35 research outputs found
Multi-component strain development in superconducting magnet coils monitored using fibre Bragg grating sensors fabricated in highly linearly birefringent fibre
No full textThe commissioning of superconducting magnet coils was monitored using embedded optical fibre Bragg grating sensors (FBG) fabricated in highly linearly birefringent (HiBi) fibre. The HiBi FBG sensors monitored the internal strain developed in the coils during the energization of the coils. The development of multiple components of strain in the coils when the magnet was energized and quenched was monitored, revealing phenomena that it had not been previously possible to measure using other sensor technologies
Quench characteristics of a stabilizer-free 2G HTS conductor
No full textThe prospect of medium/high field superconducting magnets using second generation (2G) HTS tapes is approaching reality with continued enhancement in the performance of these conductors. While the cryogenic stability and quench propagation are fundamental issues for the design and safe operation of superconducting magnets, there is insufficient understanding and experimental data for 2G HTS conductors, in particular for the high field scenario at low temperature (<77 K) where the current sharing regime is much larger than in low temperature superconductors. The present work includes a systematic characterization of the relevant thermal-electrical properties used for both qualitative discussion and numerical analysis. Direct measurements of one dimensional adiabatic quench initiation and propagation of a stabilizer-free 2G conductor have been carried out with spatial-temporal recording of temperature and voltage following the deposition of varying local heat pulses to the conductor at different temperatures between 30 K and 77 K carrying different transport currents. The minimum quench energy, and the heat generation in the minimum propagation zone (MPZ) have been obtained as a function of temperature and transport current. The results show quench features unique to HTS such as an increasing MPZ with transport current and higher quench energies at lower temperatures. The experimental results are discussed in the context of current sharing over a large temperature range
Development of superconducting bolometer device technology for millimeter-wave cosmology instruments
No full textThe Cold-Electron Bolometer (CEB) is a sensitive detector of millimeter-wave radiation, in which tunnel junctions are used as temperature sensors of a nanoscale normal metal strip absorber. The absorber is fed by an antenna via two Superconductor-Insulator-Normal metal (SIN) tunnel junctions, fabricated at both ends of the absorber. Incoming photons excite electrons, heating the whole electron system. The incoming RF power is determined by measuring the tunneling current through the SIN junctions. Since electrons at highest energy levels escape the absorber through the tunnel junctions, it causes cooling of the absorber. This electron cooling provides electro-thermal feedback that makes the saturation power of a CEB well above that of other types of millimeter-wave receivers. The key features of CEB detectors are high sensitivity, large dynamic range, fast response, easy integration in arrays on planar substrates, and simple readout. The high dynamic range allows the detector to operate under relatively high background levels. In this thesis, we present the development and successful operation of CEB, focusing on the fabrication technology and different implementations of the CEB for efficient detection of electromagnetic signals. We present the CEB detector integrated across a unilateral finline deposited on a planar substrate. We have measured the finline-integrated CEB performance at 280-315 mK using a calibrated black-body source mounted inside the cryostat. The results have demonstrated strong response to the incoming RF power and reasonable sensitivity. We also present CEB devices fabricated with advanced technologies and integrated in log-periodic, double-dipole and cross-slot antennas. The measured CEB performance satisfied the requirements of the balloon-borne experiment BOOMERANG and could be considered for future balloon-borne and ground-based instruments. In this thesis we also investigated a planar phase switch integrated in a back-to-back finline for modulating the polarization of weak electromagnetic signals. We examine the switching characteristics and demonstrate that the switching speed of the device is well above the speed required for phase modulation in astronomical instruments. We also investigated the combination of a detector and a superconducting phase switch for modulating the polarization of electromagnetic radiation
Structural friction anisotropy on the nanometer scale
No full textThe ability to understand and control friction on an atomic scale is becoming increasingly important, not only considering the increasingly small scale of mechanical systems that are being developed, but also in respect of furthering the fundamental understanding of friction.
In this thesis, the friction anisotropy at the atomic level was investigated.
This investigation demanded special requirements from the experimental setup, and accordingly, in section 2, a detailed description of a newly developed scanning probe microscope incorporating new electronics and a significantly developed ultra-high vacuum system is given.
In particular, with this newly developed microscope, it is possible to use a specially designed sample holder which rotates the sample in situ, enabling the measurement of friction forces along arbitrary directions of the sample surface.
Measurements on NaCl(100), a well known surface in the field of nanotribology, were compared with Prandtl-Tomlinson simulations. Beside the anisotropy investigations, some newly discovered features along the [100] and [110] directions are presented. Three main conclusions can be drawn from these results: the tip path is influencing the average friction force, friction is reduced by 27\% on one ionic species (whether it is Na or Cl is depending on the tip), and the tip asymmetry is leading to a shift of forward and backward friction force maps along the slow scan direction.
In previous studies, the tip-sample interaction in the Prandtl-Tomlinson model was well described by a sinusoidal potential. This potential, however, fails to sufficiently describe the present results. New simulations were conducted and are presented, which are based on an ab initio calculated potential using density functional theory, and reproduce the main features of the experimental results well.
Investigations on the organic surface of a benzylammonium crystal have shown that the molecular orientation is influencing friction and producing a friction contrast on a molecular scale. While the experimental results clearly show that the corrugation potential is influenced by the molecular orientation, adequate simulations reproducing this phenomena require a potential which includes the relaxation of the surface and tip in contact.
In addition, anisotropy measurements show a strong increase of friction along the [100] orientation.
Friction measurements on patterned pristine and hydrogenated graphene initially revealed a contrast between these two surfaces which are initially covered by a contamination layer. In the course of continuous scanning, a mechanical cleaning occurs. The stability of the contamination layer under mechanical treatment is related to the extent of hydrogenation of the subjacent graphene, the hydrogenated regions require a more intense treatment for cleaning.
It is found that on the cleaned surface, friction reduces to approximately a quarter of its value, and, after this mechanical treatment, the friction contrast between graphene and hydrogenated graphene completely disappears.
It is concluded therefore that despite the strong effect of the hydrogenation to the electronic properties of graphene, it is not degrading its properties as a lubricant
Epidermal radio frequency electronics for wireless power transfer
No full textEpidermal electronic systems feature physical properties that approximate those of the skin, to enable intimate, long-lived skin interfaces for physiological measurements, human–machine interfaces and other applications that cannot be addressed by wearable hardware that is commercially available today. A primary challenge is power supply; the physical bulk, large mass and high mechanical modulus associated with conventional battery technologies can hinder efforts to achieve epidermal characteristics, and near-field power transfer schemes offer only a limited operating distance. Here we introduce an epidermal, far-field radio frequency (RF) power harvester built using a modularized collection of ultrathin antennas, rectifiers and voltage doublers. These components, separately fabricated and tested, can be integrated together via methods involving soft contact lamination. Systematic studies of the individual components and the overall performance in various dielectric environments highlight the key operational features of these systems and strategies for their optimization. The results suggest robust capabilities for battery-free RF power, with relevance to many emerging epidermal technologies. © The Author(s) 2016.TRUEsciescopu
Dataset for "Optimisation of processing conditions during CVD growth of 2D WS2 films from a chloride precursor"
No full textThe dataset represents the results of a CVD growth study of monolayer WS2 films on sapphire substrates and underpins the figures in the main manuscript of "Optimisation of processing conditions during CVD growth of 2D WS2 films from a chloride precursor" that has appeared in the Journal of Materials Science. The manuscript describes an annealing protocol that was developed for the Oxford Instruments Nanofab cold wall CVD reactor to optimise the optical properties of the films. The improvement in quality is demonstrated through a systematic analysis of Raman and photoluminescence spectra and line shapes, including 2D maps generated across large area samples. Atomic force microscopy is used to confirm that the films are indeed uniform single monolayers. Finally, a wet transfer process from sapphire to Si/SiO2 substrates is used to demonstrate that the quality of the films remains unaffected
Accessing the quantum world through electronic transport in carbon nanotubes
No full textIn this thesis we will focus on
(a) superconducting electrodes attached to carbon nanotube quantum dots in
order to study the effects of superconducting correlations on quantum systems
and
(b) local gate control of carbon nanotubes in order to define and control double
quantum dot systems in carbon nanotubes. As it turns out, local gates are
an important tool for increasing the control over quantum states in nanotubes.
The thesis is structured as follows:
• Chapter 1 gives a brief introduction to the chemical and electronic properties
of carbon nanotubes and the experimental procedures necessary for
manufacturing electrical devices with single carbon nanotubes.
• In Chapter 2 selected topics of charge transport in mesoscopic systems,
such as single and coupled quantum dots, are reviewed.
• In Chapter 3 we present electrical transport measurements through a carbon
nanotube coupled to a normal and a superconducting lead - a test
system for the exploration of the nature of many-particle correlations.
• Chapter 4 describes how to achieve local gate control over semiconducting
carbon nanotubes by adding top-gate electrodes.
• In Chapter 5 double quantum dots are defined and controlled inside a
carbon nanotube. The system allows for the observation of molecular
states induced by a large tunnel coupling of the dots; an artificial molecule
is defined inside a real one
Microfluidic systems for blood and blood cell characterization
No full textfirst_pagesettingsOrder Article Reprints
This is an early access version, the complete PDF, HTML, and XML versions will be available soon.
Open AccessReview
Microfluidic Systems for Blood and Blood Cell Characterization
by Hojin Kim 1,Alexander Zhbanov 2ORCID andSung Yang 2,3,*
1
Department of Mechatronics Engineering, Dongseo University, Busan 47011, Republic of Korea
2
School of Mechanical Engineering, Gwangju Institute of Science and Technology (GIST), Gwangju 61005, Republic of Korea
3
Department of Biomedical Science and Engineering, Gwangju Institute of Science and Technology (GIST), Gwangju 61005, Republic of Korea
*
Author to whom correspondence should be addressed.
Biosensors 2023, 13(1), 13; https://doi.org/10.3390/bios13010013
Received: 24 October 2022 / Revised: 16 December 2022 / Accepted: 19 December 2022 / Published: 22 December 2022
(This article belongs to the Section Nano- and Micro-Technologies in Biosensors)
Download Browse Figure Review Reports Versions Notes
Abstract
A laboratory blood test is vital for assessing a patient’s health and disease status. Advances in microfluidic technology have opened the door for on-chip blood analysis. Currently, microfluidic devices can reproduce myriad routine laboratory blood tests. Considerable progress has been made in microfluidic cytometry, blood cell separation, and characterization. Along with the usual clinical parameters, microfluidics makes it possible to determine the physical properties of blood and blood cells. We review recent advances in microfluidic systems for measuring the physical properties and biophysical characteristics of blood and blood cells. Added emphasis is placed on multifunctional platforms that combine several microfluidic technologies for effective cell characterization. The combination of hydrodynamic, optical, electromagnetic, and/or acoustic methods in a microfluidic device facilitates the precise determination of various physical properties of blood and blood cells. We analyzed the physical quantities that are measured by microfluidic devices and the parameters that are determined through these measurements. We discuss unexplored problems and present our perspectives on the long-term challenges and trends associated with the application of microfluidics in clinical laboratories. We expect the characterization of the physical properties of blood and blood cells in a microfluidic environment to be considered a standard blood test in the future.TRUEsciescopu
Superconducting On-Chip Spectrometery for Millimeter-submillimeter Wave Astronomy
No full textSince the birth of astrophysics, astronomers have been using free-space optics to analyze light falling on Earth. In the future however, thanks to the advances in photonics and nanoscience/nanotechnology, much of the manipulation of light might be carried out using not optics but confined waveguides, or circuits, on a chip. This new generation of instruments will be not only extremely compact, but also powerful in performance because the integration enables a greater degree of multiplexing. The benefit is especially profound for space- or air-borne observatories, where size, weight, and mechanical reliability are of top priority. Recently, several groups around the world are trying to integrate ultra-wideband (UWB), low-resolution spectrometers for millimeter-submillimeter waves onto microchips, using superconducting microelectronics. The scope of this Paper is to provide a general introduction and a review of the state-of-the-art of this rapidly advancing field.MicroelectronicsElectrical Engineering, Mathematics and Computer Scienc
Varieties of Exploratory Experimentation in Nanotoxicology
No full textThere has been relatively little effort to provide a systematic overview of different forms of exploratory experimentation (EE). The present paper examines the growing subdiscipline of nanotoxicology and suggests that it illustrates at least four ways that researchers can engage in EE: searching for regularities; developing new techniques, simulation models, and instrumentation; collecting and analyzing large swaths of data using new experimental strategies (e.g., computer-based simulation and “high-throughput” instrumentation); and structuring an entire disciplinary field around exploratory research agendas. In order to distinguish these and other activities more effectively, the paper proposes a taxonomy that includes three dimensions along which types of EE vary: (1) the aim of the experimental activity, (2) the role of theory in the activity, and (3) the methods or strategies employed for varying experimental parameters
