섬(Island) 구조로 이루어진 강성도 국부변환 신축성 기판의 변형 거동

오현아,박동현,신수진,오태성,Oh, Hyun-Ah,Park, Donghyeun,Shin, Soo Jin,Oh, Tae Sung 한국마이크로전자및패키징학회 2015 마이크로전자 및 패키징학회지 Vol.22 No.4

In order to develop stretchable substrate technology for stretchable devices, locally stiffness-variant stretchable substrates were processed with two polydimethylsiloxane elastomers of different stiffnesses and their deformation behavior was characterized. Low-stiffness substrate matrix and embedded high-stiffness island of the stretchable substrate were formed by using Dragon Skin 10 of the elastic modulus of 0.09 MPa and Sylgard 184 of the elastic modulus of 2.15 MPa, respectively. A stretchable substrate was fabricated to a configuration of 6.5 cm length, 0.4 cm thickness, and 2.5 cm width. The elastic modulus of a stretchable substrate was increased from 0.09 MPa to 0.13~0.33 MPa by embedding a Sylgard 184 island of 1 cm width and 1~6 cm length into the center part of the Dragon Skin 10 substrate matrix. The elastic modulus of a stretchable substrate was improved to 0.16~0.2 MPa by embedding a Sylgard 184 island of 4 cm length and 0.5~1.5 cm width and to 0.1421~0.154 MPa by embedding a Sylgard 184 island of 2 cm length and 0.5~1.5 cm width. With increasing the tensile strain of a stretchable substrate, deformation restriction of the locally stiffness-variant Sylgard 184 island was further enhanced due to substantial increase in the strength difference between Sylgard 184 and Dragon 10 at large strain. 신축성 디바이스용 강성도 국부변환 기판기술을 개발하기 위해 강성도가 서로 다른 두 polydimethylsiloxane 탄성고분자를 사용하여 섬(island) 구조로 이루어진 강성도 국부변환 신축성 기판을 형성하고 변형 거동을 분석하였다. 기판 기지로는 탄성계수가 0.09 MPa인 Dragon Skin 10을 사용하였으며, 섬 구조의 강성도 국부변환부는 탄성계수가 2.15 MPa인 Sylgard 184를 사용하였다. 신축성 기판의 형상은 길이 6.5 cm, 두께 0.4 cm, 폭 2.5 cm 이었다. Dragon Skin 10 기지에 폭 1 cm, 길이 1~6 cm인 Sylgard 184의 삽입에 의해 신축성 기판의 탄성계수가 0.09 MPa에서 0.13~0.33 MPa로 증가하였다. 길이 4 cm, 폭 0.5~1.5 cm인 Sylgard 184 강성도 국부변환부를 내재시킴에 따라 신축성 기판의 탄성계수가 0.16~0.2 MPa로 증가하였으며, 길이 2 cm, 폭 0.5~1.5 cm인 강성도 국부변환부를 내재시킴에 따라 탄성계수가 0.142~0.154 MPa로 증가하였다. 신축성 기판의 변형률이 증가함에 따라 Sylgard 184와 Dragon Skin 10의 강도 차이가 현저히 증가하는데 기인하여 강성도 국부변환부의 변형억제 효과가 향상되었다.

Effect of stiffness modulation on mechanical stability of stretchable a-IGZO TFTs

Park, Hyungjin,Cho, Kyoungah,Oh, Hyungon,Kim, Sangsig Elsevier 2018 Superlattices and microstructures Vol.117 No.-

<P><B>Abstract</B></P> <P>In this study, we fabricate the amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs) on a stretchable substrate with a buffer stage and investigate the mechanical stability and electrical characteristics when the length of the substrate is stretched by 1.7 times. The buffer stage is responsible for the stiffness modulation of the stretchable substrate. The mobility, the threshold voltage and the on/off ratio of the stretchable a-IGZO TFT are measured to be 18.1 cm<SUP>2</SUP>/V·s, 1 V, and 3 × 10<SUP>7</SUP>, respectively. Our simulation conducted by a three dimensional finite elements method reveals that the stiffness modulation reduces the stress experienced by the substrate in the stretched state by about one-tenth. In addition, the mechanical stability and electrical characteristics of the a-IGZO TFT are maintained even when the substrate is stretched by 1.7 times.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We fabricate an a-IGZO TFT on a stretchable substrate with a buffer stage. </LI> <LI> The buffer stage results in the stiffness modulation of the stretchable substrate. </LI> <LI> The distribution of stress and strain about the substrate is analyzed by simulator. </LI> </UL> </P>

신축성 전자패키징용 강성도 국부변환 polydimethylsiloxane 기판의 탄성계수

오현아,박동현,한기선,오태성,Oh, Hyun-Ah,Park, Donghyeun,Han, Kee-Sun,Oh, Tae Sung 한국마이크로전자및패키징학회 2015 마이크로전자 및 패키징학회지 Vol.22 No.4

In order to apply to stretchable electronics packaging, locally stiffness-variant stretchable substrates consisting of island structure were fabricated by combining two polydimethylsiloxane elastomers of different stiffnesses and their elastic moduli were characterized as a function of the width of the high-stiffness island. The low-stiffness substrate matrix and the embedded high-stiffness island of the stretchable substrate were formed by using Dragon Skin 10 of the elastic modulus of 0.09 MPa and Sylgard 184 of the elastic modulus of 2.15 MPa, respectively. A stretchable substrate was fabricated to be a configuration of 6.5-cm length, 0.4-cm thickness, and 2.5-cm width, in which a high-stiffness Sylgard 184 island, of 4-cm length, 0.2-cm thickness, and 0.5~1.5-cm width, was embedded. The elastic modulus of a stretchable substrate was increased from 0.09 MPa to 0.16 MPa by incorporating the Sylgard 184 island of 0.5-cm width to Dragon Skin 10 substrate matrix. The elastic modulus was further improved to 0.18 MPa and 0.2 MPa with increasing the Sylgard 184 island width to 1.0 cm and 1.5 cm, which were in good agreement with values estimated by combining the Voigt structure of isostrain and the Reuss structure of isostress. 신축성 전자패키징에 응용하기 위해 강성도가 서로 다른 polydimethylsiloxane 탄성고분자인 Sylgard 184와 Dragon Skin 10을 사용하여 섬(island) 구조가 삽입된 강성도 국부변환 신축성 기판을 형성한 후, 강성도 국부변환부의 폭에 따른 기판의 탄성계수를 분석하였다. 기판 기지로는 탄성계수가 0.09 MPa인 Dragon Skin 10을 사용하였으며, 기판 기지 내에 삽입되는 강성도 국부변환부는 탄성계수가 2.15 MPa인 Sylgard 184로 형성하였다. 신축성 기판의 형상은 길이 6.5 cm, 두께 0.4 cm, 폭 2.5 cm이었으며, 중앙부에 길이 4 cm, 두께 0.2 cm, 폭 0.5~1.5 cm인 강성도 국부변환부를 삽입하였다. 폭 0.5 cm의 Sylgard 184를 Dragon Skin 10에 삽입함에 따라 기판의 탄성계수가 0.09 MPa에서 0.16 MPa로 증가하였다. Sylgard 184의 폭을 1.0 cm 및 1.5 cm으로 증가시킴에 따라 기판의 탄성계수가 0.18 MPa와 0.2 MPa로 증가하였으며, Sylgard 184 강성도 국부변환부의 폭에 따른 기판 탄성계수의 변화는 등변형률의 Voigt 구조와 등응력의 Reuss 구조를 조합하여 예측한 값과 잘 일치하였다.

Combined Effects of Substrate Topography and Stiffness on Endothelial Cytokine and Chemokine Secretion

Jeon, Hyeona,Tsui, Jonathan H.,Jang, Sue Im,Lee, Justin H.,Park, Soojin,Mun, Kevin,Boo, Yong Chool,Kim, Deok-Ho American Chemical Society 2015 ACS APPLIED MATERIALS & INTERFACES Vol.7 No.8

<P>Endothelial physiology is regulated not only by humoral factors, but also by mechanical factors such as fluid shear stress and the underlying cellular matrix microenvironment. The purpose of the present study was to examine the effects of matrix topographical cues on the endothelial secretion of cytokines/chemokines in vitro. Human endothelial cells were cultured on nanopatterned polymeric substrates with different ratios of ridge to groove widths (1:1, 1:2, and 1:5) and with different stiffnesses (6.7 MPa and 2.5 GPa) in the presence and absence of 1.0 ng/mL TNF-α. The levels of cytokines/chemokines secreted into the conditioned media were analyzed with a multiplexed bead-based sandwich immunoassay. Of the nanopatterns tested, the 1:1 and 1:2 type patterns were found to induce the greatest degree of endothelial cell elongation and directional alignment. The 1:2 type nanopatterns lowered the secretion of inflammatory cytokines such as IL-1β, IL-3, and MCP-1, compared to unpatterned substrates. Additionally, of the two polymers tested, it was found that the stiffer substrate resulted in significant decreases in the secretion of IL-3 and MCP-1. These results suggest that substrates with specific extracellular nanotopographical cues or stiffnesses may provide anti-atherogenic effects like those seen with laminar shear stresses by suppressing the endothelial secretion of cytokines and chemokines involved in vascular inflammation and remodeling.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2015/aamick.2015.7.issue-8/acsami.5b00554/production/images/medium/am-2015-00554x_0009.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am5b00554'>ACS Electronic Supporting Info</A></P>

다공성 매질 표면에서 박테리아의 거동

조명옥(Myoung-Ock Cho),조지용(Ji-Yong Cho),박은정(Eun-Jung Park),이동희(Dong Hee Lee),이정훈(Jeonghoon Lee),김중경(Jung Kyung Kim) 한국가시화정보학회 2008 한국가시화정보학회 학술발표대회 논문집 Vol.- No.2

It has been found that the colony size of bacteria grown on agar plate decreases with increasing agar gel concentration. Evidences from recent studies suggest that the bacterial colony dynamics is closely related with the mechanical properties of the substrate. We investigate whether bacterial growth on the agar substrate is controlled mostly by nutrients diffusion which is hindered more in porous medium than in solution. The number of bacterial cells in single colonies is found to be inversely correlated with agar concentration. High-resolution live cell imaging at the single bacterium level confirms that the bacterial growth rate is reduced with increasing agar concentration. There is a strong correlation between the slowed diffusion and the reduced number of cells in a high concentration of agar medium.

다공성 매질 표면에서 박테리아의 거동 : 확산의 영향

조명옥(Myoung-Ock Cho),조지용(Jiyong Cho),박은정(Eun-Jung Park),이동희(Donghee Lee),이정훈(Jeonghoon Lee),김중경(Jung Kyung Kim) 한국가시화정보학회 2008 한국가시화정보학회지 Vol.6 No.2

It has been found that the colony size of bacteria grown on an agar plate decreases with increasing agar gel concentration. Evidenc from recent studies suggests that the bacterial colony dynamics is closely related with the mechanical properties of the substrate. We investigate whether bacterial growth on the agar substrate is controlled mostly by the nutrients' diffusion which is hindered more in porous medium than in solution. The number of bacterial cells in single colonies is found to be inversely correlated with agar concentration. High-resolution live cell imaging at the single bacterium level confirms that the bacterial growth rate is reduced with increasing agar concentration. There is a strong correlation between the slowed diffusion and the reduced number of cells in a high concentration of agar medium.

세포기질의 강성이 전단응력으로 유도된 혈관내피세포 운동성에 미치는 영향에 대한 연구

송석현(Sukhyun Song),김미나(Mina Kim),김현유(Hyeonyu Kim),신현정(Jennifer H. Shin) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11

Vascular endothelial cell (VEC) forms a monolayer on the smooth muscle cell layer of blood vessel. Thus, substrate stiffness should be considered as one of the most important element in mimicking the physiological condition of VECs. In this research, the effect of substrate stiffness on shear stress induced cellular motility was investigated. VECs are seeded on polydimethylsiloxane (PDMS) substrate with controlled stiffness, ranging from 1.78 ㎫ to 48 ㎪. Shear stress system based on parallel plate flow chamber is utilized to apply laminar shear stress of 15 dyne/㎠. In order to explain the detailed mechanism of cellular migration, expression and distribution of cytoskeleton related pathway consisting RhoA, Rac1 and Cdc42 are examined. In addition, the regulation of syndecan-4 is observed as a mechanoreceptor. Results reveal that there is an optimal stiffness in maximizing the cell motility.

A modified elastic contact stiffness model considering the deformation of bulk substrate

Ling Li,Jingjing Wang,Xiyong Pei,Wei Chu,Anjiang Cai 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.2

Establishing an accurate and effective stiffness model of the elastic contact surface is the basis for further modeling and analysis of machine tool dynamics. In this paper, a new elastic contact stiffness model is proposed that considers the bulk substrate deformation and modifies the Greenwood and Williamson microcontact model (GW model) of rough surfaces. Based on the Hertz contact theory and fixed-point iteration method, a single asperity contact model is created to analyze the effects of bulk substrate deformation and coating materials. To make the contact stiffness model more accurate and effective, two aspects are improved: One is to introduce the triangular distribution function to make the asperity heights distribution more consistent with the actual machined surface, and the other is to correct the defects in the micro-contact process. Comparing the finite element simulation results with the modal test data, the correctness of the proposed contact stiffness model is verified. The simulation results reveal the influence of distribution function, surface roughness and coating material on the contact characteristics of the joint surface.

Substrate Stiffness Modulation of Morpho-Physical Traits and Pluripotency in iPSCs

Young-woo Jeon(전영우),Hoewon Park(박회원),Hyuntae Jeong(정현태),Namji Sung(성남지),Ki-Jun Yoon(윤기준),Jennifer H. Shin(신현정) 대한기계학회 2024 대한기계학회 춘추학술대회 Vol.2024 No.4

The effects of substrate stiffness and magnitude of hydrostatic pressure on osteogenic differentiation of MSCs

S. Y. Kim,J. S. Hyun,J. W. Shin,S. H. Park,Y. G. Kang,K. J. Jeon,J. W. Shin 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.3