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The HeartWare HVAD is a radial rotary blood pump with a combination of passive magnetic and hydrodynamic bearings to levitate the impeller. The axial gap size between impeller and housing in this bearing and its sensitivity to speed, flow, and pressure difference is difficult to assess. Shear stresses are exceptionally high in this tiny gap making it important for blood damage and related adverse events. Therefore, the aim of this study was to measure the axial gap clearance in the HVAD at different operating conditions employing radiography. To quantify the gap size in the HVAD, the pump was positioned 30 mm in front of the X-ray source employing a microfocus X-ray tube with an acceleration voltage up to 300 kV. Beams were detected on a flat panel detector (Perkin Elmer XRD 1611-CP3). The pump was connected to a tubing circuit with a throttle to adjust flow (0, 5, 10 L/min) and a water glycerol mixture to set the desired viscosity (1, 4, 8 mPas). Rotational speed was varied between 1800 and 3600 rpm. In this study, for clinically relevant conditions at 5 L/min and 2700 rpm, the axial gap was 22 µm. The gap size increased with rotational speeds dependent on the viscosity (2.8, 6.9, and 9.4 µm/1000 rpm for 1, 4, and 8 mPas, respectively), but was independent from the volume flow and the pressure head at constant speeds. In summary, using X-ray radiographic imaging small gaps in a rotary blood pump during operation can be measured in a nondestructive contact-free way. The axial hydrodynamic bearing gap in the HVAD pump was determined to be in the range of about three times the diameter of a red blood cell. Its dependence on operating volume flow and generated pressure head across the pump is not pronounced.

This work reports on the development and the experimental proof of a novel concept of miniaturized X-ray source. This concept is based on microsystems technology and carbon nanotube electron field emitters. Thereby, unseen features such as fast switching and reduced imaging time will be enabled in future applications, such as, for instance, static computed tomography. In this work we describe the fabrication, assembly, and testing of micro-fabricated electrodes and carbon nanotube cold cathodes, based on a new design concept, to be packaged in a miniaturized X-ray source. The source design concept was experimentally validated. X-rays were generated with a total current of up to 4 μA extracted from the cathode and an acceleration voltage of 3.1 kV. The total current collected on the anode was 0.2–0.4 μA which thus corresponds to a collection efficiency on the anode of approx. 10%. The components were assembled and operated in a high vacuum chamber at −6 mbar. The achieved results from both, the electron and the X-ray emission experiments will be discussed in detail. Furthermore, we comment on the individual components’ limitations as well as on the next steps to be taken in order to optimize the characteristics and performance of the final X-ray source.

Palladium nanoparticles modified with the hexadecyl-2-hydroxyethyl-dimethylammonium dihydrogen phosphate (HHDMA) ligand have been stabilised within the microchannels of a metallic monolith coated with a high-surface area γ-alumina layer. The stainless steel skeleton of the monolith was 3D printed by stereolithography. The washcoating protocol has been optimised in order to maximise the γ-alumina loading without blocking the microchannels. A battery of techniques has been applied to characterise the properties and three-dimensional organisation of the phases within the monolithic reactor from the macro- to the nanoscale including N2 sorption, X-ray diffraction, thermogravimetric analysis, nuclear magnetic resonance and infrared spectroscopies, X-ray tomography, and optical or electron microscopies. Evaluation of the catalyst performance in the flow hydrogenation of acetylenic compounds of different size and functionality demonstrates the high efficiency and stability of the structured catalyst. Particularly, the monolithic reactor retains the intrinsic selective character of the hybrid palladium nanoparticles, even at high temperatures and pressures (T > 343 K and P > 5 bar). This is attributed to the improved isothermicity of the catalyst bed, deriving from the high thermal conductivity of the metallic skeleton of the monolith. Overall, the work provides a general route to prepare monolithic reactors based on Pd-HHDMA nanoparticles, bridging the gap between hybrid nanomaterial and reactor engineering.

We describe the design and present the performances of a charged particle telescope used for high resolution silicon pixel developments. A telescope made of four x and four y single-sided silicon microstrip layers was built, providing an r.m.s. position resolution of 1 μm for high energy charged particles. A signal over noise ratio of 130 was achieved with minimum ionizing particles.

The large magnetic field in modern high energy physics experiments can be used to improve the spatial resolution of large pitch silicon tracking detectors by ensuring charge sharing between neighbouring strips or pixels. For the reconstruction of the passing particle's track, the influence of the magnetic field on the drifting charge carriers must be known. One of the parameters is the Lorentz-angle which describes the change of the drift direction with respect to the electric field.

article i nfo Available online 14 August 2008 We have fabricated a series of p-i-n Ge/Si heterojunction photodetectors with different thicknesses of the intrinsic Ge layer, different doping levels of the p and n layers and different diode diameters. Epitaxial Ge was deposited on Si(100) using low-energy plasma-enhanced CVD (LEPECVD) followed by cyclic annealing. Dark current values as low as 0.04 mA/cm 2 were achieved for 1 μm thick p-i-n photodiodes on lightly doped substrates at −1 V bias, and external quantum efficiencies of 56% at 1.30 μm and 44% at 1.55 μm for 3 μm thick p + -i-n + photodiodes on highly doped substrates under 0.5 V reverse bias. For a 30 µm diameter diode a RC frequency of 21 GHz is obtained at a reverse bias of 1 V. With such characteristics, these diodes are attractive for telecommunication and optoelectronic applications.

A near-infrared image sensor with monolithically integrated Ge photodiodes is demonstrated. The technology for the integration of the Ge photodiodes into the CMOS process is outlined, and the measurement results of test-diodes and the full imager are discussed in detail. The heterojunction-photodiodes show a quantum efficiency of about 30% up to a wavelength of 1500 nm. A tensile strain of 0.17% was measured in the epitaxial Ge layer, which is in good agreement with the optically measured direct bandgap absorption edge of 1580 nm. The image sensor can be operated at room temperature or with moderate cooling.

A vertically illuminated photodetector based on Ge-on-SOI, which operates at 8 Gb/s for reverse bias as low as 0.5 V, is presented. The integrated photodetector also features low dark current and good photogenerated carrier collection efficiency.

Here we present results on heterojunction p-i-n photodiodes grown by Low-Energy Plasma-Enhanced CVD (LEPECVD). In a LEPECVD reactor the relatively thick Ge layers, required in NIR detectors, can be deposited in a few minutes at temperatures fully compatible with the CMOS process, making such deposition method appealing for this application.

The time-of-flight (TOF) principle is a well known principle to acquire a scene in all three dimensions. The advantages of the knowledge of the third dimension are obvious for many kinds of applications. The distance information within the scene renders automatic systems more robust and much less complex or even enables completely new solutions. A solid-state image sensor containing 124 x 160 pixels and the corresponding 3D-camera, the so-called SwissRanger camera, has already been presented in detail in [1]. It has been shown that the SwissRanger camera achieves depth resolutions in the sub-centimeter range, corresponding to a measured time resolution of a few tens of picoseconds with respect to the speed of light (c~3•108 m/s). However, one main drawback of these so-called lock-in TOF pixels is their limited capacity to handle background illumination. Keeping in mind that in outdoor applications the optical power on the sensor originating from background illumination (e.g., sun light) may be up to a few 100 times higher than the power of the modulated illumination, the sensor requires new pixel structures eliminating or at least reducing the currently experienced restrictions in terms of background illumination. Based on a 0.6 µm CMOS/CCD technology, four new pixel architectures suppressing background illumination and/or improving the ratio of modulated signal to background signal at the pixel-output level were developed and will be presented in this paper. The theoretical principle of operation and the expected performance are described in detail, together with a sketch of the implementation of the different pixel designs at silicon level. Furthermore, test results obtained in a laboratory environment are published. The sensor structures are characterized in a high background-light environment with up to sun light conditions. The distance linearity over a range of a few meters with the mentioned light conditions is measured. At the same time, the distance resolution is plotted as a function of the target distance, the integration time and the background illumination power. This in-depth evaluation leads to a comparison of the various background suppression approaches; it also includes a comparison with the traditional pixel structure in order to highlight the benefits of the new approaches. The paper concludes by providing parameter estimations which enables the outlook to build a sensor with a high lateral resolution containing the most promising pixel.

Monolithic integration of sensing devices usually requires sharing the CMOS chip floor space between sensors and their readout electronics. Vertical integration of the sensor on top of the electronics allows one to have the full chip area dedicated to sensing. For light detection, the deposition of hydrogenated amorphous silicon (a-Si:H) photodiodes on top of CMOS readout circuits offers several advantages compared to standard CMOS imagers. The issues regarding the design of a-Si:H photodiodes, their integration and the influence of the CMOS chip design (i.e. its surface morphology) on a-Si:H diode performance are discussed. Examples of TFA sensors for vision and particle detection are also presented.

A new miniaturised 256 pixel silicon line sensor, which allows for the acquisition of depth-resolved images in real-time, is presented. It reliably and simultaneously delivers intensity data as well as distance information on the objects in the scene. The depth measurement is based on the time-of-flight (TOF) principle. The device allows the simultaneous measurement of the phase, offset and amplitude of a radio frequency modulated light field that is emitted by the system and reflected back by the camera surroundings, without requiring any mechanical scanning parts. The 3D line sensor will be used on a mobile robot platform to substitute the laser range scanners traditionally used for navigation in dynamic and/or unknown environments.

A new miniaturized camera system that is capable of 3-dimensional imaging in real-time is presented. The compact imaging device is able to entirely capture its environment in all three spatial dimensions. It reliably and simultaneously delivers intensity data as well as range information on the objects and persons in the scene. The depth measurement is based on the time-of-flight (TOF) principle. A custom solid-state image sensor allows the parallel measurement of the phase, offset and amplitude of a radio frequency (RF) modulated light field that is emitted by the system and reflected back by the camera surroundings without requiring any mechanical scanning parts. In this paper, the theoretical background of the implemented TOF principle is presented, together with the technological requirements and detailed practical implementation issues of such a distance measuring system. Furthermore, the schematic overview of the complete 3D-camera system is provided. The experimental test results are presented and discussed. The present camera system can achieve sub-centimeter depth resolution for a wide range of operating conditions. A miniaturized version of such a 3D-solid-state camera, the SwissRanger 2, is presented as an example, illustrating the possibility of manufacturing compact, robust and cost effective ranging camera products for 3D imaging in real-time.