Airborne Visible/Infrared Imaging spectrometer AVIS: Design, characterization and calibration

The Airborne Visible/Infrared imaging Spectrometer AVIS is a hyperspectral imager designed for environmental monitoring purposes. The sensor, which was constructed entirely from commercially available components, has been successfully deployed during several experiments between 1999 and 2007. We describe the instrument design and present the results of laboratory characterization and calibration of the system's second generation, AVIS-2, which is currently being operated. The processing of the data is described and examples of remote sensing reflectance data are presented

Magneto-optical imaging of magnetic flux patterns in superconducting films with antidots

Superconducting YBaCuO thin films were equipped with a special arrangement of antidots (holes) of 1 micron radius in order to guide the stream of magnetic flux moving in (or out of) the sample. The flux distribution and its dynamics were visualized using real-time magneto-optical imaging. It is clearly demonstrated that one-dimensional antidot arrays strongly facilitate propagation of magnetic flux. We also demonstrate a possibility to alter the direction of flux motion in a controlled way by special arrangement of intercepting antidot arrays. Our resolution was sufficient for observation of flux in particular antidots, which allows a more detailed dynamic analysis of such systems.Comment: 4 pages, 5 figures, submitted to Physica C, Proc. of VORTEX-IV Workshop on Crete-200

Direct observation of vortices in an array of holes at low temperature: temperature dependance and first visualization of localized superconductivity

A scanning micro superconducting quantum interference device (microSQUID) microscope is used to directly image vortices in a superconducting Al thin film. We observe the temperature dependence of the vortex distribution in a regular defect (hole) array patterned into the Al film. The first direct observation of the localized superconducting state around the holes is shown as well as the effect of the hole size on nucleation of the superconducting state

Development of an image converter of radical design

A long term investigation of thin film sensors, monolithic photo-field effect transistors, and epitaxially diffused phototransistors and photodiodes to meet requirements to produce acceptable all solid state, electronically scanned imaging system, led to the production of an advanced engineering model camera which employs a 200,000 element phototransistor array (organized in a matrix of 400 rows by 500 columns) to secure resolution comparable to commercial television. The full investigation is described for the period July 1962 through July 1972, and covers the following broad topics in detail: (1) sensor monoliths; (2) fabrication technology; (3) functional theory; (4) system methodology; and (5) deployment profile. A summary of the work and conclusions are given, along with extensive schematic diagrams of the final solid state imaging system product

Flexible Neural Electrode Array Based-on Porous Graphene for Cortical Microstimulation and Sensing.

Neural sensing and stimulation have been the backbone of neuroscience research, brain-machine interfaces and clinical neuromodulation therapies for decades. To-date, most of the neural stimulation systems have relied on sharp metal microelectrodes with poor electrochemical properties that induce extensive damage to the tissue and significantly degrade the long-term stability of implantable systems. Here, we demonstrate a flexible cortical microelectrode array based on porous graphene, which is capable of efficient electrophysiological sensing and stimulation from the brain surface, without penetrating into the tissue. Porous graphene electrodes show superior impedance and charge injection characteristics making them ideal for high efficiency cortical sensing and stimulation. They exhibit no physical delamination or degradation even after 1 million biphasic stimulation cycles, confirming high endurance. In in vivo experiments with rodents, same array is used to sense brain activity patterns with high spatio-temporal resolution and to control leg muscles with high-precision electrical stimulation from the cortical surface. Flexible porous graphene array offers a minimally invasive but high efficiency neuromodulation scheme with potential applications in cortical mapping, brain-computer interfaces, treatment of neurological disorders, where high resolution and simultaneous recording and stimulation of neural activity are crucial

A high aspect ratio Fin-Ion Sensitive Field Effect Transistor: compromises towards better electrochemical bio-sensing

The development of next generation medicines demand more sensitive and reliable label free sensing able to cope with increasing needs of multiplexing and shorter times to results. Field effect transistor-based biosensors emerge as one of the main possible technologies to cover the existing gap. The general trend for the sensors has been miniaturisation with the expectation of improving sensitivity and response time, but presenting issues with reproducibility and noise level. Here we propose a Fin-Field Effect Transistor (FinFET) with a high heigth to width aspect ratio for electrochemical biosensing solving the issue of nanosensors in terms of reproducibility and noise, while keeping the fast response time. We fabricated different devices and characterised their performance with their response to the pH changes that fitted to a Nernst-Poisson model. The experimental data were compared with simulations of devices with different aspect ratio, stablishing an advantage in total signal and linearity for the FinFETs with higher aspect ratio. In addition, these FinFETs promise the optimisation of reliability and efficiency in terms of limits of detection, for which the interplay of the size and geometry of the sensor with the diffusion of the analytes plays a pivotal role.Comment: Article submitted to Nano Letter

Array atomic force microscopy for real-time multiparametric analysis.

Nanoscale multipoint structure-function analysis is essential for deciphering the complexity of multiscale biological and physical systems. Atomic force microscopy (AFM) allows nanoscale structure-function imaging in various operating environments and can be integrated seamlessly with disparate probe-based sensing and manipulation technologies. Conventional AFMs only permit sequential single-point analysis; widespread adoption of array AFMs for simultaneous multipoint study is challenging owing to the intrinsic limitations of existing technological approaches. Here, we describe a prototype dispersive optics-based array AFM capable of simultaneously monitoring multiple probe-sample interactions. A single supercontinuum laser beam is utilized to spatially and spectrally map multiple cantilevers, to isolate and record beam deflection from individual cantilevers using distinct wavelength selection. This design provides a remarkably simplified yet effective solution to overcome the optical cross-talk while maintaining subnanometer sensitivity and compatibility with probe-based sensors. We demonstrate the versatility and robustness of our system on parallel multiparametric imaging at multiscale levels ranging from surface morphology to hydrophobicity and electric potential mapping in both air and liquid, mechanical wave propagation in polymeric films, and the dynamics of living cells. This multiparametric, multiscale approach provides opportunities for studying the emergent properties of atomic-scale mechanical and physicochemical interactions in a wide range of physical and biological networks

Feasibility of thickness mapping using ultrasonic guided waves

Detection and sizing of corrosion in pipelines and pressure vessels over large, partially accessible areas is of growing interest in the petrochemical and nuclear industries. Traditionally, conventional ultrasonic thickness gauging and eddy current techniques have been used to precisely measure the thickness in structures. These techniques only allow the measurement of the local thickness under the probe. Consequently obtaining the remnant thickness of a specimen over a large area requires the probe to be scanned, which is a long and tedious process. Moreover, with these techniques, the scanning may become impossible when the area of inspection is inaccessible. There is therefore a need for a rapid, accurate, long range inspection technique to measure the remaining thickness in corrosion patches. Low frequency guided waves are now routinely used to screen large area of pipes and other structures for cracks and corrosion. Their detection and location capability is very good, but the standard screening technique only gives a rough estimate of the remaining wall thickness. Guided waves have multiple properties which can be used for thickness mapping over large partially accessible areas e.g. dispersion and cutoff frequency thickness product of the high order modes. The present work aims to demonstrate the potential of guided waves for thickness mapping over large partially accessible areas. It starts with a general introduction on ultrasonic guided waves and a literature review of the different techniques for the evaluation of thickness with guided waves. The severity of the errors introduced in time-of-flight tomography for thickness reconstruction by breaking the assumption of the ray theory are investigated. As these errors are significant, the possibility of using the cutoff property of the high order modes is investigated in a frequency range where the ray theory is valid. It is found that the attenuation due to the scattering of the waves in corrosion is too large for this technique to work. Finally the use of low frequency guided wave for diffraction tomography is examined. Finite element simulations of a 64 element circular array on a plate show that when the scattering mechanism of the object to be reconstructed satisfies the Born approximation the reconstruction of the thickness is accurate. However the practical implementation is more challenging when the incident field is not known. Experimental results demonstrate that ultimately the scattering from the array of transducer is a major source of error in the tomographic reconstruction, but when there is no scattering from the array of transducers the reconstructions are very similar to the finite element simulations

NIKA: A millimeter-wave kinetic inductance camera

Current generation millimeter wavelength detectors suffer from scaling limits imposed by complex cryogenic readout electronics. To circumvent this it is imperative to investigate technologies that intrinsically incorporate strong multiplexing. One possible solution is the kinetic inductance detector (KID). In order to assess the potential of this nascent technology, a prototype instrument optimized for the 2 mm atmospheric window was constructed. Known as the N\'eel IRAM KIDs Array (NIKA), it was recently tested at the Institute for Millimetric Radio Astronomy (IRAM) 30-meter telescope at Pico Veleta, Spain. The measurement resulted in the imaging of a number of sources, including planets, quasars, and galaxies. The images for Mars, radio star MWC349, quasar 3C345, and galaxy M87 are presented. From these results, the optical NEP was calculated to be around $1 \times 10^{-15}$ W$/$Hz$^{1/2}$. A factor of 10 improvement is expected to be readily feasible by improvements in the detector materials and reduction of performance-degrading spurious radiation.Comment: Accepted for publication in Astronomy & Astrophysic