X-ray phase-contrast tomographic microimaging is a powerful tool to reveal the internal structure of opaque soft-matter objects that are not easily seen in standard absorption contrast. In such low Z materials, the phase shift of X-rays transmitted can be important as compared to the absorption. An easy experimental set up that exploits refractive contrast formation can deliver images that are providing detailed structural information. Applications are abundant in fields
including polymer science and engineering, biology, biomedical engineering, life sciences, zoology, water treatment and filtration, membrane science, and micro/nanomanufacturing. However, available software for absorptive contrast tomography cannot be simply used for structure retrieval as the contrast forming effect is different. In response, CSIRO has developed a reconstruction code for phase-contrast imaging. Here, we present a quantitative comparison of a micro phantom manufactured at SSLS with the object reconstructed by the code using X-ray images taken at SSLS. The phantom is a 500 μm thick 800 μm diameter cylindrical disk of SU-8 resist having various eccentric cylindrical bores with diameters ranging from 350 μm to 40 μm. Comparison of these parameters that are well known from design and post-manufacturing measurements with reconstructed ones gives encouraging results.
Up to date, electromagnetic metamaterials (EM<sub>3</sub>) have been mostly fabricated by primary pattern generation via electron beam or laser writer. Such an approach is time-consuming and may have limitations of the area filled with structures.
Especially, electron beam written structures are typically confined to areas of a few 100×100 μm<sup>2</sup>. However, for meaningful technological applications, larger quantities of good quality materials are needed. Lithography, in particular X-ray deep lithography, is well suited to accomplish this task. Singapore Synchrotron Light Source (SSLS) has been applying its LIGA process that includes primary pattern generation via electron beam or laser writer, X-ray deep
lithography and electroplating to the micro/nano-manufacturing of high-aspect ratio structures to produce a variety of EM<sup>3</sup> structures. Starting with Pendry's split ring resonators, we have pursued structure designs suitable for planar lithography since 2002 covering a range of resonance frequencies from 1 to 216 THz. More recently, string-like structures have also been included. Latest progress made in the manufacturing and characterization of quasi 3D
metamaterials having either split ring or string structures over areas of about ≈1 cm<sup>2</sup> extension will be described.
This paper summarizes the studies on meshfree point interpolation method (PIM) for static and dynamic analysis of piezoelectric structures. In the PIM methods, the problem domain is represented by a set of properly scattered nodes. The displacements and the electric potential of a point are interpolated by the values of nodes in its local support domain using shape functions derived from point interpolation scheme. Galerkin formulation is used to establish a set of system equations for arbitrary-shaped piezoelectric structures. Numerical examples are presented to demonstrate the validity and convergence of the present method and their results compare well with the conventional FEM results from ABAQUS as well as the experimental ones.
Adhesive bonding has been accepted as an important process in the manufacturing and repair industries. However, the tendency of delamination at the bonded region due to improper bonding procedures, and unfavorable loading conditions and service environment has necessitated development of reliable inspection techniques for ensuring the structural integrity of these bonded structures. Optical inspection techniques have, over the last three decades since the invention of the laser, gained wide acceptance because they are non-destructive and non-contacting, and accurate measurements in the order of light-wavelengths may be obtained very rapidly. Optical flaw-detection generally requires the application of a load-increment on the structure, the response of the illuminated surface of the structure is then compared with that of a non-defective structure. The load-increments used are in various forms, such as vacuum stressing, heating, static mechanical loads, and steady-state mechanical excitations.
Control of the sound reflection from an underwater object is a very important issue. Active piezoelectric layers properly coated on the external surface of the object can control the reflection of incident sound waves. In many active control systems, a sensing device must be employed for the detection of the incident sound. The detected signal is then fed to properly controlled actuators to produce a sound wave to cancel the sound reflection. Multi-layered active coatings are therefore employed, which includes layers of acoustic sensor, layers of actuators and layers of encapsulant. The paper addresses the applications of the active acoustic coating with piezoelectric sensors and actuators for the cancellation of underwater sound reflection and transmission in the frequency domain. Computational techniques are reviewed on analyzing multi-layered active coating systems and on calculating the voltages required for the piezoelectric layers to cancel underwater sound reflections and/or transmissions. Non-reflective piezoelectric coatings are discussed for a oblique and/or normal plane sound wave incidence. The formulations such as surface impedance tensor approach and transfer matrix approach are introduced. They account for the complex interaction between the sound waves and the submerged active coating. The design criterion of imbedded sensors in the multi-layered active non-reflective coating is considered.