Research in the field of biosensors has enormously increased over the recent years. Since the development of the first biosensor by Clark in 1962, where an amperometric oxygen electrode was immobilised with an enzyme (glucose oxidase),1 many efforts have been invested to create functional hybrid systems. These functional hybrid systems often benefit from the coupling of the unique recognition and signal-amplification abilities of biological systems, that have been developed and optimised during millions of years of evolution, with an artificial man-made signal detection and amplification system. Thus, the combination of knowledge in bioand electrochemistry, solid-state and surface physics, bioengineering, integrated circuit silicon technology and data processing offers the possibility of a new generation of highly specific, sensitive, selective and reliable micro (bio-)chemical sensors and sensor arrays. Moreover, the rapid development of silicon technology has stimulated the fabrication of miniaturised analytical systems such as mTAS (micro total analysis system), ‘lab on chip’ sensors, electronic tongue devices and electronic noses.2–17 Among the variety of proposed concepts and different types of biosensors, the integration of biologically active materials together with an ISFET (ion-selective field-effect transistor) is one of the most attractive approaches. The ISFET was invented by Bergveld18 in 1970 and has been introduced as the first miniaturised silicon-based chemical sensor. In spite of distinct difficulties with regard to practical applications, the great interest in ISFET-based biosensors, so-called biologically modified field-effect transistors (BioFETs), has generated a great number of publications, a flow that shows no sign of diminishing. The reason therefore is that silicon-based fieldeffect devices are currently being the basic structural element in a new generation of micro biosensors; they provide a lot of potential advantages such as small size and weight, fast response, high reliability, low output impedance, the possibility of automatic packaging at wafer level, on-chip integration of biosensor arrays and a signal processing scheme with the future prospect of low-cost mass production of portable microanalysis systems; moreover, their possible field of applications reaches from medicine, biotechnology and environmental monitoring through food and drug industries to defence and security. This paper gives a review of recent and significant advances in the research and development of BioFETs. In planing this review, we have chosen to focus mainly upon developments occurring during the last six years (from 1995 to the end of 2001). A computer search of the Science Citation Index has found that more than 400 publications concerning ISFETs and BioFETs have appeared from January 1995 to December 2001, indicating the intensity of research activities devoted to this important task. This review is in general limited to journal articles and usually does not include patents, conference proceedings, reports or PhD theses. Some references to important works reported prior to 1995 have also been added to provide additional source material. The review is organised as follows: The principles of the ISFET and BioFET are described in section 2. Recent advances in the development of various types of BioFETs are reviewed in section 3. Here, some examples of current applications of BioFETs are presented, too. Concluding points and future prospects of BioFETs are discussed in section 4. Michael J. Schöning was born in Bruchsal, Germany, in 1962. He received his diploma in 1989 and Ph.D. in 1993, both in electrical engineering, from the Technical University (TH) Karlsruhe. In 1989 he joined the Institute of Radiochemistry at the Research Centre Karlsruhe, Germany. Since 1993 he has been with the Institute of Thin Films and Interfaces at the Research Centre Jülich, and since 1999 he has been a Professor of applied physics at the University of the Applied Sciences Aachen, Germany. His research interests include silicon-based chemical and biological sensors, thin film techniques, solid-state physics, semiconductor devices and microsystem technology.

/pdf/recent-advances-in-biologically-sensitive-field-effect-1s078k27t4.pdf

Recent advances in biologically sensitive field-effect transistors (BioFETs)

Electrically–transduced sensors, with their simplicity and compatibility with standard electronic technologies, produce signals that can be efficiently acquired, processed, stored, and analyzed. Two dimensional (2D) nanomaterials, including graphene, phosphorene (BP), transition metal dichalcogenides (TMDCs), and others, have proven to be attractive for the fabrication of high–performance electrically-transduced chemical sensors due to their remarkable electronic and physical properties originating from their 2D structure. This review highlights the advances in electrically-transduced chemical sensing that rely on 2D materials. The structural components of such sensors are described, and the underlying operating principles for different types of architectures are discussed. The structural features, electronic properties, and surface chemistry of 2D nanostructures that dictate their sensing performance are reviewed. Key advances in the application of 2D materials, from both a historical and analytical pers...

Electrically-Transduced Chemical Sensors Based on Two-Dimensional Nanomaterials

Piezoelectric resonators have been in use as mass-sensing devices for almost half a century. More recently it was recognized that shifts in frequency and bandwidth can come about by a diverse variety of interactions with the sample. The classical "load" consists of a thin film, which shifts the resonance frequency due to its inertia. Other types of loading include semi-infinite viscoelastic media, rough objects contacting the crystal via isolated asperities, mechanically nonlinear contacts, and dielectric films. All these interactions can be analyzed within the small-load approximation. The small-load approximation provides a unified frame for interpretation and thereby opens the way to new applications of the QCM.

/pdf/viscoelastic-mechanical-and-dielectric-measurements-on-25k30gy3pe.pdf

Viscoelastic, mechanical, and dielectric measurements on complex samples with the quartz crystal microbalance

Microfabricated semiconductor devices are becoming increasingly relevant, also for the detection of biological and chemical quantities. Especially, the “marriage” of biomolecules and silicon technology often yields successful new sensor concepts. The fabrication techniques of such silicon-based chemical sensors and biosensors, respectively, will have a distinct impact in different fields of application such as medicine, food technology, environment, chemistry and biotechnology as well as information processing. Moreover, scientists and engineers are interested in the analytical benefits of miniaturised and microfabricated sensor devices. This paper gives a survey on different types of semiconductor-based field-effect structures that have been recently developed in our laboratory.

/pdf/playing-around-with-field-effect-sensors-on-the-basis-of-eis-6r9wzvcpkx.pdf

“Playing around” with Field-Effect Sensors on the Basis of EIS Structures, LAPS and ISFETs

Principles of electrochemical micro- and nano-system technologies

FUNDAMENTALS Electrochemical Microsystem Technologies: Principles Application for Homogenous Electrochemistry: Measurements of Fast Reaction Kinetics Fundamentals of Scanning Electrochemical Microscopy Electrochemical Microcells and Surface Analysis Application of Optical Micro-Methods and Lasers in Electrochemistry Nucleation and Growth in Microsystem Technology MICROPATTERNING High Resolution Lithography Advanced Plating Technology for Electronics Packaging Micro-Electroforming of Miniaturized Devices for Chemical Applications INTEGRATION OF SYSTEMS Capacitors and Micropower Systems Batteries for Micropower Applications Micro Flow Systems for Chemical and Biochemical Applications Corrosion of Microsystems MICROANALYSIS AND MICROSENSORS Electrochemical Microanalysis Novel Approaches to Design Silicon-Based Field-Effect Sensors Miniaturization of Biosensors Scanning Probe Microscopy as an Analysis Tool Microelectrode Techniques for Characterization of Advanced Materials for Battery and Sensor Applications BIOLOGICAL SYSTEMS Microsystems For Biosensing Nucleic Acids and Immuno Proteins New Microelectrode Arrays for Biosensing Membrane Electroporation Multi-Barrelled Ion-Selective Microelectrodes: Measurements of Cell Volume, Membrane Potential, and Intracellular Ion Concentrations in Invertebrate Nerve Cells Nerve Cells And Lipid Vesicles On Silicon Chips - Considerations On Ionoelectronic Sensors

Electrochemical microsystem technologies

Sensitivity variation of the electrochemical quartz crystal microbalance in response to energy trapping

Sensor systems for multi-parameter detection in fluidics usually combine different sensors, which are designed to detect either a physical or (bio-)chemical parameter. Therefore, such systems include a more complicated fabrication technology and measuring set-up. In this work, an ISFET (ion-sensitive field-effect transistor), which is well known as a (bio-)chemical sensor, is utilized as transducer for the detection of both (bio-)chemical and physical parameters. A multifunctional hybrid module for the determination of two (bio-)chemical parameters (pH, penicillin concentration) and three physical parameters (temperature, flow velocity and flow direction) using only two sensor structures, an ion generator and a reference electrode, is realized and its performance has been investigated. Here, a multifunctionality of the sensor system is achieved by means of different sensor arrangements and/or different operation modes. A Ta2O5-gate ISFET was used as transducer for all sensors. A novel time-of-flight type ISFET-based flow-velocity (flow rate) and flow-direction sensor using in-situ electrochemical generation of chemical tracers is presented. Due to the fast response of the ISFET (usually in the millisecond range), an ISFET-based flow sensor is suitable for the measurement of the flow velocity in a wide range. With regard to practical applications, pH measurements with this ISFET were performed in rain droplets.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Field-effect-based multifunctional hybrid sensor module for the determination of both (bio-)chemical and physical parameters

In the semiconductor industry, structures down to 100 nm may be created by conventional mask lithography. To overcome this technological barrier, new tools have to be developed. Although electron-beam lithography can generate structures in this geometrical dimension, its disadvantages complicate a routine use. Scanning probe microscopies, on the other hand, are promising tools for the fabrication of nanometer sizes structures which are independent of these constraints. Several applications of scanning probe microscopes to nanolithography are reported. Their main disadvantages are their limitation to specific substrates like Silicon or Titanium, special resist like monolayer inorganic materials or low resist thicknesses not suitable for industrial use. We present a scanning probe technique which is able to create positive and negative structures on a conventional electron beam resist in development liquid. The tip of the scanning probe microscope is scanned in direct contact to the resist surface under a defined load force. With this technique we were able to create arbitrary 3D structures with widths between 80 nm and 80 micrometers and depths between 5 nm and 0.5 micrometers in e-beam resists. The main advantage of the presented technique is the fabrication of oblique structures in one step which cannot be done by any other lithography technique.

Nanolithography of positive and negative structures by scanning probe microscopy using force modulation

A new concept for silicon microsensors based on porous EIS lectrolyte-nsulator4emiconductor) structures is presented. The porous sensor was prepared by anoclic etching of n-doped silicon and subsequent deposition of a dielectric layer of Si02. Experimental conditions were investigated to realize a well-defined macroporous formation of the poroussilicon. To compare the chemical sensor properties with similar built-up pianar Si/Si02 structures, C/V (capacitance-oltage) measurements have been performed. The porous EIS structures have been characterized by SEM (Scanning Electron Microscopy), XPS (X-ray Photoelectron Spectroscopy) and cyclic voltammetiy. This solid-state technology allowsthe preparation oftransducer materials for pH microsensors. 1. INTRODUCTION Since the invention of the ISFET (Ion Sensitive Field Effect Transistor1) in 1970 the main effort in the development of chemical sensors is the combination of the advantages of silicon microelectronic technology with the properties of

J. Walter Schultze

Papers

Electrochemical microsystem technologies

Sensitivity variation of the electrochemical quartz crystal microbalance in response to energy trapping

Field-effect-based multifunctional hybrid sensor module for the determination of both (bio-)chemical and physical parameters

Nanolithography of positive and negative structures by scanning probe microscopy using force modulation

Investigations on porous silicon layers with regard to chemical microsensor applications