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9. Large aperture MEMS mirror with integrated piezoelectric actuator

Author

Gary Li, Sergio F. M. Almeida, Wang Yufeng, Youmin Wang, Qin Zhou, and Lee Sae Won

Subjects
Microelectromechanical systems, Optics, Materials science, business.industry, Aperture, Moment of inertia, Deformation (meteorology), business, Rotation, Piezoelectricity, Collimated light, Voltage
Abstract

MEMS micromirror is playing more important roles in various applications. To increase the detection range and field-ofview (FOV), bigger aperture size with larger rotation angle (θopt⋅D) is always preferred. However, it comes with the cost of worse collimation performance due to larger dynamic deformation. A backside rib support design can be added to the mirror which can reduce dynamic deformation while keeping rotational inertia of moment low. Meanwhile, integrated piezoelectric actuator can be adopted to provide large driving force and to increase the rotation angle. In this paper, we demonstrate a MEMS micromirror actuated by integrated PZT thin film, with a large aperture size of 12mm×18mm and resonant frequency of 1.65 kHz can achieve 4.8° optical angle under 20 Vpp driving voltage. Design rules are deduced from the theoretical analysis to improve the performance of piezoelectric-actuated MEMS mirror.

Published
2021

17. SSeCKS regulates angiogenesis and tight junction formation in blood-brain barrier

Author

Lee, Sae-Won, Kim, Woo Jean, Choi, Yoon Kyung, Song, Hyun Seok, Son, Myung Jin, Gelman, Irwin H., Kim, Yung-Jin, and Kim, Kyu-Won

Abstract

The blood-brain barrier (BBB) is essential for maintaining brain homeostasis and low permeability. BBB maintenance is important in the central nervous system (CNS) because disruption of the BBB may contribute to many brain disorders, including Alzheimer disease and ischemic stroke. The molecular mechanisms of BBB development remain ill-defined, however. Here we report that src-suppressed C-kinase substrate (SSeCKS) decreases the expression of vascular endothelial growth factor (VEGF) through AP-1 reduction and stimulates expression of angiopoietin-1 (Ang-1), an antipermeability factor in astrocytes. Conditioned media from SSeCKS-overexpressing astrocytes (SSeCKS-CM) blocked angiogenesis in vivo and in vitro. Moreover, SSeCKS-CM increased tight junction proteins in endothelial cells, consequently decreasing [[sup.3]H]sucrose permeability. Furthermore, immunoreactivity to SSeCKS gradually increased during the BBB maturation period, and SSeCKS-expressing astrocytes closely interacted with zonula occludens (ZO)-1-expressing blood vessels in vivo. Collectively, our results suggest that SSeCKS regulates BBB differentiation by modulating both brain angiogenesis and tight junction formation., Author(s): Sae-Won Lee [1, 2, 4]; Woo Jean Kim [1, 2, 4]; Yoon Kyung Choi [1]; Hyun Seok Song [1, 2]; Myung Jin Son [1, 2]; Irwin H. Gelman [3]; [...]

Published
2003
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19. Histone deacetylases induce angiogenesis by negative regulation of tumor suppressor genes

Author

Kim, Myoung Sook, Kwon, Ho Jeong, Lee, You Mie, Baek, Jin Hyen, Jang, Jae-Eun, Lee, Sae-Won, Moon, Eun-Joung, Kim, Hae-Sun, Lee, Seok-Ki, Chung, Hae Young, Kim, Chul Woo, and Kim, Kyu-Won

Abstract

Low oxygen tension influences tumor progression by enhancing angiogenesis; and histone deacetylases (HDAC) are implicated in alteration of chromatin assembly and tumorigenesis. Here we show induction of HDAC under hypoxia and elucidate a role for HDAC in the regulation of hypoxia-induced angiogenesis. Overexpressed wild-type HDAC1 downregulated expression of p53 and von Hippel-Lindau tumor suppressor genes and stimulated angiogenesis of human endothelial cells. A specific HDAC inhibitor, trichostatin A (TSA), upregulated p53 and von Hippel-Lindau expression and downregulated hypoxia-inducible factor-1[alpha] and vascular endothelial growth factor. TSA also blocked angiogenesis in vitro and in vivo. TSA specifically inhibited hypoxia-induced angiogenesis in the Lewis lung carcinoma model. These results indicate that hypoxia enhances HDAC function and that HDAC is closely involved in angiogenesis through suppression of hypoxia-responsive tumor suppressor genes., Author(s): Myoung Sook Kim [1]; Ho Jeong Kwon [3]; You Mie Lee [1]; Jin Hyen Baek [1]; Jae-Eun Jang [1]; Sae-Won Lee [1]; Eun-Joung Moon [1]; Hae-Sun Kim [1]; Seok-Ki [...]

Published
2001
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27. The impact of e-HR on professional competence in HRM: Implications for the development of HR professionals.

Author

Bell, Bradford S., Lee, Sae-Won, and Yeung, Sarah K.

Subjects
INFORMATION technology, HUMAN capital, PERSONNEL management, COMPUTER science, EMPLOYEE reviews, PROFESSIONAL competence
Abstract

Information technology has been cited as a critical driver of HR's transition from a focus on administrative tasks to a focus on serving as a strategic business partner. This strategic role not only adds a valuable dimension to the HR function, but also changes the competencies that define the success of HR professionals. Interviews were conducted with HR representatives from 19 firms to examine the linkage between electronic human resources (e-HR) and the reshaping of professional competence in HRM. Based on the findings, we draw implications for the development of HR competencies and identify learning strategies that HR professionals can utilize to fulfill their changing roles and responsibilities. © 2006 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Published
2006
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30. Histological and functional assessment of the efficacy of constraint-induced movement therapy in rats following neonatal hypoxic-ischemic brain injury

Author

Kim, Hyunha, primary, Kim, Min Jae, additional, Koo, Young Soo, additional, Lee, Hae In, additional, Lee, Sae-Won, additional, Shin, Myung Jun, additional, Kim, Soo-Yeon, additional, Shin, Yong Beom, additional, Shin, Yong-Il, additional, Choi, Byung Tae, additional, Yun, Young Ju, additional, and Shin, Hwa Kyoung, additional

Published
2017
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33. The Short Isoform of DNAJB6 Protects against 1-Methyl-4-phenylpridinium Ion-Induced Apoptosis in LN18 Cells via Inhibiting Both ROS Formation and Mitochondrial Membrane Potential Loss

Author

Hong, Yeon-Mi, primary, Hong, Yohan, additional, Choi, Yeong-Gon, additional, Yeo, Sujung, additional, Jin, Soo Hee, additional, Lee, Sae-Won, additional, Sung, Backil, additional, Lee, Sook-Hyun, additional, Jung, Hyejin, additional, and Lim, Sabina, additional

Published
2017
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38. Development of a MEMS fabrication process for self-assembly of on-chip antennas

Author

Lee, Sae Won

Abstract

This thesis describes the development of a fabrication process for building efficient 60 GHz on-chip antennas. Using a polymer micromachining process, a self-assembly method was developed to vertically raise the antennas. Vertical on-chip antennas can offer higher efficiency compared to planar antennas. The self-assembly method provides flexibility to create three-dimensional structures with different shapes. The curl and the direction of self-assembled curved structures can be controlled with simple changes in the design layout. The fabrication process uses SU-8 polymer and the antennas are fabricated by coating the self-assembled polymer structures with metal. Micromachining using polymers is inexpensive, fast, and useful for a CMOS compatible MEMS fabrication process because most processing steps do not involve very high processing temperatures. This fabrication process can be completed within a day using university-level cleanroom equipment. This fast turnaround time makes the fabrication process ideal for prototyping antennas and other three-dimensional MEMS devices. Several fabrication processes were developed and tested during the research. Many of the advances focused on making efficient on-chip antennas while keeping the cost and time for fabrication low by using the polymer micromachining. A thick dielectric layer of SU-8 was used to increase the efficiency of the antennas by increasing the spacing between the more lossy CMOS substrate and the metallic antennas. The associated transmission lines were fabricated on the dielectric layer with a patterned metal layer. The self-assembled SU-8 antenna structures were coated by metal layers on each side to cover the whole antenna structures with an even thickness.

Published
2012

42. Designed angiopoietin-1 variant, COMP-angiopoietin-1, rescues erectile function through healthy cavernous angiogenesis in a hypercholesterolemic mouse

Author

Ryu, Ji-Kan, primary, Kim, Woo Jean, additional, Koh, Young Jun, additional, Piao, Shuguang, additional, Jin, Hai-Rong, additional, Lee, Sae-Won, additional, Choi, Min Ji, additional, Shin, Hwa-Yean, additional, Kwon, Mi-Hye, additional, Jung, Keehoon, additional, Koh, Gou Young, additional, and Suh, Jun-Kyu, additional

Published
2015
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43. Development and characterization of self-assembly using residual stress in a multi-user polymer MEMS process

Author

Lee, Sae-Won

Abstract

A novel self-assembly method is presented for creating self-assembled three-dimensional micro-electro-mechanical systems (MEMS) structures. The residual stress between structural polymer layers caused by separate curing processes has been used as the self-assembly mechanism. Various radii of curvature are presented using this self-assembly method in order to show the capability of fabricating three-dimensional microstructures. SU-8 negative photoresist is used as a structural material, and induced stresses are lithographically defined for self-assembly. The self-assembly mechanism is simulated using finite element analysis in ANSYS. Several types of self-assembled microstructures are presented. The fabrication is performed at low temperatures and is compatible with commercial integrated-circuit processes.

Published
2008

44. Prompt meningeal reconstruction mediated by oxygen-sensitive AKAP12 scaffolding protein after central nervous system injury

Author

Cha, Jong-Ho, primary, Wee, Hee-Jun, additional, Seo, Ji Hae, additional, Ju Ahn, Bum, additional, Park, Ji-Hyeon, additional, Yang, Jun-Mo, additional, Lee, Sae-Won, additional, Lee, Ok-Hee, additional, Lee, Hyo-Jong, additional, Gelman, Irwin H., additional, Arai, Ken, additional, Lo, Eng H., additional, and Kim, Kyu-Won, additional

Published
2014
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47. AKAP12 Mediates Barrier Functions of Fibrotic Scars during CNS Repair

Author

Cha, Jong-Ho, primary, Wee, Hee-Jun, additional, Seo, Ji Hae, additional, Ahn, Bum Ju, additional, Park, Ji-Hyeon, additional, Yang, Jun-Mo, additional, Lee, Sae-Won, additional, Kim, Eun Hee, additional, Lee, Ok-Hee, additional, Heo, Ji Hoe, additional, Lee, Hyo-Jong, additional, Gelman, Irwin H., additional, Arai, Ken, additional, Lo, Eng H., additional, and Kim, Kyu-Won, additional

Published
2014
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