Tadashi Hattori

Phase tomography by X-ray talbot interferometry for biological imaging

The X-ray phase tomography of biological samples is reported, which is based on X-ray Talbot interferometry. Its imaging principle is described in detail, and imaging results obtained for a cancerous rabbit liver and a mouse tail with synchrotron radiation are presented. Because an amplitude grating is needed to construct an X-ray Talbot interferometer, a high-aspect-ratio grating pattern was fabricated by X-ray lithography and gold electroplating. X-ray Talbot interferometry has an advantage that it functions with polychromatic cone-beam X-rays. Finally, the compatibility with a compact X-ray source is discussed.

X-ray phase imaging: from synchrotron to hospital.

With the aim of clinical applications of X-ray phase imaging based on Talbot–Lau-type grating interferometry to joint diseases and breast cancer, machines employing a conventional X-ray generator have been developed and installed in hospitals. The machine operation especially for diagnosing rheumatoid arthritis is described, which relies on the fact that cartilage in finger joints can be depicted with a dose of several milligray. The palm of a volunteer observed with 19 s exposure (total scan time: 32 s) is reported with a depicted cartilage feature in joints. This machine is now dedicated for clinical research with patients.

Development of Three Dimensional LIGA Process to Fabricate Spiral Microcoil

The LIGA process has been developed as a 2.5-dimensional processing method on Si wafers to date. However, we have succeeded in extending the LIGA process to 3D for the first time. 3D-LIGA was achieved by the technical development of 3D X-ray lithography and worm injection molding replication technology with unscrewing. These technologies began from the development of equipment and have developed into quite original technologies. By combining this 3D-LIGA process with a metallization technique that consists of flat and smooth electroplating and isotropic chemical etching, a spiral copper microstructure with a linewidth of 10 µm, a pitch of 20 µm and a thickness of 2 µm was formed on a cylindrical surface made from LCP with a length of 1 mm and a diameter of 0.48 mm. Furthermore, we applied the process to fabricate a spiral microcoil and estimated the electrical properties of the microcoil. The numbers of turns were 15, the inductance was 91 nH and the quality factor was 5.8 for a frequency of 1 GHz. Direct-current resistance was measured as 99 Ω.

X-Ray Phase Imaging with Single Phase Grating

X-ray phase imaging with a single phase grating based on the fractional Talbot effect is described. A phase grating with an 8 µm pitch was placed behind a weakly absorbing object and illuminated with partially coherent 17.7 keV X-rays. Intensity patterns downstream of the grating were recorded with a high-resolution image detector. By the fringe scanning method, an X-ray wavefront inclination by the object was obtained. Phase tomography was performed and the three-dimensional structure of a piece of a polymer blend was revealed with an 8 µm spatial resolution and a 9 mg/cm3 detection limit of density deviation.

Differential Phase X-ray Imaging Microscopy with X-ray Talbot Interferometer

A new type of differential phase X-ray imaging microscopy attained by combination of an X-ray imaging microscope and an X-ray Talbot interferometer is described. An X-ray Talbot interferometer was set up so that a moire-fringe pattern appeared on the image plane of an X-ray imaging microscope. The wavefront inclination (differential phase shift) caused by a weakly absorbing polymer sample was measured from the fringes using the fringe-scanning method and with a spatial resolution of 1 µm. Phase tomography was also performed and the internal structures of a piece of polymer blend were depicted.

Biomedical imaging by Talbot-type x-ray phase tomography

An X-ray Talbot interferometer for X-ray phase imaging and tomography was constructed using an amplitude grating of a gold pattern 8 μm in pitch and 30 μm in height developed by X-ray lithography and gold electroplating. The effective area of the grating was 20 mm x 20 mm, and was fully illuminated by synchrotron radiation at beamline 20XU, SPring-8, Japan. Almost whole body of a fish 3 cm in length was observed by phase tomography. Resulting images obtained with 0.07 nm and 0.045 nm X-rays revealed organs with bones in the same view successfully. A preliminary result of the combination with an X-ray imaging microscope is also presented, which was attempted to attain a higher spatial resolution. Finally, prospects of the compatibility with a conventional X-ray generator are discussed for practical applications such as clinical diagnoses.

Basic experiments of three-axis tactile sensor using optical flow

Three-axis tactile sensing has advantages for grasping an object of unknown mass and hardness. We developed a new three-axis tactile sensor that possesses a simple structure to endure a large applied force from a powerful grasp. Normal force distribution is measured based on grayscale values obtained by image data processing, as with previous three-axis tactile sensors. Tangential force distribution is determined by the linear movement of image data calculated by optical flow. The sensing characteristics of this sensor are dominated by the configuration and material of fine conical feelers formed on a silicon rubber sheet. By UV-LIGA, we obtain a fine mold of a silicon rubber sheet. In evaluation experiments, we applied both normal and tangential force to the sensor and confirmed this tactile sensors ability to acquire normal and tangential forces. In its design, we utilize a USB microscope that has a CMOS camera and a light source. In a series of experiments, we performed normal and tangential force tests to obtain its basic characteristics. The linear relationship between the grayscale value and the normal force is obtained from the normal force test. If the average optical flow is under 0.2 mm, the tangential force is proportional to the average optical flow. The slope of the relationship between the tangential force and the average optical flow increases with additional normal force. Finally, we derive a series of equations for three-axis force calculation.

Fabrication of Coil Lines with High Aspect Ratio for Electromagnetic Actuators

Actuators are finding increasing use in the various fields. And, it is one of most important parts for machines because it determines its performance. Actuators account for a large percentage and volume and weight of a product compared with other parts. Therefore, the progress in downsizing of actuators was required. Then, we have proposed a high aspect ratio coil lines for electromagnetic actuators in order to expect to reduce the size and increase the output power. To realize these coils and actuators, we have fabricated a three dimensional X-ray lithography and metallization process. Using these processes, we have formed three-dimensional coil lines with high aspect ratio that could be used in electromagnetic actuators. In this paper, we have fabricated coil lines with 10 mum line width, 20 mum pitch and aspect ratio of 5 on the surface of an acrylic pipe by mean of three-dimensional X-ray lithography technique. And, a void-free metallic deposit could be formed on a thin coil lines by electroplating method. It is very expected the high performance microcoils and actuators with high aspect ratio could be manufactured in spite of the miniature size.

Electrostatic Capacity Type Micro Inclination Sensor Utilizing Dielectric Nano-Particles

We have developed a capacitive inclination sensor 5 mm times 5 mm times 1.5 mm in size, with a linear analog output. The sensor has three features. First, a method is used that increases permittivity by mixing dielectric nanoparticles with dielectric oil. The resulting high permittivity facilitates sensor miniaturization and high performance. Second, the slit structure and the pseudo channel structure are used to reduce the effect of dielectric oil surface tension on the sensor. Third, direct bonding between electrode and resin is used to reduce dispersion in cavity volume. We succeeded in increasing permittivity by 50% by mixing, with dielectric oil, BaTiO3 nanoparticles 30 nm in diameter at a concentration of 15 Vol%. When evaluated, the sensor successfully produced a linear analog output within the range of -45 to +45 deg. Direct bonding using the hydrogen bond enabled electrode attachment to resin without adhesive. From the above results, we judge that it will probably be possible to manufacture a smaller inclination sensor equivalent to the conventional one

Optimization of Au mask fabrication processes for LIGA applications

This paper presents approaches to fabricate Au masks for LIGA process. The proposed fabrication process starts with deposition of a thick layer of Au film, then followed by electron cyclotron resonance (ECR) Ar+ etching and coating of a polymer material that is used as a membrane. Finally the ICP DRIE etching is applied from backside to figure out the membrane. The profiles of the Au microstructures on the mask have been improved thanks to the optimization of etching process and photoresist material. The fabricated masks have been used in the X-ray lithography and demonstrated a well acceptable performance. A nickel mold has been successfully realized by electroplating and used in a hot embossing process for forming optical components. Au masks made by using conventional Au-electroplating technique have also been demonstrated for a comparison.