28 research outputs found
Interface Circuits for Microsensor Integrated Systems
ca. 200 words; this text will present the book in all promotional forms (e.g. flyers). Please describe the book in straightforward and consumer-friendly terms. [Recent advances in sensing technologies, especially those for Microsensor Integrated Systems, have led to several new commercial applications. Among these, low voltage and low power circuit architectures have gained growing attention, being suitable for portable long battery life devices. The aim is to improve the performances of actual interface circuits and systems, both in terms of voltage mode and current mode, in order to overcome the potential problems due to technology scaling and different technology integrations. Related problems, especially those concerning parasitics, lead to a severe interface design attention, especially concerning the analog front-end and novel and smart architecture must be explored and tested, both at simulation and prototype level. Moreover, the growing demand for autonomous systems gets even harder the interface design due to the need of energy-aware cost-effective circuit interfaces integrating, where possible, energy harvesting solutions. The objective of this Special Issue is to explore the potential solutions to overcome actual limitations in sensor interface circuits and systems, especially those for low voltage and low power Microsensor Integrated Systems. The present Special Issue aims to present and highlight the advances and the latest novel and emergent results on this topic, showing best practices, implementations and applications. The Guest Editors invite to submit original research contributions dealing with sensor interfacing related to this specific topic. Additionally, application oriented and review papers are encouraged.
Strategies for the Accurate Measurement of the Resonance Frequency in QCM-D Systems via Low-Cost Digital Techniques
In this paper, an FPGA (Field Programmable Gate Array)-based digital architecture for the measurement of quartz crystal microbalance (QCM) oscillating frequency of transient responses, i.e., in QCM-D (QCM and Dissipation) applications, is presented. The measurement system is conceived for operations in liquid, with short QCM transient responses due to the large mechanical load. The proposed solution allows for avoiding the complex processing systems typically required by the QCM-D techniques and grants frequency resolutions better than 1 ppm. The core of the architecture is a reciprocal digital frequency meter, combined with the preprocessing of the QCM signal through mixing operations, such as a step-down of the input frequency and reducing the measurement error. The measurement error is further reduced through averaging. Different strategies are proposed to implement the proposed measurement solution, comprising an all-digital circuit and mixed analog/digital ones. The performance of the proposed architectures is theoretically derived, compared, and analyzed by means of experimental data obtained considering 10 MHz QCMs and 200 μs long transient responses. A frequency resolution of about 240 ppb, which corresponds to a Sauerbrey mass resolution of 8 ng/cm2, is obtained for the all-digital solution, whereas for the mixed solution the resolution halves to 120 ppb, with a measurement time of about one second over 100 repetitions
Characterization of the Elastic, Piezoelectric, and Dielectric Properties of Langatate At High Temperatures Up To 900 ◦C
The acoustic wave constants of the piezoelectric crystal langatate (LGT, La3Ga5.5Ta0.5O14) are characterized up to 900 ◦C for the first time in this work, targeting the development of high-temperature acoustic wave (AW) devices. There is a pressing need for sensors and frequency control systems that operate at high temperature, above 200 ◦C, and in harsh environments, with applications found in the industrial process control, automotive, aerospace, and power generation industries and in gas and petroleum exploration. Surface acoustic wave (SAW) and bulk acoustic wave (BAW) devices, using piezoelectric crystals such as LGT, have the capability to provide the desired high-temperature sensors for temperature, pressure, strain, and gas species measurement. Langatate, a member of the langasite crystal family, retains crystal structure up to the melting point at 1470 ◦C and has higher piezoelectric coupling than quartz and langasite; however, a full set of LGT AW constants required for SAW and BAW device design had not previously been characterized above 150 ◦C.
In this work, the LGT elastic, piezoelectric, and dielectric constants have been extracted up to 900 ◦C, providing a complete set of AW constants. The LGT elastic and piezoelectric constants were measured using resonant ultrasound spectroscopy (RUS) and determined by fitting predicted resonance modes with measured spectra of LGT samples heated in a custom-fabricated high-temperature furnace. The LGT dielectric permittivity and conductivity constants were extracted from parallel-plate capacitor measurements. Langatate SAW devices were fabricated and the measured properties up to 900 ◦C were found to be in very good agreement with the predictions, thus validating the extracted LGT high-temperature constants.
The newly determined LGT constants were used to locate SAW orientations for high-temperature operation by calculating the SAW velocity and temperature coefficient of delay (TCD) up to 900 ◦C along multiple regions in space. Multiple SAW orientations were identified with potentially desirable properties such as turnover temperatures, TCD=0, at elevated temperatures up to 500 ◦C, and either low or high sensitivity to temperature. Differential high-temperature sensors utilizing a suite of SAW sensors on the same wafer were proposed and experimentally demonstrated. Additionally, BAW orientations were identified with turnover temperatures ranging from 100 ◦C to 550 ◦C
Implementing Diode-Pumped Solid-State Lasers into Instrumental Analytics
Eine der bedeutendsten technischen Errungenschaften des letzten Jahrhunderts beinhaltet
zweifelsfrei die Erfindung des Lasers. Bereits wenige Jahrzehnte nach seiner ersten technischen Umsetzung ist er heute aus so unterschiedlichen Anwendungsbereichen wie der
Mess- und Regeltechnik, der Unterhaltungselektronik, sowie der industriellen Fertigung
und Materialbearbeitung nicht mehr wegzudenken. Die analytische Chemie bildet hier
keine Ausnahme. Die Möglichkeit mittels Laserstrahlung sowohl räumlich als auch zeitlich
definiert einen maßgeschneiderten Energieeintrag in Materialsysteme vorzunehmen, wird
heute umfangreich in diversen Analyseverfahren eingesetzt. Ein Meilenstein auf dem Gebiet
der Laserentwicklung stellt die Einführung diodengepumpter Festkörperlaser (DPSS)
dar. Diese neuartige Lasergeneration vereint die Vorteile einer begünstigten Energiebilanz
durch resonante Anregung im Lasermedium mit einer erhöhten Flexibilität der zeitlichen
Modulation der Laserausgangsleistung. Während DPSS Laser auf dem Gebiet der Materialbearbeitung bereits die Hälfte des Marktanteils ausmachen, finden sie bislang in den
analytischen Wissenschaften nur wenig Verbreitung. Auch hier könnten die inhärenten
Vorteile von DPSS Lasern bezüglich Konversionseffizienz, Stabilität, Flexibilität und Strahlprofil maßgeblich zu einer Optimierung relevanter Teilschritte beitragen. Die vorliegende Arbeit schließt diese Lücke, indem sie die Anwendbarkeit eines modernen DPSS Lasers für solch unterschiedliche Aufgaben wie der Laserablation, der Raman-Spektroskopie, der atomaren und molekularen Emissionsspektroskopie, bis hin zur Erzeugung eines neuartigen quasi-kontinuierlichen, luftgetragenen Plasmas für die Atmosphärendruck-Ionisation untersucht. In allen Studien konnten die Verbesserungen der jeweiligen analytischen Verfahren auf die Eigenschaften des verwendeten Lasers zurückgeführt werden.Without any doubt, one of the most momentous technical achievements of the last century
has been the invention of the laser. Today, merely some decades after its first technical
realization, the laser has established a leading role in such broad application fields as
sensing and control engineering, consumer electronics, as well as industrial production
and materials processing. Analytical chemistry does not make an exception. The possibility
of both spatially and temporally well-confined introduction of precisely dosed and
defined energy into any material is nowadays widely exploited in a plethora of analytical
techniques. A milestone in the field of laser technology was the advent of diode-pumped
solid-state (DPSS) lasers. This new generation of laser systems combines the benefits of an
advantageous energy balance, caused by resonant excitation of the laser medium, with an
enhancement in flexibility in terms of modulation of the laser output. While DPSS lasers
already account for half of the devices used in materials processing, the dissemination
in the analytical sciences has so far hardly occurred. Also here, the inherent advantages
of DPSS lasers regarding efficiency, reliability, flexibility, and beam profile could greatly
contribute in a multitude of analytically relevant sub-steps. This thesis closes this gap by
studying the applicability of a current state-of-the-art DPSS laser for as different tasks as
laser ablation, Raman spectroscopy, atomic and molecular emission spectroscopy, all the
way to generating a generally new quasi-continuous airborne plasma for ambient ionization.
In all cases studied, the improvement of the respective analytical techniques could
be ascribed to the intrinsic properties of the used laser
Applications of Antenna Technology in Sensors
During the past few decades, information technologies have been evolving at a tremendous rate, causing profound changes to our world and to our ways of living. Emerging applications have opened u[ new routes and set new trends for antenna sensors. With the advent of the Internet of Things (IoT), the adaptation of antenna technologies for sensor and sensing applications has become more important. Now, the antennas must be reconfigurable, flexible, low profile, and low-cost, for applications from airborne and vehicles, to machine-to-machine, IoT, 5G, etc. This reprint aims to introduce and treat a series of advanced and emerging topics in the field of antenna sensors
Design, manufacturing and characterisation of a wireless flexible pressure sensor system for the monitoring of the gastro-intestinal tract
Ingestible motility capsule (IMC) endoscopy holds a strong potential in providing
advanced diagnostic capabilities within the small intestine with higher patient tolerance
for pathologies such as irritable bowel syndrome, gastroparesis and chronic abdominal
amongst others. Currently state-of-the art IMCs are limited by the use of obstructive off-the-shelf sensing modules that are unable to provide multi-site tactile monitoring of the
Gastro-Intestinal tract.
In this work a novel 12 mm in diameter by 30 mm in length IMC is presented that utilises
custom-built flexible, thin-film, biocompatible, wireless and highly sensitive tactile
pressure sensors arrays functionalising the capsule shell. The 150 μm thick,
microstructured, PDMS flexible passive pressure sensors are wirelessly powered and
interrogated, and are capable of detecting pressure values ranging from 0.1 kPa up to 30
kPa with a 0.1 kPa resolution. A novel bottom-up wafer-scale microfabrication process
is presented which enables the development of these ultra-dense, self-aligned, scalable
and uniquely addressable flexible wireless sensors with high yield (>80%). This thesis
also presents an innovative metallisation microfabrication process on soft-elastomeric
substrates capable to withstand without failure of the tracks 180o
bending, folding and
iterative deformation such as to allow conformable mapping of these sensors. A custom-built and low-cost reflectometer system was also designed, built and tested within the
capsule that can provide a fast (100 ms) and accurate extraction (±0.1 kPa) of their
response. In vitro and in vivo characterisation of the developed IMC device is also
presented, facilitated respectively via the use of a biomimetic phantom gut and via live
porcine subjects. The capsule device was found to successfully capture respiration, low-amplitude and peristaltic motility of the GI tract from multiple sites of the capsule.UK Engineering & Physical Sciences Research Council (EPSRC) through the Programme Grant Sonopill
(EP/K034537/2)James Watt Scholarshi
Femtosecond laser microfabricated devices for biophotonic applications
Femtosecond Laser DirectWriting has emerged as a key enabling technology
for realising miniaturised biophotonic applications offering clear advantages
over competing soft-lithography, ion-exchange and sol-gel based fabrication
techniques. Waveguide writing and selective etching with three-dimensional
design flexibility allows the development of innovative and unprecedented
optofluidic architectures using this technology. The work embodied in this
thesis focuses on utilising the advantages offered by direct laser writing in
fabricating integrated miniaturised devices tailored for biological analysis.
The first application presented customised the selective etching phenomenon
in fused silica by tailoring the femtosecond pulse properties during the writing
process. A device with an embedded network of microchannels with a
significant difference in aspect-ratio was fabricated, which was subsequently
applied in achieving the high-throughput label-free sorting of mammalian
cells based on cytoskeletal deformability. Analysis on the device output cell
population revealed minimal effect of the device on cell viability.
The second application incorporated an embedded microchannel in fused
silica with a monolithically integrated near-infrared optical waveguide. This
optofluidic device implemented the thermally sensitive emission spectrum
of semiconductor nanocrystals in undertaking remote thermometry of the
localised microchannel environment illuminated by the waveguide. Aspects
relating to changing the wavelength of illumination from the waveguide were
analysed. The effect of incorporating carbon nanotubes as efficient heaters
within the microchannel was investigated. Spatio-thermal imaging of the
microchannel illuminated by the waveguide revealed the thermal effects to
extend over distances appreciably longer than the waveguide cross-section.
On the material side of direct laser writing, ultra-high selective etching is
demonstrated in the well-known laser crystal Nd:YAG. This work presents
Nd:YAG as a material with the potential to develop next-generation optofluidic
devices
1-D broadside-radiating leaky-wave antenna based on a numerically synthesized impedance surface
A newly-developed deterministic numerical technique for the automated design of metasurface antennas is applied here for the first time to the design of a 1-D printed Leaky-Wave Antenna (LWA) for broadside radiation. The surface impedance synthesis process does not require any a priori knowledge on the impedance pattern, and starts from a mask constraint on the desired far-field and practical bounds on the unit cell impedance values. The designed reactance surface for broadside radiation exhibits a non conventional patterning; this highlights the merit of using an automated design process for a design well known to be challenging for analytical methods. The antenna is physically implemented with an array of metal strips with varying gap widths and simulation results show very good agreement with the predicted performance
Beam scanning by liquid-crystal biasing in a modified SIW structure
A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium