation (NWO) through the ACTS program IBOS (Integration of Biosynthesis and organic synthesis), DSM Anti‐Infectives, Organon and Applikon. Samenstelling promotiecommissie: voorzitter: prof. dr. W.H.M. Zijm secretaris: prof. dr. ir. A.J. Mouthaan promotor: prof. dr. ir. A. van den Berg assistent promotor: prof. dr. J.G.E. Gardeniers leden: prof. dr. P. Renaud prof. dr. ir. P.H. Veltink prof. dr. I. Vermes dr. H.J. Noorman prof. dr. ir. J.J. Heijnen Title: Integrated sensor array for on‐line monitoring micro bio reactors Author: Erik Krommenhoek ISBN: 978‐90‐365‐2593‐0 Printing: PrintPartners Ipskamp Copyright © 2007 by Erik Krommenhoek, Enschede, The Netherlands 8 9 INTEGRATED SENSOR ARRAY FOR ON‐LINE MONITORING MICRO BIOREACTORS PROEFSCHRIFT ter verkrijging van de graad van doctor aan de Universiteit Twente, op gezag van rector magnificus, Prof. Dr. W.H.M. Zijm, volgens het besluit van het College voor Promoties in het openbaar te verdedigen op donderdag 29 november 2007 om 13.15 uur door Erik Eduard Krommenhoek geboren op 29 juli 1979 te Apeldoorn Dit proefschrift is goedgekeurd door: promotor: prof. dr. ir. Albert van den Berg co‐promotor: prof. dr. Han Gardeniers Contents Contents Chapter 1: Scope and outline of this thesis .................................................................
    [Show full text]
  • Electroactive Gate Materials for a Hydrogen Peroxide Sensitive /Sup E
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Universiteit Twente Repository 26 IEEE SENSORS JOURNAL, VOL. 2, NO. 1, FEBRUARY 2002 Electroactive Gate Materials for a Hydrogen Peroxide i Sensitive MOSFET Dam T. V. Anh, W. Olthuis, and P. Bergveld Abstract—This paper describes the detection principle of a hydrogen peroxide sensor based on the electrolyte metal oxide semiconductor field effect transistor (iMOSFET) and possibilities of using different types of redox materials as the gate material for the sensor with respect to the sensitivity and detection limit. After discussing the fundamentals of hydrogen peroxide detection and a short description of the iMOSFET characteristics in terms of its threshold voltage, the basic measuring principle of hydrogen peroxide using the iMOSFET is shown. The iMOSFET with electro-active gate materials such as iridium oxide, potassium ferric ferrocyanide, and Os polyvinylpyridine containing peroxi- dase, have been studied. These different materials are compared with each other with respect to their sensitivity, detection limit, and stability. The sensitivity of the sensors is improved by applying an external current between the gate and the solution. Index Terms—iMOSFET, hydrogen peroxide sensor, redox material. Fig. 1. Potential-pH equilibrium diagram of the system hydrogen peroxide- I. INTRODUCTION water, at 25 C. HE determination of trace amounts of hydrogen peroxide T is of practical importance in medical, environmental, for assaying hydrogen peroxide, such as chemical and optical and biological fields. It is necessary to determine hydrogen (spectrophotometric, fluorescent, and chemiluminescence) peroxide, not only in chemical and industrial processes (for approaches.
    [Show full text]
  • The ISFET Invention by Professor Emeritus Dr Piet Bergveld
    The ISFET Invention by Professor emeritus Dr Piet Bergveld The origin of the chair BIOS, Lab-on-a-chip group, is in fact the invention of the ISFET, the first chip-based chemical sensor, by Piet Bergveld, since 1965 an employee of the chair Medical Electronics, later on called Bio-informatics. Bergveld’s interest was the development of a tiny ion sensitive sensor for application in neurophysiology, initiated by his work in the Parkinson project of the chair at the time 1965-1970. He first published about the necessary electronic systems for measurements with a remote field effect transistor at the place of the actual measurement: inside the brain or on top of a nerve or muscle. In the case that the field effect transistor (FET) could be a MOSFET, at that time developed by the chair Solid State Electronics, Bergveld decided to leave out the metal (M) of the gate of the device, resulting in the ISFET (Ion Sensitive FET), whereas the gate oxide could directly touch a nerve or muscle. The first publications of this new type of chemical sensor appeared in 1970 and 1972, which formed the basis of Bergveld’s PhD thesis in 1973. After the pioneering period, to proof the operation of various ISFET types, the company Cordis in Roden, the Netherlands, started the commercialisation of the ISFET, in close co- operation with the University of Twente, focussed on a catheter with pH sensor for intracorporeal blood measurements. In addition Bergveld developed a whole series of new sensors based on the ISFET principle, such as an EnzymeFET, an ImmunoFET etc.
    [Show full text]
  • Recent Advances of Field-Effect Transistor Technology for Infectious Diseases
    biosensors Review Recent Advances of Field-Effect Transistor Technology for Infectious Diseases Abbas Panahi 1,2, Deniz Sadighbayan 1,3 , Saghi Forouhi 1,2 and Ebrahim Ghafar-Zadeh 1,2,3,* 1 Biologically Sensors and Actuators (BioSA) Laboratory, Lassonde School of Engineering, York University, Keel Street, Toronto, ON M3J 1P3, Canada; [email protected] (A.P.); [email protected] (D.S.); [email protected] (S.F.) 2 Department of Electrical Engineering and Computer Science, Lassonde School of Engineering, York University, Keel Street, Toronto, ON M3J 1P3, Canada 3 Department of Biology, Faculty of Science, York University, Keel Street, Toronto, ON M3J 1P3, Canada * Correspondence: [email protected]; Tel.: +1-(416)-736-2100 (ext. 44646) Abstract: Field-effect transistor (FET) biosensors have been intensively researched toward label-free biomolecule sensing for different disease screening applications. High sensitivity, incredible miniatur- ization capability, promising extremely low minimum limit of detection (LoD) at the molecular level, integration with complementary metal oxide semiconductor (CMOS) technology and last but not least label-free operation were amongst the predominant motives for highlighting these sensors in the biosensor community. Although there are various diseases targeted by FET sensors for detection, infectious diseases are still the most demanding sector that needs higher precision in detection and integration for the realization of the diagnosis at the point of care (PoC). The COVID-19 pandemic, nevertheless, was an example of the escalated situation in terms of worldwide desperate need for fast, specific and reliable home test PoC devices for the timely screening of huge numbers of people to restrict the disease from further spread.
    [Show full text]
  • MOSFET Dam Thi Van Anh, Wouter Olthuis, and Piet Bergveld
    284 IEEE SENSORS JOURNAL, VOL. 4, NO. 3, JUNE 2004 Work Function Characterization of Electroactive i Materials Using an MOSFET Dam Thi Van Anh, Wouter Olthuis, and Piet Bergveld Abstract—Materials with redox properties have been widely used in sensing applications. Understanding the redox properties of these materials is an important issue. In order to investigate the redox properties, there are several methods, such as using the Kelvin probe and a conductivity sensor, or using other well-known electrochemical techniques. In this paper, we introduce another possibility to characterize redox materials by investigating their work function using an electrolyte metal-oxide semiconductor field effect transistor (iMOSFET) device, in which the studied Fig. 1. Illustration of a change in the work function related to a redox process. redox material is applied as gate electrode. In the iMOSFET, the conductivity of the channel is modulated by the work function of the studied material. The change in the work function of a redox are present in the environment where the measurement is done. material due to electrically and chemically induced processes will Moreover, the conductivity of the material may be changed, i be shown by an example of the MOSFET having a potassium not only by electrochemical or chemical oxidation or reduction, ferric ferrocyanide gate. but also by chemical exchange reactions, such as protonation Index Terms—Electroactive material, electrolyte metal-oxide in aqueous media or gas adsorption in a dry state [3]. Particu- i semiconductor field effect transistor ( MOSFET), work function. larly, when the redox reaction of the material occurs in the gas phase (for example, in the case of gas sensors), a change in con- I.
    [Show full text]
  • Lecture 8 Notes.Pages
    !1 Special Lecture Series Biosensors and Instrumentation Lecture 8 - FET Based Sensors This lecture looks at the Ion Sensitive Field Effect Transistor (ISFET) which is the basic chemical sensor that can be made using the same basic structure as a MOSFET, but with some important changes. The initial implementation of the ISFET was a pH sensor operating in a potentiometric mode and that’s what this lecture presents first. We will then go on to look at different instrumentation methods for the ISFET, some of which are suitable for integration with CMOS processes for single chip microsystems or the creation of sensor arrays. Issues with ISFET measurement will be introduced along with techniques to deal with these with differential instrumentation. In the subsequent lecture we will look at some alternative implementations, for example using weak inversion mode of operation, additional sensing modes, or nano-wire structures. An example of a sensor chip developed at Edinburgh which combines pH, pO2 and amperometric biosensing capabilities will also be covered. Ion Sensitive Electrodes We begin by reviewing the concept of ion selective or ion sensitive electrodes, potentiometric devices where the electrode potential is measured when there’s no current flowing. They are characterised by the the Nernst equation: RT a E = E0 + ln i1 nF a ! ✓ i2 ◆ This depends on the ratio of activities (approximated as concentrations in dilute solutions) of the oxidised (ai1) and reduced species (ai2) being measured. Glass membrane electrodes, which you should be somewhat familiar with are a common form of potentiometric ISE but they’re difficult to miniaturise and so there’s been a lot of activity looking at trying to make a solid state equivalent.
    [Show full text]
  • Thesis Would Not Exist
    Abstract Direct and indirect sensing of biological interactions using pH-sensitive silicon nanoscale field effect transistors Luye Mu 2017 Biosensors are playing an increasingly important role in gathering analytical data across various fields. From personalized monitoring, to food and water safety, to drug discovery, these tools are allowing human discoveries and quality of life to advance at an unprecedented pace. Nano-field-effect-transistors (nanoFET) are highly sensitive sensing elements with a multitude of benefits. They offer ease of integration with on-chip signal conditioning circuitry, and they are low power and low noise devices, which means they can be made portable. The measurement of macromolecular interactions is particularly useful in biosensing, however, the main drawback is that Debye screening in physiological buffers limits the applicability of FET sensors in real world macromolecular sensing applications. We overcome this challenge by translating the specific biorecognition event into a pH response, which, due to the small size of protons, is immune to screening. In this work, we use noise spectroscopy to drive the design of optimal nanoFET sensors, and demonstrate the application of this approach to measure meaningful macromolecular interactions. Using low frequency noise measurements and modelling, we discuss that different applications have different sensor optimizations in terms of sensing dielectric and dimensions. For our application of pH sensing, we demonstrate that Al2O3 is the preferred pH-sensing dielectric based on its higher signal to noise ratio, compared to SiO2. We also briefly discuss scaling effects, and explain the rationale behind preferring larger devices when the trap density is equal. We then use our nanoFETs in biologically-meaningful applications.
    [Show full text]