7,421 research outputs found
Developments in nanoparticles for use in biosensors to assess food safety and quality
The following will provide an overview on how advances in nanoparticle technology have contributed towards developing biosensors to screen for safety and quality markers associated with foods. The novel properties of nanoparticles will be described and how such characteristics have been exploited in sensor design will be provided. All the biosensor formats were initially developed for the health care sector to meet the demand for point-of-care diagnostics. As a consequence, research has been directed towards miniaturization thereby reducing the sample volume to nanolitres. However, the needs of the food sector are very different which may ultimately limit commercial application of nanoparticle based nanosensors. © 2014 Elsevier Ltd
Fiber-optic and coaxial-cable extrinsic Fabry-Perot interferometers for sensing applications
”The fiber-optic extrinsic Fabry-Perot interferometer (EFPI) is one of the simplest sensing configurations and is widely used in various applications due to its prominent features, such as high sensitivity, immunity to electromagnetic interference, and remote operation capability. In this research, a novel one-dimensional wide-range displacement sensor and a three-dimensional displacement sensor based on fiber-optic EFPIs are demonstrated. These two robust and easy-to-manufacture sensors expand the application scope of the fiber-optic EFPI sensor devices, and have great potential in structural health monitoring, the construction industry, oil well monitoring, and geo-technology.
Furthermore, inspired by the fiber-optic EFPI, a novel and universal ultra-sensitive microwave sensing platform based on an open-ended hollow coaxial cable resonator (OE-HCCR, i.e., the coaxial cable EFPI) is developed. Both the theoretical predictions and experimental results demonstrate the ultra-high sensitivity of the OE-HCCR device to variations of the gap distance between the endface of the coaxial cable and an external metal plate. Additionally, combining the chemical-specific adsorption properties of metal-organic framework (MOF) materials with the dielectric sensitivity of the OE-HCCR, a mechanically robust and portable gas sensor device (OE-HCCR-MOF) with high chemical selectivity and sensitivity is proposed and experimentally demonstrated. Due to its low cost, high sensitivity, all-metal structure, robustness, and ease of signal demodulation, it is envisioned that the proposed OE-HCCR device will advance EFPI sensing technologies, revolutionize the sensing field, and enable many important sensing applications that take place in harsh environments”--Abstract, page iv
Nanoantennas for visible and infrared radiation
Nanoantennas for visible and infrared radiation can strongly enhance the
interaction of light with nanoscale matter by their ability to efficiently link
propagating and spatially localized optical fields. This ability unlocks an
enormous potential for applications ranging from nanoscale optical microscopy
and spectroscopy over solar energy conversion, integrated optical
nanocircuitry, opto-electronics and density-ofstates engineering to
ultra-sensing as well as enhancement of optical nonlinearities. Here we review
the current understanding of optical antennas based on the background of both
well-developed radiowave antenna engineering and the emerging field of
plasmonics. In particular, we address the plasmonic behavior that emerges due
to the very high optical frequencies involved and the limitations in the choice
of antenna materials and geometrical parameters imposed by nanofabrication.
Finally, we give a brief account of the current status of the field and the
major established and emerging lines of investigation in this vivid area of
research.Comment: Review article with 76 pages, 21 figure
Detecting Superlight Dark Matter with Fermi-Degenerate Materials
We examine in greater detail the recent proposal of using superconductors for
detecting dark matter as light as the warm dark matter limit of O(keV).
Detection of such light dark matter is possible if the entire kinetic energy of
the dark matter is extracted in the scattering, and if the experiment is
sensitive to O(meV) energy depositions. This is the case for Fermi-degenerate
materials in which the Fermi velocity exceeds the dark matter velocity
dispersion in the Milky Way of ~10^-3. We focus on a concrete experimental
proposal using a superconducting target with a transition edge sensor in order
to detect the small energy deposits from the dark matter scatterings.
Considering a wide variety of constraints, from dark matter self-interactions
to the cosmic microwave background, we show that models consistent with
cosmological/astrophysical and terrestrial constraints are observable with such
detectors. A wider range of viable models with dark matter mass below an MeV is
available if dark matter or mediator properties (such as couplings or masses)
differ at BBN epoch or in stellar interiors from those in superconductors. We
also show that metal targets pay a strong in-medium suppression for kinetically
mixed mediators; this suppression is alleviated with insulating targets.Comment: 40 pages, 10 figures; v2: updated figures, matches published versio
Optical Fibre Sensors Using Graphene-Based Materials: A Review
Graphene and its derivatives have become the most explored materials since Novoselov and Geim (Nobel Prize winners for Physics in 2010) achieved its isolation in 2004. The exceptional properties of graphene have attracted the attention of the scientific community from different research fields, generating high impact not only in scientific journals, but also in general-interest newspapers. Optical fibre sensing is one of the many fields that can benefit from the use of these new materials, combining the amazing morphological, chemical, optical and electrical features of graphene with the advantages that optical fibre offers over other sensing strategies. In this document, a review of the current state of the art for optical fibre sensors based on graphene materials is presented
The trade-off characteristics of acoustic and pressure sensors for the NASP
Results of a trade study for the development of pressure and acoustic sensors for use on the National Aerospace Plane (NASP) are summarized. Pressure sensors are needed to operate to 100 psia; acoustic sensors are needed that can give meaningful information about a 200 dB sound pressure level (SPL) environment. Both sensors will have to operate from a high temperature of 2000 F down to absolute zero. The main conclusions of the study are the following: (1) Diaphragm materials limit minimum size and maximum frequency response attainable. (2) No transduction is available to meet all the NASP requirements with existing technology. (3) Capacitive sensors are large relative to the requirement, have limited resolution and frequency response due to noise, and cable length is limited to approximately 20 feet. (4) Eddy current sensors are large relative to the requirement and have limited cable lengths. (5) Fiber optic sensors provide the possibility for a small sensor, even though present developments do not exhibit that characteristic. The need to use sapphire at high temperature complicates the design. Present high temperature research sensors suffer from poor resolution. A significant development effort will be required to realize the potential of fiber optics. (6) Short-term development seems to favor eddy current techniques with the penalty of larger size and reduced dynamic range for acoustic sensors. (7) Long-term development may favor fiber optics with the penalties of cost, schedule, and uncertainty
Wireless, Customizable Coaxially-shielded Coils for Magnetic Resonance Imaging
Anatomy-specific RF receive coil arrays routinely adopted in magnetic
resonance imaging (MRI) for signal acquisition, are commonly burdened by their
bulky, fixed, and rigid configurations, which may impose patient discomfort,
bothersome positioning, and suboptimal sensitivity in certain situations.
Herein, leveraging coaxial cables' inherent flexibility and electric field
confining property, for the first time, we present wireless, ultra-lightweight,
coaxially-shielded MRI coils achieving a signal-to-noise ratio (SNR) comparable
to or surpassing that of commercially available cutting-edge receive coil
arrays with the potential for improved patient comfort, ease of implementation,
and significantly reduced costs. The proposed coils demonstrate versatility by
functioning both independently in form-fitting configurations, closely adapting
to relatively small anatomical sites, and collectively by inductively coupling
together as metamaterials, allowing for extension of the field-of-view of their
coverage to encompass larger anatomical regions without compromising coil
sensitivity. The wireless, coaxially-shielded MRI coils reported herein pave
the way toward next generation MRI coils
Spin Manipulation of the Nitrogen Vacancy Center and its Applications
Das Stickstoff-Fehlstellen-Zentrum (NV-Zentrum) in Diamant ist eines der vielver-
sprechendsten Spinsysteme für Anwendungen im Bereich Quanten-Computing,
-Information und -Sensorik. Die Abhängigkeit der Fluoreszenzintensität vom Spinzu-
stand ermöglicht dabei das rein optische Auslesen des Spinzustandes. Für alle
Anwendungen, die auf aktive Spinmanipulation angewiesen sind, ist Mikrowellen-
strahlung unverzichtbar. Die Fähigkeit, den Spinzustand von NV-Zentren vollständig
zu kontrollieren, wird durch die Richtung, Intensität und Polarisation der Mikrow-
ellenstrahlung definiert. Es gibt verschiedene Ansätze, um geeignete Mikrowellen-
strahlung zu erzeugen, aber oft ist die Feldintensität zu gering oder es gibt andere
Einschränkungen, z.B. eine geringe Frequenzbandbreite.
Im ersten Teil meiner Arbeit untersuche ich transparente Leiter auf Basis von Indium-
Zinn-Oxid (ITO), um die Mikrowellenansteuerung von NV-Zentren zu optimieren.
Dabei wird eine detaillierte Analyse von ITO auf Diamant bezüglich einzelner
NV-Zentren vorgestellt. Ein mathematisches Modell wurde entwickelt, um die
Feldverteilung vorherzusagen. Zusätzlich wird eine Methode zur Kontrolle der
Mikrowellenpolarisation mit einer transparenten ITO-Struktur vorgestellt, die zu
einer vollständigen Kontrolle des Spinzustands des NV-Zentrums führt. Weiterhin
werden Simulationen in Kombination mit einem analytischen Modell verwendet, um
optimale Mikrowellenparameter für die Spinkontrolle vorherzusagen.
Für eine kommerzielle Anwendung von NV-Zentren als Magnetfeldsensor sind Pro-
duktionskosten und Bauteilkomplexität wichtige Faktoren, die in der Forschung
oft vernachlässigt werden. Der zweite Teil meiner Arbeit konzentriert sich da-
her auf einen mikrowellenfreien Ansatz zur Magnetometrie mit NV-Zentren. Der
Einfluss der Laseranregung auf den magnetischen Kontrast wird an einzelnen NV-
Zentren, Ensembles von NV-Zentren und Nano-Diamantpulver mit einer hohen NV-
Zentrenkonzentration dargestellt und nachfolgend zur Demonstration von isotropen
Magnetfeldmessung verwendet. Abschließend wird die Anwendbarkeit durch die
Konstruktion eines Magnetfeldsensors aus Komponenten der Automobilbranche
gezeigt.The nitrogen vacancy center (NV center) in diamond is one of the most promising
spin systems for applications in quantum computing, information and sensing. The
dependency of the fluorescence intensity on the spin state allows a purely optical
readout of the spin state. A green laser can be used to pump the NV center in the
spin ground state while microwave radiation can manipulate the spin state of the
NV center. For all applications depending on active spin manipulation, microwave
radiation is indispensable. The ability to fully control the spin state of NV centers is
defined by direction, strength and polarization of the microwave radiation. Different
approaches exist to deliver the microwave radiation, but they often lack in strength
or have other restrictions, e.g. a small frequency band width.
In the first part of my thesis, I investigate transparent conductors based on indium
tin oxide (ITO) to optimize microwave delivery. In this process a detailed analysis
of ITO on diamond concerning confocal microscopy through this transparent film
is presented. A mathematical model was developed and tested to predict the field
distribution in possible applications. Additionally a method to control microwave
polarization with a transparent ITO structure is shown which results in full spin
state control of the NV center. Furthermore simulations combined with a analytical
model are used to predict optimal microwave parameters for spin control.
For a commercial application of NV centers as a magnetic field sensor, important
factors are production cost and device complexity which are often neglected in
research. The second part of my thesis therefore focuses on a microwave free
approach of NV center magnetometry for industry applications. The influence of
laser excitation on magnetic contrast was studied on single NV centers, ensembles
of NV centers and nano diamond powder with a high NV center concentration. The
findings were used to demonstrate isotropic magnetic field sensing. Finally, the
applicability was shown by constructing a magnetic field sensor from automotive
grade components
Biosensors for cardiac biomarkers detection: a review
The cardiovascular disease (CVD) is considered as a major threat to global health. Therefore, there is a growing demand for a range of portable, rapid and low cost biosensing devices for the detection of CVD. Biosensors can play an important role in the early diagnosis of CVD without having to rely on hospital visits where expensive and time-consuming laboratory tests are recommended. Over the last decade, many biosensors have been developed to detect a wide range of cardiac marker to reduce the costs for healthcare. One of the major challenges is to find a way of predicting the risk that an individual can suffer from CVD. There has been considerable interest in finding diagnostic and prognostic biomarkers that can be detected in blood and predict CVD risk. Of these, C-reactive protein (CRP) is the best known biomarker followed by cardiac troponin I or T (cTnI/T), myoglobin, lipoprotein-associated phospholipase A(2), interlukin-6 (IL-6), interlukin-1 (IL-1), low-density lipoprotein (LDL), myeloperoxidase (MPO) and tumor necrosis factor alpha (TNF-α) has been used to predict cardiovascular events. This review provides an overview of the available biosensor platforms for the detection of various CVD markers and considerations of future prospects for the technology are addressed
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