2P-24 Analysis of surface wrinkling on multiple stacked metal/polymeric layer via free energy

유성수,유필진 한국공업화학회 2017 한국공업화학회 연구논문 초록집 Vol.2017 No.1

Surface wrinkling can be occurred when compressive stress in the film exceeds the critical stress, and there have been a number of researches on instability of wrinkling. Since most of electronic devices in nanoscale possess sequentially stacked layer structure, instability of surface wrinkling on multilayer can be significant tool for fabrication of electronic device. However, most of researches focus on wrinkling on bilayer, not for the wrinkling on multilayer. Therefore, instability of wrinkling on multilayer has been less investigated. In this research, we designed models for free energy analysis that can analyze multilayer wrinkling, and derived relationship between measurable parameter such as wavelength of wrinkled surface, elastic modulus, poisson’s ratio and thickness. In addition we introduced metrology that can overcome the limitation of conventional metrology based on bilayer wrinkling s application of this instability of multilayer wrinkling.

봉독이 피부 노화에 미치는 영향

김진명,김윤범,Kim, Jin-Myoung,Kim, Yoon-Bum 대한한방안이비인후피부과학회 2010 한방안이비인후피부과학회지 Vol.23 No.2

Background and Objective : Increasing interest in anti-aging and anti-wrinkling agents for the skin has triggered the recent outflow of researches and studies in this field. This study was designed to investigate the effects of bee venom on skin wrinkling and skin aging by testing the skin wrinkling, skin elasticity, trans-epidermal water loss (TEWL), free radical level, anti-oxidative agent level, and skin tissue after infusion of bee venom on hairless mouse. Materials and Methods : Fifteen hairless mice aged between 36~40 weeks were divided randomly into 3 Group; the Bee Venom Syringe Group, the Bee Venom Needle Group, and the control group. The Bee Venom Syringe Group were injected subcutaneously with bee venom (0.1cc in total) using an insulin syringe on three spots in the lumbar spine (one spot on the center and two spots 1~2cm to the side bilaterally). The Bee Venom Needle Group were pricked with bee venom-smeared acupuncture needles on three longitudinal spots in the lumbar spine each 1cm apart, after which the needles were removed 10 minutes later. The Control Group did not receive any form of intervention. All procedures took place thrice a week for four weeks, during which the mice were allowed free access to water and fodder. The mice were measured and compared in the weight, skin wrinkling scale, skin elasticity, and TEWL before and after the experiment. After the experiment, blood samples were taken to measure the free radical and anti-oxidative agent level, and the skin tissue was sliced for examination. Data was analyzed using the SPSS program (ver 12.0). The ANOVA analysis was used to compare and contrast the three groups, and t-test for paired samples was used to evaluate skin-wrinkling before and after experiment. The cut-off p-value of significance was set at p<0.05. Results : 1. Administration of bee venom did not cause serious weight loss or gain. 2. Compared to the control group, the Bee Venom Syringe Group and the Bee Venom Needle Group both showed a decrease in skin wrinkling scale after intervention. Especially, the Bee Venom Syringe Group showed a significant decrease (p<0.05). 3. Compared to the control group, the Bee Venom Syringe Group and the Bee Venom Needle Group both showed an increase in skin elasticity. Especially, the Bee Venom Syringe Group showed a significant increase (p<0.05). 4. No significant change in TEWL was found in the mice in all the three groups before and after experiment. 5. Free radical level was normal in all 15 mice in all the three groups, and anti-oxidative agent was not significantly different across the three groups. 6. The Bee Venom Syringe Group, the Bee Venom Needle Group, and the control group did not show any significant difference in the thickness of epidermis and dermis, infiltration of inflammatory cells, and skin wrinkling. The epidermis layer was relatively better preserved in the Bee Venom Syringe Group as compared to the Bee Venom Needle Group and the control group. Conclusion : Direct injection of bee venom on the hairless mouse using a syringe was found to improve wrinkling of the skin and increase skin elasticity but did not show effectiveness on skin dryness due to water loss. The bee venom appears to have suppressive effects on skin wrinkling, one of the symptoms of skin aging, through a process independent of suppression of free radicals or increase of anti-oxidative agent.

The effect of anisotropy on wrinkling of tube under rotary draw bending

Kourosh Hasanpour,Mahmoud Barati,Behnaz Amini,Mehrdad Poursina 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.3

Rotary draw tube bending is one of the most complex tube forming processes subject to different process parameters such as mate-rial properties and geometry. This process is being practiced in more and more applications in industry due to its high efficiency, high forming precision and quality. However, improper process parameters can lead to wrinkling which restrict the thin walled tube bending. Therefore, the prediction and prevention of wrinkling is very important. Despite its importance, the effect of anisotropy on the occurrence of wrinkling was not considered in the literature up to now. In this investigation, a quantitative study on the wrinkling of thin walled tube bending is carried out through a finite element model of the process using velocity integral parameter, which is used for the detection of wrinkles. The other methods usually warn the wrinkling initiation with no precise location prediction. In addition, the effects of some process parameters, specially normal and planar anisotropy on the tube wrinkling are investigated. It is shown that increasing normal and planar anisotropy (increasing r0 and r90 values) result in a decrease in tube wrinkling.

Fabrication of Complexly Patterned Wavy Structures Using Self-Organized Anisotropic Wrinkling

Pil J. Yoo 대한금속·재료학회 2011 ELECTRONIC MATERIALS LETTERS Vol.7 No.1

In this work, we review a novel means of self-organized anisotropic wrinkling, which enables the patterning of wavy microstructures that are rarely achievable with conventional patterning approaches. The surface wrinkling phenomenon usually occurs in a system of stacked layers in the course of relieving the accumulated stress therein. For example, the polymer/metal bilayer system supported on a rigid substrate can generate random wrinkles on the surface due to the compressive stress resulting from thermal annealing. However,these random and isotropic wrinkles can be self-organized and ordered by an external confinement effect being guided in periodic microstructures of a patterned mold material. By exploiting the competitive wave interactions between the intrinsic wrinkling wavelength and periodic spacing of the externally imposed mold,complex wavy structures can be created with designed shape of the wrinkles. In addition, manipulating the contact condition of the external mold can allow controllability over the phase of patterned wrinkles. Therefore,the proposed technique is anticipated to be useful in a broad range of applications in micro-optics, microfluidic devices, and flexible electronics.

Competitive concurrence of surface dewetting and wrinkling of liquid crystalline network films

송성은,최관현,유필진 한국공업화학회 2018 한국공업화학회 연구논문 초록집 Vol.2018 No.0

In this study, we propose polymeric thin films of liquid crystalline (LC) mesogens prepared on a non-wettable Si substrate and apply a treatment of plasma irradiation to form a thin polymerized layer at the surface. The resulting compressive stress generated in the surface region drives the formation of wrinkles, while at the same time, dipolar attraction between LC molecules induces competitive cohesive dewetting. Intriguing surface structures were obtained whereby dewettinglike hole arrays are nested inside the randomly propagated wrinkles. The structural features are readily controlled by the degree of surface cross-linking, hydrophilicity of the substrates, and the LC film thickness.

Self-Assembly of gold nano particles on templated patterns formed by wrinkling

김재겸,유필진 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.1

Surface-ordered nanoparticles were studied via template-guided selfassembly of spherical monodisperse gold nanoparticles in wrinkled templates. Surface instability and pattern formation based on difference in thermal expansion between bilayers was employed as a guidline for patterned particle assembly. Tuning the wrinkle`s wavelength enables us to precisely confirm the assembly morphology and fabricate line and complex nano-particles patterns. Furthermore, surface charge on wrinkles can be changed using different silica precursors. It helps to arrange gold nanoparticles in wrinkles or cover nano-colloids on wrinkled surface controlling electrostatic interaction between particles and surface. It is expected that highly regular 1- and 2-dimensional patterned nano gold colloids will be promising candidates for various applications such as sensors, surface enhanced raman spectroscopy, photovoltaics or plasmon enhanced solar cells.

Influence of specimen pre-shear and wrinkling on the accuracy of uniaxial bias extension test results

Alsayednoor, J.,Lennard, F.,Yu, W.R.,Harrison, P. Elsevier 2017 Composites Applied science and manufacturing Vol.101 No.-

<P><B>Abstract</B></P> <P>The influence of unintended specimen pre-shear and out-of-plane wrinkling on the accuracy of shear angle and axial force results, measured during a uniaxial bias extension (UBE) test on engineering fabrics, is examined. Three techniques of measuring test kinematics are investigated, including manual image analysis, 2-D and 3-D full-field analysis. Error introduced by specimen pre-shear is shown to influence test results in different ways, depending on analysis technique. Procedures to take specimen pre-shear error into account when interpreting results are demonstrated, though an important recommendation resulting from this investigation is to minimise pre-shear as much as possible. Out-of-plane wrinkling is shown to create significant errors in kinematic data when using 2-D analysis methods (up to 20% overestimates of measured shear angle). It is shown that wrinkle-error can be corrected if 3-D stereoscopic analysis methods are employed.</P>

인장 막 구조물에 발생하는 주름 해석 방법

김재열(Kim Jae-Yeol) 대한건축학회 2010 大韓建築學會論文集 : 構造系 Vol.26 No.3

The objective of the research are to formulate equations for wrinkling problem in tension membrane structures and to complete a program coding within existed stress-deformation analysis program. Two models, triangular model and rectangular model, are analyzed with the presented process and the results are compared with existed results to verify the validation of program. The results of two models shows good agreement. And also, this study investigated the effect of a small value called α which is related to the specification of stress-strain matrix in the numerical procedures on the outcome of stress analysis considering wrinkling. Several models are analyzed to investigate the effect of α and presented a proper range of α.

Process analysis of two-layered tube hydroforming with analytical and experimental verification

S. M. Hossein Seyedkashi,문영훈,Valiollah Panahizadeh R.,Haibin Xu,Sang-Yun Kim 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.1

Two-layered tubular joints are suitable for special applications. Designing and manufacturing of two layered components require enough knowledge about the tube material behavior during the hydroforming process. In this paper, hydroforming of two-layered tubes is investigated analytically, and the results are verified experimentally. The aim of this study is to derive an analytical model which can be used in the process design. Fundamental equations are written for both of the outer and inner tubes, and the total forming pressure is obtained from these equations. Hydroforming experiments are carried out on two different combinations of materials for inner and outer tubes; case 1: copper/aluminum and case 2: carbon steel/stainless steel. It is observed that experimental results are in good agreement with the theoretical model obtained for estimation of forming pressure able to avoid wrinkling.

An extremum method for bending-wrinkling predictions of inflated conical cantilever beam

Changguo Wang,Zhenyong Du,Huifeng Tan 국제구조공학회 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.46 No.1

An extremum method is presented to predict the wrinkling characteristics of the inflated cone in bending. The wrinkling factor is firstly defined so as to obtain the wrinkling condition. The initial wrinkling location is then determined by searching the maximum of the wrinkling factor. The critical wrinkling load is finally obtained by determining the ratio of the wrinkling moment versus the initial wrinkling location. The extremum method is proposed based on the assumption of membrane material of beam wall, and it is extended to consider beam wall with thin-shell material in the end. The nondimensional analyses show that the initial wrinkling location is closely related to the taper ratio. When the taper ratio is higher than the critical value, the initial wrinkles will be initiated at a different location. The nondimensional critical wrinkling load nonlinearly increases as the taper ratio increases firstly, and then linearly increases after the critical taper ratio. The critical taper ratio reflects the highest load-carrying efficiency of the inflated cone in bending, and it can be regarded as a measure to optimize the geometry of the inflated cone. The comparative analysis shows fairly good agreement between analytical and numerical results. Over the whole range of the comparison, the mean differences are lower than 3%. This gives confidence to use extremum method for bending-wrinkling analysis of inflated conical cantilever beam.