X-Ray Imaging of the Filling of “T” Shaped Microchannel Using a MEDIPIX2 Pixel Detector

Fluid flows in “T” or “Y” shaped structures of microchannels are studied in order to develop modeling approaches as well as adapted measurement techniques. The applications of these structures are numerous and concern in particular biology and chemical engineering for which the integration of microchannels in lab-on-chip and/or microreactor is an important challenge. Our works concern the development of a measurement technique for the study of the filling of a “T” shaped microchannel structure by a liquid. In the studied channels, the experimental constraints are strong. Indeed, the space steps involved within the phenomena are very much reduced and vary from 1 to 10 μm. Moreover, the dynamics of the flow implies a high acquisition frequency, ranging from 10 to 100 Hz. Our technological choice is based on the measurement of the attenuation of an X-ray beam in the matter. The main advantage of this non-intrusive technique is that it can be implemented even in media opaque to visible light. Also, that X-ray techniques can theoretically reach a better space resolution than optical ones. The measurement technique is quantitative and a 3D measurement is achievable by tomography. These methods are validated for problems located at centimetric space steps and high acquisition frequencies, [1], [2]. The objective of this work is to match the microfluidics field requirement (space steps and attenuation contrast), while preserving high time frequencies. Our experimental bench consists of a X-ray generator, that makes possible to obtain high enlargements of the observed object whit a reduced blur in the image. The image is obtained by a pixel detector called Medipix2. This detector is under development within a European collaboration which gathers 16 partners around the CERN, the CEA being a partner. The main assets of this detector are its high space resolution, its operational photon counting mode and its high acquisition frequency. The presented works constitute a very first implementation and validation of the proposed technique for the microfluidics field. Experimental results are obtained and presented. They allow a measurement of the filling conditions of the “T” shape structure of microchannels. The orientations and research perspectives to improve the obtained results by the technique could be evaluated accurately and important basis of our work are now established and quantified for the future.

High-Energy Small- and Wide-Angle X-Ray Scattering: A Versatile Tool for Materials Analysis

Acquisition of microstructural information during realistic service conditions is an ongoing need for fundamental materials insight and computational input. In addition, for engineering applications it is often important to be able to study materials over a wide range of penetration depths, from the surface to bulk. In this presentation we discuss developments at the Sector 1-ID beamline of the Advanced Photon Source (APS) to utilize high-energy x-ray scattering for such studies. The use of high-energies (~80 keV) provides a highly penetrating probe, with sampling depths up to several mm in most materials. Through the development and use of high-energy optics, we can perform both small- and wide-angle scattering (SAXS/WAXS), to probe a large range of sample dimensions in reciprocal space (ranging from Angstroms to hundreds of nanometers), with real space resolutions ranging from microns to mm.

Three-Dimensional High-Resolution Optical/X-Ray Stereoscopic Tracking Velocimetry

Measurement of three-dimensional (3-D) three-component velocity fields is of great importance in a variety of research and industrial applications for understanding materials processing, fluid physics, and strain/displacement measurements. The 3-D experiments in these fields most likely inhibit the use of conventional techniques, which are based only on planar and optically-transparent-field observation. Here, we briefly review the current status of 3-D diagnostics for motion/velocity detection, for both optical and x-ray systems. As an initial step for providing 3-D capabilities, we have developed stereoscopic tracking velocimetry (STV) to measure 3-D flow/deformation through optical observation. The STV is advantageous in system simplicity, for continually observing 3-D phenomena in near real-time. In an effort to enhance the data processing through automation and to avoid the confusion in tracking numerous markers or particles, artificial neural networks are employed to incorporate human intelligence. Our initial optical investigations have proven the STV to be a very viable candidate for reliably measuring 3-D flow motions. With previous activities are focused on improving the processing efficiency, overall accuracy, and automation based on the optical system, the current efforts is directed to the concurrent expansion to the x-ray system for broader experimental applications.

Engineering Applications of Synchrotron X-Rays and Neutrons and the FaME38 Project

Large Central Scientific Facilities such as the ESRF (the European Synchrotron Radiation Facility) and ILL (the European centre for neutron research), were set up to provide scientists with the advanced facilities they need to exploit neutron and synchrotron X-ray beams for scientific research. Engineers also conduct research at these Facilities, but this is less common as most practicing engineers generally have little or no knowledge of neutron or X-ray scattering, or of their considerable potential for engineering research, model validation, material development and for fatigue and failure analysis. FaME38 is the new joint support Facility for Materials Engineering, located at ILL-ESRF, set up to encourage and to facilitate engineering research by engineers at these facilities. It provides a technical and knowledge centre, a materials support laboratory, and the additional equipment and resources that academic and industrial engineers need for materials engineering research to become practicable, efficient and routine. It enables engineers to add the most advanced scientific diffraction and imaging facilities to their portfolio of diagnostic tools. These include non-destructive internal and through-surface strain scanning, phase analysis, radiography and tomography of engineering components. Synchrotron X-ray and neutron diffraction strain mapping is particularly suited for the rigorous experimental, non-destructive, validation of Finite Element and other computer model codes used to predict residual stress fields that are critical to the performance and lifetimes of engineering components. This paper discusses the FaME38 facility and demonstrates its utility in gaining fundamental insight into mechanical engineering problems through examples, including studies of railway rails, welds and peened surfaces that demonstrate the potential of neutron of synchrotron X-ray strain scanning for the determination of residual stress fields in a variety of engineering materials and critical components.

X-Rays for Fluid Flow Inspection

X-rays techniques are widely used in the non-destructive evaluation field for mechanical inspection. However, development of new x-ray detectors and sources over the last decade has let to an intensive use of this technique in other fields. In this paper, we describe the use of X-rays techniques in the field of fluid flow engineering (fluidics and heat transfer). This technique is very attractive since measurements can be performed even if pressure, temperature require the use of opaque walls. In addition the X-ray technique is well suited to multiphase flows where optical technique can not be used if void fraction is larger than few percents. Specific gravity, mass or void fraction are the main accessible parameters.

High-Resolution Radiography for Detecting and Measuring Micron-Scale Features

X-ray radiography has long been recognized as a valuable tool for detecting internal features and flaws. Recent developments in microfabrication and composite materials have extended inspection requirements to the resolution limits of conventional radiography. Our work has been directed toward pushing both detection and measurement capabilities to a smaller scale. Until recently, we have used conventional contact radiography, optimized to resolve small features. With the recent purchase of a nano-focus (sub-micron) x-ray source, we are now investigating projection radiography, phase contrast imaging and micro-computed tomography (μ-CT). Projection radiography produces a magnified image that is limited in spatial resolution mainly by the source size, not by film grain size or detector pixel size. Under certain conditions phase contrast can increase the ability to resolve small features such as cracks, especially in materials with low absorption contrast. Micro-computed tomography can provide three-dimensional measurements on a micron scale and has been shown to provide better sensitivity than simple radiographs. We have included applications of these techniques to small-scale measurements not easily made by mechanical or optical means. Examples include void detection in meso-scale nickel MEMS parts, measurement of edge profiles in thick gold lithography masks, and characterization of the distribution of phases in composite materials. Our work, so far, has been limited to film.

Very Deep X-Ray Lithography for Heat and Mass Transfer Applications

Heat and mass transfer devices are being fabricated by International Mezzo Technologies that utilize micro features with increasingly aggressive combinations of both feature height and feature aspect ratio. Improvements in x-ray lithography using SU-8 now make it possible to lithographically define densely packed arrays of features with heights of 3 mm and with aspect ratios of around 25. These arrays potentially serve as the starting point for increasingly aggressive LIGA-based micro machining of heat exchangers, regenerators, recuperators, etc. that have superior performance due to length scale advantage.

Fabrication and Testing of Micro Corona Motor and Micro Gas Bearings

The paper introduces fabrication processes of a micro corona motor and micro gas bearings via X-ray lithography. The micro corona motor was fabricated using a membrane-less built-on X-ray mask. The motor principle requires axially thick sharp stator electrodes. Therefore, X-ray lithography was adopted for precise, high aspect ratio characteristics. To minimize diffraction, a built-on X-ray mask (conformal mask) technique was employed with negative toned SU-8 photo resist. This technique may be suitable for fast fabrication of prototypes or very tall structures, which can be largely affected by printing gaps. Micro gas bearings were fabricated as a viable bearing system for the micro corona motor. Timembrane mask was fabricated to meet the strict performance requirements and geometric constraints of the micro gas bearing. Test results of the micro gas bearings and micro corona motor are also presented.

Spatially Resolved Energy Dispersive X-Ray Diffraction (EDXRD) as a Tool for Nondestructively Providing Phase Composition Depth Profiles on Cement and Other Materials

The presence of sulfates in water or soils surrounding portland cement concrete structures leads to progressive degradation. Spatially resolved energy dispersive diffraction (EDXRD) in combination with computed microtomography (μCT) and mechanical measurements can provide the information needed to understand, in detail, the degradation mechanisms that are associated with sulfate attack and to validate accelerated test methods used to evaluate the sulfate resistance of cements. Highly penetrating, high-energy X-rays from synchrotron sources allow the use of EDXRD to nondestructively determine depth profiles for the crystalline phases in the cement paste specimens several millimeters below the sample surface. These depth profiles, and how they vary with sulfate exposure conditions and duration, can be correlated with mechanical changes and the crack patterns seen in the microtomographs. Spatially resolved EDXRD is in principle useful for phase composition mapping and depth profiling in a wide range of materials where the attenuation of high energy x-rays is not extreme. Suitable materials include many ceramic compositions.

Scanning X-Ray Microdiffraction for Materials Science at the Advanced Light Source

With the advent of high brilliance synchrotron sources and outstanding progress made in X-ray focusing optics, intense sub-micron X-ray beams are now routinely produced at several synchrotron facilities around the world. At the Advances Light Source, a dedicated Scanning X-ray Microdiffraction beamline using either white or monochromatic X-ray focused beam has been developed and is used for mapping grain orientation, strain/stress or crystalline species distribution in various samples with micron to submicron spatial resolution. It also allows for the study of local plasticity as well as for the characterization or identification of new crystalline structures. The facility and its capabilities are described through the study of the electromigration phenomenon in Al(Cu) and Cu interconnect test structures.