Search

Transistor-based sensors have been widely recognized to be highly sensitive and reliable for point-of-care/bed-side diagnosis. In this line, a range of cutting-edge technologies has been generated to elevate the role of transistors for biomolecule detection. Detection of a wide range of clinical biomarkers has been reported using various configurations of transistors. The inordinate sensitivity of transistors to the field-effect imparts high sensitivity toward wide range of biomolecules. This overview has gleaned the present achievements with the technological advancements using high performance transistor-based sensors. This review encloses transistors incorporated with a variety of functional nanomaterials and organic elements for their excellence in selectivity and sensitivity. In addition, the technological advancements in fabrication of these microdevices or nanodevices and functionalization of the sensing elements have also been discussed. The technological gap in the realization of sensors in transistor platforms and the resulted scope for research has been discussed. Finally, foreseen technological advancements and future research perspectives are described. [ABSTRACT FROM AUTHOR]

Programmability, fundamental to the computing of electronic systems, is traditionally achieved in processing and memory modules. Recently, the emergence of in‐sensor computing allows the programmability of the sensing modules and the process of raw data upon the sensor edge, which reduces data transport and energy consumption. Here, a programmable photodetector module with a tunable photoelectric response based on molybdenum sulfide (MoS2) metal‐oxide‐semiconductor (MOS) junction for visible detection is reported. The sensor takes advantage of the tunable band alignment at the MOS junction and generates an adjustable or even reversible out‐of‐plane photovoltaic effect with high efficiency. This work provides new device configurations to architect the programmability of the photodetectors, and pave the way toward in‐sensor computing at the application edge. [ABSTRACT FROM AUTHOR]

Currently, the power conversion efficiency (PCE) of inverted perovskite solar cells (PSCs) is still limited by reduced open-circuit voltage (V OC ), due to defect-induced charge recombination. Most studies focus on defect passivation and improving carrier transport through introducing passivating molecules or macroscopic physical fields. Herein, to mitigate energy level mismatch and recombination losses induced by interface defects, an interface electric-field passivation is introduced, employing the ordered arrangement of the dipole molecule benzenesulfonyl chloride (BC). An enhanced V OC is achieved without the introduction of an external physical field, owing to the interfacial dipole field effect and chemical passivation by BC. Subsequently, an inverted device with a PCE of 25.41% is obtained, alongside exceptional stability, retaining 95% of the initial efficiency after 1157 h. This work demonstrates the effective dipole-induced interfacial field-effect passivation in inverted PSCs and contributes to further advancements in the efficiency and stability of inverted devices., (© 2024 Wiley‐VCH GmbH.)

Impedance spectroscopy is an electrochemical technique widely used for the electrical characterization of the behavior of biomaterials in all kinds of biosensors. Field‐effect devices, and in particular ion‐sensitive field‐effect transistors (ISFETs), have been extensively studied as transducers for biosensing. They however have not been much analyzed with impedance spectroscopy, because they typically generate non‐Faradaic capacitance measurements, since there is no charge transfer through the insulating gate in contact with the liquid solution. We have recently experimentally shown that Faradaic‐like impedance spectroscopy spectra can be obtained with ISFET devices, allowing high‐sensitivity measurements for different pH and biomarker concentrations. In this paper, we report that both Faradaic‐like and non‐Faradaic impedance behavior can be well understood by a DC and small‐signal AC model of the ISFET working in different conditions. Faradaic‐like impedance measurements are described by the operation of the ISFET in subthreshold conditions. A Nyquist plot semicircle is obtained, corresponding to the transimpedance 1/gm of the ISFET in parallel to the gate capacitances. We show that this behavior is independent of the presence of membrane material on the gate surface. In these conditions, the change in the semicircle diameter for different pH or biomarker concentrations can be understood by the change of 1/gm corresponding to a threshold voltage shift of the transistor. This description is illustrated with our recent results for pH measurements and the detection of tumor necrosis factor‐α with functionalized devices in standard solutions in the concentration range of 1–20 pg/ml. The use of the impedance spectroscopy technique takes advantage of the exponential behavior of the gm(VGS) curves in the subthreshold (weak inversion) operation of the ISFET. This results in a large signal amplification, where a small change in the threshold voltage results in a large change in the impedance spectrum, thus achieving an increased precision in the measurement of the device response to changes in the analyte concentration. [ABSTRACT FROM AUTHOR]

The concept of tumor field effect implies that cancer is a systemic disease with its impact way beyond the visible tumor confines. For instance, in Glioblastoma (GBM), an aggressive brain tumor, the increase in intracranial pressure due to tumor burden often leads to brain herniation and poor outcomes. Our work is based on the rationale that highly aggressive tumors tend to grow uncontrollably, leading to pronounced biomechanical tissue deformations in the normal parenchyma, which when combined with local morphological differences in the tumor confines on MRI scans, will comprehensively capture tumor field effect. Specifically, we present an integrated MRI-based descriptor, radiomic-Deformation and Textural Heterogeneity (r-DepTH). This descriptor comprises measurements of the subtle perturbations in tissue deformations throughout the surrounding normal parenchyma due to mass effect. This involves non-rigidly aligning the patients’ MRI scans to a healthy atlas via diffeomorphic registration. The resulting inverse mapping is used to obtain the deformation field magnitudes in the normal parenchyma. These measurements are then combined with a 3D texture descriptor, Co-occurrence of Local Anisotropic Gradient Orientations (COLLAGE), which captures the morphological heterogeneity and infiltration within the tumor confines, on MRI scans. In this work, we extensively evaluated r-DepTH for survival risk-stratification on a total of 207 GBM cases from 3 different cohorts (Cohort 1 (${n}{1} = {53}$), Cohort 2 (${n}{2} = {75}$), and Cohort 3 (${n}{3} = {79}$)), where each of these three cohorts was used as a training set for our model separately, and the other two cohorts were used for testing, independently, for each training experiment. When employing Cohort 1 for training, r-DepTH yielded Concordance indices (C-indices) of 0.7 and 0.65, hazard ratios (HR) and Confidence Intervals (CI) of 10 (6 − 19) and 5 (3 − 8) on Cohorts 2 and 3, respectively. Similarly, training on Cohort 2 yielded C-indices of 0.6 and 0.7, HR and CI of 1 (0.7 − 2) and 3 (2 − 5) on Cohorts 1 and 3, respectively. Finally, training on Cohort 3 yielded C-indices of 0.75 and 0.63, HR and CI of 24 (10 − 57) and 12 (6 − 21) on Cohorts 1 and 2, respectively. Our results show that r-DepTH descriptor may serve as a comprehensive and a robust MRI-based prognostic marker of disease aggressiveness and survival in solid tumors. [ABSTRACT FROM AUTHOR]

The inferior electrical contact to two-dimensional (2D) materials is a critical challenge for their application in post-silicon very large-scale integrated circuits. Electrical contacts were generally related to their resistive effect, quantified as contact resistance. With a systematic investigation, this work demonstrates a capacitive metal-insulator-semiconductor (MIS) field-effect at the electrical contacts to 2D materials: The field-effect depletes or accumulates charge carriers, redistributes the voltage potential, and gives rise to abnormal current saturation and nonlinearity. On one hand, the current saturation hinders the devices' driving ability, which can be eliminated with carefully engineered contact configurations. On the other hand, by introducing the nonlinearity to monolithic analog artificial neural network circuits, the circuits' perception ability can be significantly enhanced, as evidenced using a coronavirus disease 2019 (COVID-19) critical illness prediction model. This work provides a comprehension of the field-effect at the electrical contacts to 2D materials, which is fundamental to the design, simulation, and fabrication of electronics based on 2D materials. [ABSTRACT FROM AUTHOR]

Nanowires require surface passivation due to their inherent large surface to volume ratio. We investigate the effect of embedding InP nanowires in different oxides with respect to surface passivation by use of electron beam induced current measurements enabled by a nanoprobe based system inside a scanning electron microscope. The measurements reveal remote doping due to fixed charge carriers in the passivating POx/Al2O3 shell in contrast to results using SiOx. We used time-resolved photoluminescence to characterize the lifetime of charge carriers to evaluate the success of surface passivation. In addition, spatially resolved internal quantum efficiency simulations support and correlate the two applied techniques. We find that atomic-layer deposited POx/Al2O3 has the potential to passivate the surface of InP nanowires, but at the cost of inducing a field-effect on the nanowires, altering their electrostatic potential profile. The results show the importance of using complementary techniques to correctly evaluate and interpret processing related effects for optimization of nanowire-based optoelectronic devices. [ABSTRACT FROM AUTHOR]

The ternary complex photocatalysts of BiOIO 3 /g-C 3 N 4 /MoS 2 by solvent-exfoliation method was synthesized for the first time. In the typical procedure, the BiOIO 3 /g-C 3 N 4 was obtained via hydrothermal synthesis technique, and then the BiOIO 3 /g-C 3 N 4 /MoS 2 photocatalysts were prepared via ultrasonic solvent-exfoliation method from bulk commercial MoS 2 in the alcohol solution. The samples of BiOIO 3 /g-C 3 N 4 /MoS 2 were analyzed by PL, XRD and other characterization analysis methods. The photocatalytic activity of the as-prepared samples was investigated by removing gas phase mercury irradiation under visible light. The as-prepared BCM-0.3 exhibits excellent photocatalytic performance, being with the highest efficiency of 70.58%. Owing to the electronic channels of field-effect, an internal electric field was formed through the corresponding band-gap engineering, improving photocatalytic reaction. Besides, the excellent activity of the ternary photocatalysts BiOIO 3 /g-C 3 N 4 /MoS 2 is attributed to heterostructure between BiOIO 3 /g-C 3 N 4 and MoS 2 , which enlarges spectral response and improved separation efficiency of charge carriers, and MoS 2 -composing, which provides more active sites for catalytic oxidation. In addition, the as-prepared samples with excellent photocatalytic performance also offer a perspective insight into the hydrogen evolution, CO 2 conversion and degradation of organic pollutants. • The ternary compound photocatalyst of BiOIO 3 /g-C 3 N 4 /MoS 2 by solvent-exfoliation method was synthesized for the first time. • The as-prepared ternary nanocomposite exhibits more excellent photoactivity compared with BiOIO 3 /g-C 3 N 4. • The possible photoinduced charges transfer mechanism and photocatalytic reaction mechanism were proposed. [ABSTRACT FROM AUTHOR]

The aim of this paper is to present the out-of-equilibrium body potential behaviour in the Ψ-MOSFET configuration. Consistent measurements in this experimental setup succeeded in providing a substantial understanding of its characteristics in the depletion region. The final objective of this work is to envision this new measurement technique for biochemical sensor applications. Among its advantages, the most important are its simplicity, the good sensitivity, the measurement of a potential instead of a current and the low bias needed for detection compared to the conventional drain current measurements. [ABSTRACT FROM AUTHOR]

We report to apply Al nanoparticles (NPs) to enhance the photovoltaic response of crystalline- or c-Si solar cell from the ultraviolet (UV) throughout the visible and near infrared (NIR) regimes. Al NPs were induced by solid thermal annealing and embedded in a SiO 2 layer that was to passivate the front side of solar cell. Upon the excitation of surface plasmons (SPs) on the Al NPs under light illumination, an enhancement of broadband absorption of the solar cell was observed. The incorporation of Al NPs led to a relative 13.8% increase in photoelectric conversion efficiency of c-Si solar cell, and an external quantum efficiency enhancement from the UV throughout the visible and NIR regimes. The improvement of c-Si solar cell performance was attributed to both effects of absorption and scattering by SPs. [ABSTRACT FROM AUTHOR]

Copyright of Technisches Messen is the property of De Gruyter and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Stacked van der Waals (vdW) heterostructures where semiconducting two-dimensional (2D) materials are contacted by overlaid graphene electrodes enable atomically thin, flexible electronics. We use first-principles quantum transport simulations of graphene-contacted MoS2 devices to show how the transistor effect critically depends on the stacking configuration relative to the gate electrode. We can trace this behavior to the stacking-dependent response of the contact region to the capacitive electric field induced by the gate. The contact resistance is a central parameter and our observation establishes an important design rule for ultrathin devices based on 2D atomic crystals. [ABSTRACT FROM AUTHOR]

A thieno [3,2-b] thiophene-based planar liquid crystal molecule, C12-PTTT, which possesses the characteristics of an organic field-effect transistor (OFET), was synthesised and its mesomorphic properties were studied by polarising optical microscopy and differential scanning calorimetry. A wide temperature range for a highly oriented smectic phase was observed. OFET devices made under various conditions, such as self-assembled monolayer treatment and alignment treatment, and with micro-channel structures, were fabricated to measure the electrical properties. Among different OFET device conditions, the best electric carrier mobility for C12-PTTT was 0.038 cm2 V−1 s−1. [ABSTRACT FROM AUTHOR]

Novel physical phenomena arising at the interface of complex oxide heterostructures offer exciting opportunities for the development of future electronic devices. Using the prototypical LaAlO3/SrTiO3 interface as a model system, we employ a single-step lithographic process to realize gate-tunable Josephson junctions through a combination of lateral confinement and local side gating. The action of the side gates is found to be comparable to that of a local back gate, constituting a robust and efficient way to control the properties of the interface at the nanoscale. We demonstrate that the side gates enable reliable tuning of both the normal-state resistance and the critical (Josephson) current of the constrictions. The conductance and Josephson current show mesoscopic fluctuations as a function of the applied side gate voltage, and the analysis of their amplitude enables the extraction of the phase coherence and thermal lengths. Finally, we realize a superconducting quantum interference device in which the critical currents of each of the constriction-type Josephson junctions can be controlled independently via the side gates. [ABSTRACT FROM AUTHOR]

Recently synthesized small molecule tellurophenes containing ring-appended pinacolboronate (BPin) side groups possess remarkable guest-free air-stable solid-state phosphorescence, structure-based color-tunability and aggregation induced enhanced emission. The charge transport, doping and luminescence behavior of thin transparent films of a tellurophene with BPin groups positioned at the 2,5-positions ( B-Te-6-B ) was investigated. Film formation played a critical role in determining the hole mobility and the photoluminescence (PL) lifetime. Drop-coated films showed the strongest crystallinity, the highest PL quantum yields and a hole mobility ( μ p ) of 1.1 × 10 −4 cm 2 V −1 s −1 , which places tellurophenes in a select group of high mobility phosphorescent emitters. B-Te-6-B was also found to spontaneously form high aspect-ratio microwires upon drop-casting from supersaturated solutions. Oxidative doping in solution by a N(C 6 H 4 Br) 3 [SbCl 6 ]/LiNTf 2 reagent combination (Tf = SO 2 CF 3 ) increased conductivity by 2-4 orders of magnitude without inducing a color change in the films, while exposure to iodine vapor induced a dramatic change in color together with a 4-6 order of magnitude change in the conductivity. The optical transparency, facile electrical doping and relatively high hole mobilities of B-Te-6-B in solution processed thin films offer promise for the use of tellurophenes as host-free emissive layers and hole transport layers in organic optoelectronic devices. [ABSTRACT FROM AUTHOR]

We demonstrate localization and field-effect spatial control of the plasmon resonance in semiconductor nanostructures, using scattering-type scanning near-field optical microscopy in the mid-infrared region. We adopt InAs nanowires embedding a graded doping profile to modulate the free carrier density along the axial direction. Our near-field measurements have a spatial resolution of 20 nm and demonstrate the presence of a local resonant feature whose position can be controlled by a back-gate bias voltage. In the present implementation, field-effect induces a modulation of the free carrier density profile yielding a spatial shift of the plasmon resonance of the order of 100 nm. We discuss the relevance of our electrically tunable nanoplasmonic architectures in view of innovative optoelectronic devices concepts. [ABSTRACT FROM AUTHOR]

In this paper, we examine the theoretical basis for using passive unheated electron field emitters to control hazardous levels of spacecraft charging. We present the experimental evidence related to the capabilities of passive and low-power active field emitters. The concept of passive field emitters is detailed looking at their characteristics and location on a model satellite typical of a commercial geostationary satellite. The assessment is performed by means of numerical simulations. The generation and extraction of electrons is simulated at micrometric scale. Their flow is modeled at spacecraft scale to assess spacecraft absolute and differential charging alleviation. The system shows good promise limiting the inverted voltage gradient situations, observed especially on solar panels where cover glasses are more positive than solar cells. This situation is known as very risky in flight, possibly leading to sustained secondary arcing powered by the photovoltaic solar arrays themselves. Finally, we review how existing design practice would be modified by the presence of such passive emitters. [ABSTRACT FROM PUBLISHER]

Conventional methods for enzyme immobilisation onto sensor surfaces often use dip-, drop- or spin-coating techniques. In this study, a nano-spotting technique has been investigated for a patterned, spatially resolved deposition of enzymes onto a capacitive field-effect electrolyte-insulator-semiconductor (EIS) sensor and compared with the drop-coating method. Therefore, four different sensor arrangements covered with immobilised penicillinase as a model enzyme have been studied: (i) The sensor surface fully drop-coated, (ii) half drop-coated, (iii) half nano-spotted and (iv) fully nano-spotted with penicillinase. The sensors have been electrochemically characterised in pH buffers and penicillin solutions by means of impedance-spectroscopy, capacitance-voltage and constant-capacitance methods. [ABSTRACT FROM AUTHOR]

Surface recombination represents a handicap for high-efficiency solar cells. This is especially important for nanowire array solar cells, where the surface-to-volume ratio is greatly enhanced. Here, the effect of different passivation materials on the effective recombination and on the device performance is experimentally analyzed. Our solar cells are large area top-down axial n-p junction silicon nanowires fabricated by means of Near-Field Phase-Shift Lithography (NF-PSL). We report an efficiency of 9.9% for the best cell, passivated with a SiO/SiN stack. The impact of the presence of a surface fixed charge density at the silicon/oxide interface is studied. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Gold-active-layer transistors have been recently reported in the literature. The device terminal characteristics show a power-law dependence of the drain current with the gate overdrive voltage. A study of the theoretical transition frequency shows that circuits realized with these devices can operate at frequencies up to three orders of magnitude higher than if realized with standard MOS transistors of similar channel length. To investigate the device application in circuit design, a simple device model was implemented in the CADENCE Spectre analog environment and a ring oscillator was simulated. [ABSTRACT FROM AUTHOR]

Abstract: For the development of new biopolymers and implantable biomedical devices with predicted biodegradability, simple, non-destructive, fast and inexpensive techniques capable for real-time in situ testing of the degradation kinetics of polymers are highly appreciated. In this work, a capacitive field-effect electrolyte–insulator–semiconductor (EIS) sensor has been applied for real-time in situ monitoring of degradation of thin poly(d,l-lactic acid) (PDLLA) films over a long-time period of one month. Generally, the polymer-modified EIS (PMEIS) sensor is capable of detecting any changes in the bulk, surface and interface properties of the polymer (e.g., thickness, coverage, dielectric constant, surface potential) induced by degradation processes. The time-dependent capacitance–voltage (C–V) characteristics of PMEIS structures were used as an indicator of the polymer degradation. To accelerate the PDLLA degradation, experiments were performed in alkaline buffer solution of pH 10.6. The results of these degradation measurements with the EIS sensor were verified by the detection of lactic acid (product of the PDLLA degradation) in the degradation medium. In addition, the micro-structural and morphological changes of the polymer surface induced by the polymer degradation have been systematically studied by means of scanning-electron microscopy, atomic-force microscopy, optical microscopy, and contact-angle measurements. [Copyright &y& Elsevier]

The semiconductor field-effect platform represents a powerful tool for detecting the adsorption and binding of charged macromolecules with direct electrical readout. In this work, a capacitive electrolyte-insulator-semiconductor (EIS) field-effect sensor consisting of an Al-p-Si-SiO structure has been applied for real-time in situ electrical monitoring of the layer-by-layer formation of polyelectrolyte (PE) multilayers (PEM). The PEMs were deposited directly onto the SiO surface without any precursor layer or drying procedures. Anionic poly(sodium 4-styrene sulfonate) and cationic weak polyelectrolyte poly(allylamine hydrochloride) have been chosen as a model system. The effect of the ionic strength of the solution, polyelectrolyte concentration, number and polarity of the PE layers on the characteristics of the PEM-modified EIS sensors have been studied by means of capacitance-voltage and constant-capacitance methods. In addition, the thickness, surface morphology, roughness and wettabilityof the PE mono- and multilayers have been characterised by ellipsometry, atomic force microscopy and water contact-angle methods, respectively. To explain potential oscillations on the gate surface and signal behaviour of the capacitive field-effect EIS sensor modified with a PEM, a simplified electrostatic model that takes into account the reduced electrostatic screening of PE charges by mobile ions within the PEM has been proposed and discussed. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Abstract: In this work, we present a novel characterization technique for the analysis of Si surface passivation layers, using a photoluminescence imaging setup. In this technique the effective lifetime of passivated Si wafers is measured while applying an external bias over a rear side dielectric film. We demonstrate that this method can be used to analyze the passivation of silicon surfaces in inversion, depletion and accumulation conditions. In this paper the method is illustrated by characterization of a-SiN x :H passivation layers deposited by plasma enhanced chemical vapor deposition. The characterization results are interpreted both in the framework of the extended Shockley–Read–Hall theory and by PC1D simulations. For the a-SiN x :H layers, the effective surface recombination velocity parameter is found to be 5 to 7 times larger for electrons than for holes and the fixed insulator charge density is found to be cm−2 under illumination, in agreement with results from capacitance–voltage measurements. [Copyright &y& Elsevier]

Charge density wave (CDW) under an applied electric field in constraint geometry experience stresses, which can easily exceed a plastic threshold. The stress is resolved by the ground state reconstruction which proceed via creation of topological defects like solitons and dislocations-the CDW vortices. These states can be observed experimentally either in average at macroscopic scales of X-ray and multijunction space resolved studies, at mesoscopic scales of coherent X-ray micro-diffraction and nano-junctions or individually as by the STM. Here, we report numerical modeling taking into account multiple fields in their mutual nonlinear interactions: the phase and the amplitude of the CDW order parameter, distributions of the electric field, of the density and the current of normal carriers. Following events of creation and the subsequent evolution of dislocations, we find that vortices are formed in the junction when the voltage across, or the current through, exceed a threshold. The number of vortices remnant in the reconstructed ground state increases stepwise-in agreement with experiments. The vortex core concentrates the voltage drop across the junction giving rise to observed peaks of the interlayer tunneling. The studied reconstruction in junctions of CDWs may be relevant to modern efforts of the field-effect transformations in other correlated electronic systems. [ABSTRACT FROM AUTHOR]

Abstract: We report on studies of stationary states and their transient dynamic for an incommensurate charge density wave (ICDW) in a restricted geometry of two spatial dimensions. The model takes into account multiple fields in mutual nonlinear interactions: the amplitude and the phase of the complex order parameter, and distributions of the electric and chemical potentials, of the density and the current of normal carriers. We observed spontaneous formation of vortices (the ICDW dislocations), and followed events of their creation and the subsequent evolution. The vortices appear when the voltage across, or the current through, the sample exceed a threshold. The number of vortices remnant in the reconstructed stationary state increases stepwise – in agreement with experiments, while a much greater number of vortices appears during the intermediate transient states. The vortex core concentrates the electric dipole leading to sharp drops of the electric and chemical potentials across the core. That can lead to enhanced inter-layer tunneling making the core to be a self-tuned microscopic tunneling junction. The results are applied to experiments on nano-fabricated mesa-junctions. They also appeal to modern efforts of the field-effect transformations in correlated electronic systems. [Copyright &y& Elsevier]

Abstract: We report a comprehensive noncontact approach to measurement of the field-effect passivation of emitters for p and n-type base silicon solar cells. The corona charge-voltage technique, extensively used in silicon IC fabrication lines, is utilized in an automated sequence with two complementary measurements that monitor charge induced changes of recombination in the emitter. Quasi-steady-state microwave photoconductance decay, QSS-μPCD measures decay lifetime τeff, the injection level, Δn and the emitter saturation current, J0. UV and blue ac-surface photovoltage (UV-SPV) gives a passivation indicator analogous to short wavelength quantum efficiency. Field-effect characteristics of τeff, Seff, J0, and UV-SPV are presented for symmetrical n+and p+emitter test wafers that quantify the effect of charge, polarity and differences between n+and p+emitters. New findings include field effect hysteresis and charging induced emitter degradation phenomenon analogous to stress induced degradation in MOS devices. [Copyright &y& Elsevier]

Abstract: An array of individually addressable nanoplate field-effect capacitive (bio-)chemical sensors based on an SOI (silicon-on-insulator) structure has been developed. The isolation of the individual capacitors was achieved by forming a trench in the top Si layer with a thickness of 350nm. The realized sensor array allows addressable biasing and electrical readout of multiple nanoplate EISOI (electrolyte–insulator–silicon-on-insulator) capacitive biosensors on the same SOI chip as well as differential-mode measurements. The feasibility of the proposed approach has been demonstrated by realizing sensors for the pH and penicillin concentration detection as well as for the label-free electrical monitoring of polyelectrolyte multilayers formation and DNA (deoxyribonucleic acid)-hybridization event. A potential change of ∼120mV has been registered after the DNA hybridization for the sensor immobilized with perfectly matched single-strand DNA, while practically no signal changes have been observed for a sensor with fully mismatched DNA. The realized examples demonstrate the potential of the nanoplate SOI capacitors as a new basic structural element for the development of different types of field-effect biosensors. [ABSTRACT FROM AUTHOR]

Abstract: Urinary stone formation has been evolved to a widespread disease during the last years. The reason for the formation of urinary stones are little crystals, mostly composed of calcium oxalate, which are formed in human kidneys. The early diagnosis of the risk for urinary stone formation of patients can be determined by the “Bonn-Risk-Index” method based on the potentiometric detection of the Ca2+-ion concentration and an optical determination of the triggered crystallisation of calcium oxalate in unprocessed urine. In this work, miniaturised capacitive field-effect EMIS (electrolyte-membrane-insulator-semiconductor) sensors have been developed for the determination of the Ca2+-ion concentration in human native urine. The Ca2+-sensitive EMIS sensors have been systematically characterised by impedance spectroscopy, capacitance–voltage and constant–capacitance method in terms of sensitivity, signal stability and response time in both CaCl2 solutions and in native urine. The obtained results demonstrate the suitability of EMIS sensors for the measurement of the Ca2+-ion concentration in native urine of patients. [Copyright &y& Elsevier]

Abstract: In this study, a concept for a silicon-based modular solid-state sensor system for inline multi-parameter monitoring of cell-culture fermentation processes is presented. The envisaged multi-parameter sensor system consists of two identical sensor modules and is intended for continuous quantification of up to five (bio-)chemical and physical parameters, namely, glucose and glutamine concentration, pH value, electrolyte conductivity and temperature by applying different transducer principles and/or different operation modes. Experimental results for the field-effect electrolyte-insulator-semiconductor (EIS) sterilisable pH sensor and electrolyte conductivity sensor based on interdigitated electrodes are presented. The ongoing autoclaving does not have any significant impact on the pH-sensitive properties of a Ta2O5-gate EIS sensor. Even after 30 autoclaving cycles, the pH sensors show a clear pH response and nearly linear calibration curve with a slope of 57±1mV/pH. Additional scanning electron microscopy and ellipsometric investigations do not show any visible surface degradation or changes in the thickness of the pH-sensitive Ta2O5 layer. The preliminary results demonstrate the suitability of the developed EIS sensor for an inline pH measurement during a fermentation process. In addition, interdigitated electrodes of different geometries serving as electrolyte conductivity sensor have been tested for measurements in relatively high ionic-strength solutions. [Copyright &y& Elsevier]

Abstract: A capacitive field-effect EDIS (electrolyte–diamond–insulator–semiconductor) sensor with improved pH and penicillin sensitivity has been realised using a nanocrystalline-diamond (NCD) film as sensitive gate material. The NCD growth process on SiO2 as well as an additional surface treatment in oxidising medium have been optimised to provide high pH-sensitive, non-porous O-terminated films without damage of the underlying SiO2 layer. The surface morphology of O-terminated NCD thin films and the layer structure of EDIS sensors have been studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) methods. To establish the relative coverage of the surface functional groups generated by the oxidation of NCD surfaces, X-ray photoelectron spectroscopy analysis was carried out. The hydrophilicity of NCD thin films has been studied by water contact-angle measurements. A nearly Nernstian pH sensitivity of 54–57mV/pH has been observed for O-terminated NCD films treated in an oxidising boiling mixture for 80min and in oxygen plasma. The high pH-sensitive properties of O-terminated NCD have been used to develop an EDIS-based penicillin biosensor. A freshly prepared penicillin biosensor possesses a high sensitivity of 85mV/decade in the concentration range of 0.1–2.5mM penicillin G. The lower detection limit is 5μM. [Copyright &y& Elsevier]

Abstract: A new LAPS (light-addressable potentiometric sensor) set-up will be introduced, in which the light sources are miniaturised by the utilisation of a VCSEL (vertical-cavity surface-emitting laser) array to increase the measurement spot density. An FPGA (field-programmable gate array) is used to generate modulation signals for an individual illumination of each measurement spot of the LAPS. The new set-up can operate a large number of measurement spots simultaneously by reading out the sum-photocurrent and separate the signals of the individual measurement spots by FFT analysis. The frequency, amplitude and offset of the modulation signal can be configured for each measurement spot programmatically. [Copyright &y& Elsevier]