New Class Of Sensors Research Articles

Distributed Feedback Laser Biosensor Noise Reduction

Label-free biosensors based upon detection of shifts in the emission wavelength, which occur when biological analytes are adsorbed on the surface of a solid-state laser, represent an important new class of sensors that can simultaneously provide high sensitivity and high resolution. We report on a signal processing approach that enables detection of lasing wavelength shifts as small as Δλ ~ 1.5 pm from a distributed feedback laser biosensor (DFBLB) fabricated upon a flexible plastic substrate and incorporated into standard-format microplates. Because the DFBLB can be optically pumped in a pulsed mode at a repetition rate that is substantially faster than the rate of biomolecular binding interactions, noise may be reduced through the ability to average multiple independent readings through integration of many lasing spectra within a single spectral integration period, and to subsequently use boxcar averaging to collapse multiple readings in a time sequence to a single time point. We have observe that the DFBLB occasionally produces nonclassical output spectra that can lead to an increase in wavelength shift noise, and therefore we implement a statistical metric to automatically determine whether an acquired spectrum should be discarded from analysis. The combined approaches are used to demonstrate the ability to detect a protein-protein interaction with an analyte concentration that would not otherwise be observable over background noise.

Electron-Tunneling Modulation in Percolating Network of Graphene Quantum Dots: Fabrication, Phenomenological Understanding, and Humidity/Pressure Sensing Applications

The two-dimensional (2D) electron cloud, flexible carbon-carbon bonds, chemical modifiability, and size-dependent quantum-confinement and capacitance makes graphene nanostructures (GN) a widely tunable material for electronics. Here we report the oxidation-led edge-roughening and cleavage of long graphene nanoribbons (GNRs) (150 nm wide) synthesized via nanotomy (nanoscale cutting) of graphite (with 2 nm edged diamond knife) to produce graphene quantum dots (GQD). These GQDs (~100-200 nm) selectively interfaced with polyelectrolyte microfiber (diameter = 2-20 μm) form an electrically percolating-network exhibiting a characteristic Coulomb blockade signature with a dry tunneling distance of 0.58 nm and conduction activation energy of 3 meV. We implement this construct to demonstrate the functioning of humidity and pressure sensors and outline their governing model. Here, a 0.36 nm decrease in the average tunneling-barrier-width between GQDs (tunneling barrier = 5.11 eV) increases the conductivity of the device by 43-fold. These devices leverage the modulation in electron tunneling distances caused by pressure and humidity induced water transport across the hygroscopic polymer microfiber (Henry's constant = 0.215 Torr(-1)). This is the foremost example of GQD-based electronic sensors. We envision that this polymer-interfaced GQD percolating network will evolve a new class of sensors leveraging the low mass, low capacitance, high conductivity, and high sensitivity of GQD and the interfacial or dielectric properties of the polymer fiber.

Theory of signal and noise in double-gated nanoscale electronic pH sensors

The maximum sensitivity of classical nanowire (NW)-based pH sensors is defined by the Nernst limit of 59 mV/pH. For typical noise levels in ultra-small single-gated nanowire sensors, the signal-to-noise ratio is often not sufficient to resolve pH changes necessary for a broad range of applications. Recently, a new class of double-gated devices was demonstrated to offer apparent "super-Nernstian" response (>59 mV/pH) by amplifying the original pH signal through innovative biasing schemes. However, the pH-sensitivity of these nanoscale devices as a function of biasing configurations, number of electrodes, and signal-to-noise ratio (SNR) remains poorly understood. Even the basic question such as "Do double-gated sensors actually resolve smaller changes in pH compared to conventional single-gated sensors in the presence of various sources of noise?" remains unanswered. In this article, we provide a comprehensive numerical and analytical theory of signal and noise of double-gated pH sensors to conclude that, while the theoretical lower limit of pH-resolution does not improve for double-gated sensors, this new class of sensors does improve the (instrument-limited) pH resolution.

Smart “Stick-on” Sensors for the Smart Grid

Rapid increase in electric power demand, introduction of RPS mandates, and a push towards electrification in the transportation sector is expected to increase power system stresses and disturbances. To tackle these power system issues and maintain high system reliability, it is essential to have information about the condition of assets present on the grid. Presently, due to the absence of low cost flexible grid wide monitoring solutions, complete information of the system is not achievable. This paper deals with the development of a new class of sensors called the smart “stick-on” sensors. These are low cost, self-powered, universal sensors that provide a flexible monitoring solution for grid assets. These sensors can be mass deployed due to low cost, need low maintenance as they are self-powered, and can be used for monitoring a variety of grid assets. This paper also presents the details on the network architecture, interoperability and integration, and different design aspects of the stick-on sensor, such as novel energy harvesting techniques, power management, wide operating range, and reliability. It is envisioned that the smart stick-on sensors shall be an enabling technology for monitoring a variety of grid assets and prove to be an essential element of the Smart Grid.

Method to Have Multilayer Thermal Insulation Provide Damage Detection

Method to Have Multilayer Thermal Insulation Provide Damage Detection

RF Front-End Test Using Built-in Sensors

This article proposes a new class of sensors for built-in test in RF devices. These sensors are placed in close proximity to the DUT on the same substrate without being electrically connected to it. Instead, they monitor it by virtue of being subjected to the same process variations. The authors also describe other types of sensors they have studied, including DC probes, an envelope detector, and a current sensor.

A novel approach for high precision rapid potentiometric titrations: Application to hydrazine assay

We propose a high precision rapid personal computer (PC) based potentiometric titration technique using a specially designed mini-cell to carry out redox titrations for assay of chemicals in quality control laboratories attached to industrial, R&D, and nuclear establishments. Using this technique a few microlitre of sample (50-100 μl) in a total volume of ~2 ml solution can be titrated and the waste generated after titration is extremely low comparing to that obtained from the conventional titration technique. The entire titration including online data acquisition followed by immediate offline analysis of data to get information about concentration of unknown sample is completed within a couple of minutes (about 2 min). This facility has been created using a new class of sensors, viz., pulsating sensors developed in-house. The basic concept in designing such instrument and the salient features of the titration device are presented in this paper. The performance of the titration facility was examined by conducting some of the high resolution redox titrations using dilute solutions--hydrazine against KIO(3) in HCl medium, Fe(II) against Ce(IV) and uranium using Davies-Gray method. The precision of titrations using this innovative approach lies between 0.048% and 1.0% relative standard deviation in different redox titrations. With the evolution of this rapid PC based titrator it was possible to develop a simple but high precision potentiometric titration technique for quick determination of hydrazine in nuclear fuel dissolver solution in the context of reprocessing of spent nuclear fuel in fast breeder reactors.

Genetically encoded force sensors for measuring mechanical forces in proteins.

THERE ARE THREE SOURCES OF FREE ENERGY FOR CELLS: chemical potential, electrical potential and mechanical potential. There is little known about the last one since there have not been simple ways to measure stress in proteins in cells. we have now developed genetically encoded force sensors to assess the stress in fibrous proteins in living cells. These FReT based fluorescence sensors can be read out at video rates and provide real time maps of the stress distribution in cells, tissues and animals. The sensors can be inserted into specific proteins and in general do not disturb the normal function or anatomy. The original sensors used mutant GFPs linked by elastic linkers. These sensors provide a linear output with applied stress but the response is linear in strain. To improve contrast and dynamic range we have now developed a new class of sensors that are smaller making them less invasive, and have much higher intrinsic sensitivity since force modulates the angle between the donor and acceptor much more than the distance between them. Known as cpstFRET, the probe shows improved biocompatibility, wider dynamic range and higher sensitivity.

Minimal cross-sensitivity to humidity during ethanol detection bySnO2–TiO2 solid solutions

A nanocomposite material is presented that optimally combines the excellent gas sensitivity ofSnO2 and theselectivity of TiO2. Nanostructured, rutile titanium–tin oxide solid solutions up to 81.5% Ti, as determinedby x-ray diffraction, are made by scalable spray combustion (flame spray pyrolysis)of organometallic precursor solutions, directly deposited and in situ annealedonto sensing electrodes in one step. Above that content, segregation of anataseTiO2 takes place.It was discovered that at low titanium contents (less than 5 Ti%),these materials exhibit higher sensitivity to ethanol vapor than pureSnO2 and, in particular, limited cross-sensitivity to relative humidity, a long standingchallenge for metal oxide gas sensors. These solid solutions are aggregatednanoparticles with an enhanced presence of Ti on their surface as indicatedby Raman and IR-spectroscopy. The presence of such low Ti-content in theSnO2 lattice drastically reduces the band gap of these solid solutions,as determined by UV–vis absorption, almost to that of pureTiO2. Furthermore, titania reduces the number of rooted and terminal OH species (that arecorrelated to the cross-sensitivity of tin oxide to water) on the particle surface asdetermined by IR-spectroscopy.The present material represents a new class of sensors where detection of gases and organicvapors can be accomplished without pre-treatment of the gas mixture, avoiding othersemiconducting components that require more heating power and that add bulkiness to asensing device. This is attractive in developing miniaturized sensors especially formicroelectronics and medical diagnostics.

ADVANCES IN F0F1-ATP SYNTHASE BIOLOGICAL PROTEIN NANOMOTOR: FROM MECHANISMS AND STRATEGIES TO POTENTIAL APPLICATIONS

Movement and shape changes are fundamental aspects of all living organisms. This biological motility results from the biological nanomotors, in particular protein nanomotors. Cells contain a variety of protein nanomotors that rotate (e.g., F0F1-ATP synthase or bacterial flagellar motors) or move in a linear fashion (e.g., the kinesin, myosin and dynein motors). F0F1-ATP synthase is one of the ideal nanomotors or energy providing systems for micro/nanomachines because of its small size, smart and perfect structure, and ultra-high energy transfer efficiency. Therefore, in this paper, we have reviewed the structure, mechanism, and potential applications of the F0F1-ATP synthase nanomotor. In all organisms, the F0F1-ATP synthase consists of two distinct nanomotors, F0and F1. The F0moiety is embedded in the membrane and is a detergent soluble unit while the F1moiety protrudes from the membrane and is a water soluble unit. F0F1-ATP synthase operates as two stepper motor/generators coupled by a common shaft and an electrochemical-to-mechanical-to-chemical energy transducer with an astounding 360° rotary motion of subunits. F0F1-ATP synthase nanomotor may enable the creation of a new class of sensors, mechanical force transducers, actuators, and nanomechanical devices. Thus, the F0F1-ATP synthase nanomotor field has expanded into a wide variety of science.

First evidence of phase-contrast imaging with laboratory sources and active pixel sensors

The aim of the present work is to achieve a first step towards combining the advantages of an innovative X-ray imaging technique—phase-contrast imaging (XPCi)—with those of a new class of sensors, i.e. CMOS-based active pixel sensors (APSs). The advantages of XPCi are well known and include increased image quality and detection of details invisible to conventional techniques, with potential application fields encompassing the medical, biological, industrial and security areas. Vanilla, one of the APSs developed by the MI-3 collaboration (see http://mi3.shef.ac.uk), was thoroughly characterised and an appropriate scintillator was selected to provide X-ray sensitivity. During this process, a set of phase-contrast images of different biological samples was acquired by means of the well-established free-space propagation XPCi technique. The obtained results are very encouraging and are in optimum agreement with the predictions of a simulation recently developed by some of the authors thus further supporting its reliability. This paper presents these preliminary results in detail and discusses in brief both the background to this work and its future developments.

Wireless and distributed sensing of the shape of morphing structures

Monitoring the shape of morphing structures is essential for their effective and safe operation. However, current sensing systems such as fiber optic sensors are expensive, brittle, and unsuitable for monitoring large shape changes without being susceptible to failure or performance degradation. Therefore, a new class of sensors that does not suffer from these serious limitations is presented. The sensor system relies in its operation on a specially configured distributed network of wires that is embedded in the composite fabric of these structures. The output of the sensor network is wirelessly transmitted to a control processor to compute the linear and angular deflections, the shape, and maps of the strain distribution over the entire surface of the morphing. The deflection and shape information are vital to ascertain that the structure is properly deployed. The strain map ensures that the structure is not loaded excessively to adversely affecting its service life. The equations governing the operation of the sensor network are developed for a beam-like morphing structure using the non-linear theory of finite elements. The resulting equations will provide the sensor with its unique interpolation capabilities that make it possible to map the linear and angular deflection and strain field distribution over the entire surface of the morphing structure. The theoretical and experimental characteristics of the sensor network are determined under static and dynamic loading conditions. The results obtained are used to demonstrate the merits and potential of this new class of sensors as a viable means for monitoring the deflections of 1D morphing structures. Integration of the proposed sensor network with the supporting electronics and with arrays of flexible actuators will enable the development of a self-contained, actively controlled, and autonomously operating new generation of morphing.

Organic thin-film transistor sensors: Interface dependent and gate bias enhanced responses

Organic thin film transistors are a new class of sensors potentially capable of outperforming chemiresistors. They can be operated at room temperature, offer the advantage of remarkable response repeatability and can function as multi-parameter sensors. In this paper, evidence of OTFT response dependence on important parameters such as the chemical nature of the organic semiconductor active layer and the gate-dielectric/organic-semiconductor interface are produced. A sizable response enhancement of an OTFT sensor operated in the enhancement mode is also presented indicating that an OTFT can in principle lead to a lower detection limit than a resistor-type sensor with the same organic semiconductor.

Parylene micro membrane capacitive sensor array for chemical and biological sensing

The need for high-throughput label-free multiplexed sensors for chemical and biological sensing has increased tremendously in the last decade with new applications in the areas of genetics, diagnostics, drug discovery, as well as security and threat evaluation. Surface stress-based sensors are a relatively new class of sensors that has immense potential to satisfy the demand, and has been investigated extensively in the recent years. In this paper we present the design and fabrication of a novel parylene micro membrane surface stress sensor that exploits the low mechanical stiffness of polymers. The salient features of the sensor are that it: (i) is label-free; (ii) is a universal platform suitable for both chemical and biological sensing; (iii) uses electronic (capacitive detection) readout; (iv) has integrated microfluidics for addressing individual sensors on the chip; (v) is capable of handling both liquid and gas samples; (vi) is made using standard low temperature microfabrication processes (<120°C); (vii) can readily be scaled and multiplexed. The first generation sensor arrays were fabricated and the sensor response to organic vapors like isopropyl alcohol and toluene were measured.

Organic Thin-Film Transistor Sensors: Interface Dependent and Gate Bias Enhanced Responses

AbstractOrganic Thin Film Transistors are a new class of sensors potentially capable of outperforming chemiresistors. They can be operated at room temperature, offer the advantage of remarkable response repeatability and can function as multi-parameter sensors. In this paper evidence of OTFT response dependence on important parameters such as the chemical nature of the organic semiconductor active layer and the gate-dielectric/organic-semiconductor interface are produced. A sizable response enhancement of an OTFT sensor operated in the enhancement mode is also presented indicating that an OTFT can in principle lead to a lower detection limit than a resistor-type sensor with the same organic semiconductor.

Sequence specific fluorescence detection of double strand DNA.

Methods for the fluorescent detection of specific sequences of double strand DNA in homogeneous solution may be useful in the field of human genetics. A series of hairpin polyamides with tetramethyl rhodamine (TMR) attached to an internal pyrrole ring were synthesized, and the fluorescence properties of the polyamide-fluorophore conjugates in the presence and absence of duplex DNA were examined. We observe weak TMR fluorescence in the absence of DNA. Addition of >/=1:1 match DNA affords a significant fluorescence increase over equimolar mismatch DNA for each polyamide-TMR conjugate. Polyamide-fluorophore conjugates offer a new class of sensors for the detection of specific DNA sequences without the need for denaturation. The polyamide-dye fluorescence-based method can be used to screen in parallel the interactions between aromatic ring pairs and the minor groove of DNA even when the binding site contains a non-Watson-Crick DNA base pair. A ranking of the specificity of three polyamide ring pairs-Py/Py, Im/Py, and Im/Im-was established for all 16 possible base pairs of A, T, G, and C in the minor groove. We find that Im/Im is an energetically favorable ring pair for minor groove recognition of the T.G base pair.

Targeted origin placementfor the autonomous gain-phase tailoring of piezoelectricsensors

Targeted origin placement can be shown to complimentmathematical tools such as the image method, windowfunctions and two-sided Laplace transformation for designing awhole new class of piezoelectric sensors that can be used totailor the gain and phase portions of the sensor transfer functions independently. It can be demonstrated that by properlyapplying the boundary conditions and the method of imaging, thetargeted origin of this new class of sensor design can betraversed anywhere along the surface of the testing structure.In addition, the active sensor concept that integratesclassical control theory with piezoelectric sensors can be adapted to further advance sensor technology. The designconcept, theoretical derivations, numerical calculations andexperimental verifications of implementing this class of newsensor design to influence flexible structure control and pointsensor design methodologies are detailed.

Nanobiosensors: probing the sanctuary of individual living cells.

Recently, nanotechnology has been revolutionizing important areas in molecular biology, especially diagnostics and therapy at the molecular and cellular level. The combination of nanotechnology, biology, and photonics opens the possibility of detecting and manipulating atoms and molecules using nanodevices, which have the potential for a wide variety of medical uses at the cellular level. The nanoprobes were fabricated with optical fibers pulled down to tips with distal ends having sizes of approximately 30-50 nm. The nanoscale size of this new class of sensors, allows for measurements in the smallest of environments. One such environment that has evoked a great deal of interest is that of individual cells. Using these nanobiosensors, it has become possible to probe individual chemical species in specific locations throughout a cell. This article provides an overview of the principle, development, and applications of optical nanosensor systems for in vivo bioanalysis at the single-cell level. The fiberoptics nanoprobes were covalently bound with antibodies that are selective to target analyte molecules. Excitation light is launched into the fiber and the resulting evanescent field at the tip of the fiber is used to excite target molecules bound to the antibody molecules. The fluorescence emission from the analyte molecules is then collected via a microscope. The usefulness and potential of this nanotechnology-based biosensor systems in biological research and applications in single-cell analysis are discussed.

Nonlinear Dynamics Sensitivity Analysis in Networks and Applications to Sensing

We present an extended framework and software tools for the analysis of the non-linear dynamical (chaotic) processes in networks of identical systems and in hybrid networks. The systems are characterized by several external and internal parameters, and the evolution of the dynamics in the multidimensional space of the parameters is investigated. Extensions of the bifurcation diagram are introduced as theoretical tools, and related software tools to analyze the patterns in the parametric space are presented. Based on this analysis, the development of a new class of sensors, relaying on chaotic processes, with capabilities of data fusing and pattern recognition is presented. Several applications are discussed. Experimental results with circuits implementing several applications are also presented and discussed

New sensors based on the magnetoelastic resonance of metallic glasses

High magnetostriction Fe-rich metallic glasses in the form of ribbons show a magnetoelastic resonance characterized by the frequency of the longitudinal vibrational mode of the sample, ω r, at which the magnetic susceptibility χ shows a sharp maximum. In this work we propose to use the sensibility of ω r and χ to the external (bias) field in order to design a new class of sensors. Measurements were performed using two different configurations for detecting the magnetoelastic resonance: first, a typical set-up with two different coaxial coils to apply the excitation field and to pick up the signal, respectively. Secondly, with a more simplified set-up consisting only in a small excitation-detection coil. In both experiments the influence of applying an inhomogeneous bias field, provided by a small permanent magnet, has been tested. Results from these features are discussed.