X-ray phase-contrast imaging has experienced rapid development over the last few decades, and, in this technology, the phase modulation strategy of phase stepping (PS) is used most widely to measure the sample’s phase signal. However, because of its discontinuous nature, PS has the defects of worse mechanical stability and high exposure dose, which greatly hinder its wide use in dynamic phase measurement and potential clinical applications. We demonstrate preliminary research on the use of integrating-bucket (IB) phase modulation method to retrieve the phase information in grating-based x-ray phase-contrast imaging. Experimental results show that our proposed method can be well employed to extract the differential phase-contrast image, compared with the commonly used PS strategy, the advantage of the IB phase modulation technique is that fast measurement and low dose are promising.
Grating-based x-ray phase contrast imaging has attracted significant attentions in the past years due to its capability in achieving x-ray phase contrast imaging with low brilliance source. The reverse projection (RP) method is a novel fast and low dose information extraction approach, which bases on the linear approximation of the shifting curve around its half-slope. However, when the refraction angle is beyond the linear range of the shifting curve, the extracted information is no longer credible. In this paper, we present an improved retrieval method by calculating an inverse function. Compared with the original retrieval method, our method does not rely on the first order approximation, and thus is suitable for large refraction angle. Theoretical derivations and numerical simulations are performed to confirm the accuracy of the method.
Cryo soft X-ray tomography (Cryo-SXT) is a valuable tool for high-resolution three dimensional (3D) imaging of cells in near-native preservation state. Cryo-immobilization of cells based on rapid cryogenic freezing is crucial to obtain good imaging in Cryo-SXT. In order to acquire high contrast image of live cells, it need to prepare the specimen ice as thin as possible. However, as the thickness of the ice layer is further reduced, the live cells may be destroyed during the tilt series data collection of 3D imaging due to radiation. Thus, it is essential to seek out a proper thickness range of the ice layer to get high contrast image without radiation damage of cells. For further understanding the relationship between thickness of ice layer and degree of radiation damage, yeast cells with different thickness of ice layer were imaged using Cryo-SXT. Finally the ice layer with thickness about 10 μm was confirmed to be proper for good imaging.
Composites of La0.4Sr0.6Co0.8Fe0.2O3−d (LSCF) with samarium doped ceria (SDC) have been extensively used as cathodes
for solid oxide fuel cells (SOFCs) to lower its operation temperature. The ability to visualize three-dimensional (3D)
microstructural changes in LSCF-SDC composite cathodes can help elucidate the impact of microstructure on cathode
performance. This study reports that we utilize the nano-computed tomography (nano-CT) technique to image the 3D
microstructures of La0.4Sr0.6Co0.2Fe0.8O3 (LSCF) - Ce0.8Sm0.2O1.9 (SDC) composite cathodes which were sintering at 800,
1000, and 1200°C, respectively, for 2 h based on the Fe K-absorption edge. Using the reconstructions of LSFC-SDC
composite cathodes submitted to different temperatures, the key microstructural properties, such as volume fraction of
each phase, connected volume fraction, surface area, triple-phase boundary length, and pore size were measured. The
effect of sintering temperature on the microstructure of LSFC-SDC cathodes was discussed and compared with
theoretical simulation. With increasing sintering temperature in the range from 800 to 1200°C LSFC-SDC composite
cathode microstructure was found that the volume fraction and grain size of LSCF material increased, while the volume
fraction of SDC decreased. Furthermore, the triple-phase boundary length per volume increased as the sintering
temperature increasing. This study had revealed that the nano-CT can provide a powerful tool to investigate the 3D
microstructure of energy materials and optimize its preparation condition to gain better functional performance.
Nano-CT has been considered as an important technique applied in analyzing inter-structures of nanomaterials and
biological cell. However, maximum rotation angle of the sample stage is limited by sample space; meanwhile, the scan
time is exorbitantly large to get enough projections in some cases. Therefore, it is difficult to acquire nano-CT images
with high quality by using conventional Fourier reconstruction methods based on limited-angle or few-view projections.
In this paper, we utilized the total variation (TV) iterative reconstruction to carry out numerical image and nano-CT
image reconstruction with limited-angle and few-view data. The results indicated that better quality images had been
achieved.
Planar parabolic refractive lenses are one important kind of compound refractive lenses which are used in the third generation synchrotron radiation sources as an x-ray focusing device.
In order to test the influence of the number of the individual lens on the transmission and gain, a set of 30 micro-focusing planar parabolic lenses with different number (from 1 to 30) of the individual lens was designed, which had equal apertures of 250 μm and equal focal length of 30 cm at 8.05 keV. The parameters of the lenses were optimized for performing focusing test at x-ray diffractometer (XRD). The optical simulation was completed by ray tracing by the commercial program of ZEMAX. The radius of curvature at the tip of the parabola ranged from 1.23 μm to 37 μm and the theoretical transmission from 43.3 % to 33.2 %. The theoretical width of focal line was about 3.4 μm. Ultra violet lithography was used to fabricate the planar lenses from SU-8 photoresist which
thickness was 224 μm. Measured dimension of lenses is coincident with the theoretical one. Focusing properties of the lenses were studied both at XRD and at U7B beamline at the National Synchrotron
Radiation Laboratory (NSRL) at the energy of 8.05 keV. The detector was a Peltier-cooled, 1380 x 1030 format (6.45 x 6.45 μm2 pixels) charge coupled device with a fiber-optic-coupled scintillator (Photonic Sciences Ltd., "X-ray Fast Digital Imager"). The width of focal line was about 27.4 μm with a gain of 7.17 for N=8 lenses which was achieved in the NSRL. The reasons for the big difference between theoretical values and measured ones were discussed.
Most previous research on electroplating in LIGA has focused on electrodeposition of metal into high aspect ratio resist molds. In overplating process how the metal grows up across the top of resist molds has been relatively neglected. Typical defects like holes formation at the top of cavities of electroplated metal mold usually occur due to improper process control especially when the space/linewidth ratio of microstructure increases. To help understand these problems, overplating process has been investigated. A model is developed to compute current density distribution based on LIGA mold feature using electroplating simulation tools. Results show that it is almost an isotropic growing model at the first stage of overplating. As the deposited metal grows bigger the space between electrodes is shortened and the current density distribution along electrode may be modulated by neighbor electrode. It doesn't show an isotropic growing model any more. The deposition rate in inward lateral direction is smaller than in vertical direction. The growing model based on calculation shows that the trench feature aspect ratio can reach a considerable magnitude especially when the LIGA mold feature space/linewidth ratio increases. In poor transport situation, ion depletion becomes significant and a stopped deposition may occur thus holes can be formed at the bottom of overlapped neighbor electrodes. An optimized experiment has been performed using low overpotentials at the stage before the overlapping of neighbor electrodes and a rigorous stirring of electrolyte. A nickel mold insert without holes-formation defects can be obtained.
Three dimensions photonic crystals represent one of the most important building blocks towards the achievement of a full optics communication technology. Although several methods have been demonstrated to prepare 3D photon crystals, 3D photonic crystals still represent a challenge to a fabrication point of view. It is highly desirable that the fabrication of these 3D structures involves simple technologies. In this paper, a novel method has been developed to fabricate 3D photonic crystals structure. The process of multi deep X-ray lithography is: Firstly, the cube or cuboid of resist sample is shaped by lathe. Then, the microstructures are patterned by three times deep X-ray lithograph through three surfaces that are vertically each other. After development, the 3D PC structure is obtained. The 3D photonic crystals structures are fabricated to demonstrate this method. The result shows that this method can avoid many problems caused by tilt X-ray lithography and the lattice layer is enough to meet the requirement of 3D photonic crystals. It is simple and effective to realize the 3D photonic crystals structure by using multi deep X-ray lithography. And various 3D photonic crystals types and lattice defects can be achieved by using this method.
With holographic-ion beam etching technique, a number of self-supporting transmission gratings have been fabricated for inertial confinement fusion diagnosis. In addition to the general process, a practical method for monitoring the evolution of the grating structures exposed in photoresist during development of the resist. The real-time monitor technique developed here is relatively simple in comparison with a He-Ne laser and detector, which needs delicate control.
The microtribology phenomena on the micro contact (or slide) surface, where the effects of surface forces are more significant than those of gravity, is very different with the conventional machine. The friction force that works on a friction face of a microsystems is significantly high relative to the size of the machine, the fluid lubrication in the conventional size mechanical parts cannot reduce the friction force on the microsystems, the solid lubrication (self- lubrication) should be applied to reduce the friction force. In this paper, the solid lubrication MoS2 was studied. MoS2 is embedded into the Ni structure in electroforming process. The results show that MoS2 can be used as the solid lubrication in the microsystems to reduce the friction force and enhance the hardness of microsystem.
In the late of this century the great success of VSIC impacts into almost every fields of our social. Following this idea people starts to integrate microsensor microprocessor and microactuators into a small space to forming a Micro Electro and Mechanical System. Such small robot parts are applied to including satellites, computer communication, medical, chemical, biological and environment and so on research fields. The development of MEMS would strongly influence industrial revolution in the next century. LIGA technology including X-ray deep etching lithography; electroplating and plastic molding developed by Karlsruhe Nuclear Research Center, Germany since the beginning of 1980. Its advantages are: it could make three-dimensional microstructures with lateral dimension in several micron range and thickness of several hundred microns with sub-micron precision. In principle all kinds of materials such as polymer, metal and ceramic could be used as microcomponents and could be mass- produced by plastic molding to a commercially available fabrication. LIGA process has become one of the most promising Microfabrication technologies for producing micromechanical, microfluid and micro-optical elements. It opens an additional field in the microstructure market.
In this paper a brief description is given to introduce the activities of the manufacturing technology using the synchrotron radiation light source in the National Synchrotron Radiation Laboratory (NSRL). The light source in NSRL is a dedicated synchrotron radiation facility in China. Five beamlines and corresponding experimental stations, including soft x-ray lithography, have been constructed. The main experimental results obtained from the soft x-ray lithography station are reported. We have fabricated some devices using the synchrotron radiation lithography, for example, the high electron mobility transistor, high Tc superconductor infrared detector-array, diffraction grating, and micro condenser zone plate. A simple method for the achievement of synchrotron radiation x-ray lithography mask will also be presented. The LIGA (German abbreviation for: Lithograpie, Galvanoforming, and Abforming) technique has been developed in NSRL. It is the most promising technique for the fabrication of three-dimensional microstructures. We are successful in making several microdevices by deep x-ray lithography and microelectroforming, such as microgearwheel, micro acceleration sensor.
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