Powder injection molding process for fabrication of piezoelectric 2D array ultrasound transducer

Han, Ji-Sheng; Gal, Chang Woo; Park, Jae Man; Kim, Jong Hyun; Lee, Seung Hee; Yeo, Bong Whan; Lee, Baik Woo; Park, Sung Sik; Park, Seong Jin

doi:10.1088/1361-665x/aab27c

Cited by 11 publications

(3 citation statements)

References 17 publications

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“…Judging from the results, it is expected that the gold layer can perfectly block the X-ray during the exposure process. In general, dose states on both the absorber and PMMA are recommended to form a defect-free mother structure under four conditions [25]. 1The dose on the absorber top should be lower than 100 J/cm 3 to avoid development.…”

Section: Metal Electroformingmentioning

confidence: 99%

Microfabrication of Ni-Fe Mold Insert via Hard X-ray Lithography and Electroforming Process

Park

Shin

et al. 2020

Metals

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In this research, a Ni-Fe mold insert for the efficient replication of high aspect-ratio microstructure arrays was fabricated via hard X-ray lithography and an electroforming process. For the X-ray exposure on a photoresist, a gold-based X-ray mask was prepared with conventional UV photolithography. The gold thickness was designed to be over 15 μm to prevent development underneath the absorber and to enhance the adhesion strength between the photoresist and substrate. By using the X-ray mask, a positive-type photoresist was selectively exposed to X-ray under an exposure energy of 4 kJ/cm3. Thereafter, the exposed region was developed in a downward direction to effectively remove the residual photoresist from the substrate. During the evaporation process, deionized water mixed with a surface additive prevented the bending and clustering of the photoresist microstructure arrays by lowering the capillary force, resulting in a defect-free mother structure for electroforming. Lastly, the mother structure was uniformly Ni-Fe electroformed on a conductive substrate without the formation of any pores or detachment from the substrate. Based on the proposed microfabrication process, a Ni-Fe mold insert with a 183 μm pattern size, 68 μm gap size, 550 μm height, 2116 microcavities and a hardness of 585 Hv was precisely manufactured. It can be utilized for the mass production of high aspect ratio metal and ceramic microstructure arrays in micro molding technologies.

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Section: Metal Electroformingmentioning

confidence: 99%

Microfabrication of Ni-Fe Mold Insert via Hard X-ray Lithography and Electroforming Process

Park

Shin

et al. 2020

Metals

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“…Similarly, three-dimensional ultrasound images can be obtained either using a single transducer and performing mechanical scans along two orthogonal directions or using a linear array and performing a single mechanical scan. Another possibility relies in the use of 2D transducer arrays, which however imply severe technological challenges [30,31].…”

Section: Fundamentals Of Ultrasonicsmentioning

confidence: 99%

Ultrasound Systems for Biometric Recognition

Iula

2019

Sensors

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Biometric recognition systems are finding applications in more and more civilian fields because they proved to be reliable and accurate. Among the other technologies, ultrasound has the main merit of acquiring 3D images, which allows it to provide more distinctive features and gives it a high resistance to spoof attacks. This work reviews main research activities devoted to the study and development of ultrasound sensors and systems for biometric recognition purposes. Several transducer technologies and different ultrasound techniques have been experimented on for imaging biometric characteristics like fingerprints, hand vein pattern, palmprint, and hand geometry. In the paper, basic concepts on ultrasound imaging techniques and technologies are briefly recalled and, subsequently, research studies are classified according to the kind of technique used for collecting the ultrasound image. Overall, the overview demonstrates that ultrasound may compete with other technologies in the expanding market of biometrics, as the different commercial fingerprint sensors integrated in portable electronic devices like smartphones or tablets demonstrate.

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“…The same reasoning holds for 3D ultrasound images; they can be collected by moving a single element transducer along two orthogonal directions, by moving a linear ultrasonic array along its elevation direction only, or by using a 2D array of transducers, which performs electronic scans along the two directions. This last approach would certainly be the most desirable, yet it involves difficult technological problems [31]. On the other hand, a single transducer may be used only when the scanning area is relatively narrow [11].…”

Section: Ultrasound Imagingmentioning

confidence: 99%

Experimental Validation of a Reliable Palmprint Recognition System Based on 2D Ultrasound Images

Iula

Micucci

2019

Electronics

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Ultrasound has been trialed in biometric recognition systems for many years, and at present different types of ultrasound fingerprint readers are being produced and integrated in portable devices. An important merit of the ultrasound is its ability to image the internal structure of the hand, which can guarantee improved recognition rates and resistance to spoofing attacks. In addition, ambient noise like changes of illumination, humidity, or temperature, as well as oil or ink stains on the skin do not affect the ultrasound image. In this work, a palmprint recognition system based on ultrasound images is proposed and experimentally validated. The system uses a gel pad to obtain acoustic coupling between the ultrasound probe and the user’s hand. The collected volumetric image is processed to extract 2D palmprints at various under-skin depths. Features are extracted from one of these 2D palmprints using a line-based procedure. Recognition performances of the proposed system were evaluated by performing both verification and identification experiments on a home-made database containing 281 samples collected from 32 different volunteers. An equal error rate of 0.38% and an identification rate of 100% were achieved. These results are very satisfactory, even if obtained with a relatively small database. A discussion on the causes of bad acquisitions is also presented, and a possible solution to further optimize the acquisition system is suggested.

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Powder injection molding process for fabrication of piezoelectric 2D array ultrasound transducer

Cited by 11 publications

References 17 publications

Microfabrication of Ni-Fe Mold Insert via Hard X-ray Lithography and Electroforming Process

Microfabrication of Ni-Fe Mold Insert via Hard X-ray Lithography and Electroforming Process

Ultrasound Systems for Biometric Recognition

Experimental Validation of a Reliable Palmprint Recognition System Based on 2D Ultrasound Images

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