Rheological evaluation of petroleum jelly as a base material in ointmentand cream formulations with respect to rubbing onto the human body

Eun-Kyoung Park,Ki-Won Song,Ki-Won Song 한국유변학회 2010 Korea-Australia rheology journal Vol.22 No.4

The objective of the present study is to systematically characterize a nonlinear viscoelastic behavior of petroleum jelly in large amplitude oscillatory shear flow fields correspondent to the rubbing condition onto the human body. With this aim, using a strain-controlled rheometer, the dynamic viscoelastic properties of commercially available petroleum jelly have been measured at 37oC (body temperature) over a wide range of strain amplitudes at several fixed angular frequencies. In this article, the strain amplitude dependence of the dynamic viscoelastic behavior was firstly reported in detail from the experimentally obtained data and then the results were explained from a structural view-point of petroleum jelly. Nextly, a comparison of elastic and viscous properties was made in small and large strain amplitude ranges and then these results were discussed in depth with a special emphasis on their importance in actual usage situations (i.e., rubbing onto the human body or skin). Main findings obtained from this study can be summarized as follows : (1) Both the storage modulus and loss modulus show a linear behavior only within an extremely small strain amplitude range (g0<0.2%) and exhibit almost an equivalent strain limit of linear response (gEL≈gVL≈0.2 %). (2) Both the storage modulus and loss modulus demonstrate a qualitatively similar strain-dependent nonlinear behavior (i.e., strain-thinning feature), even though the storage modulus shows a stronger dependence on strain amplitude than does the loss modulus. (3) As the strain amplitude is increased, the difference between the storage modulus and loss modulus is gradually decreased and subsequently a viscous property becomes superior to an elastic property at sufficiently large strain amplitude range. (4) A large amplitude oscillatory shear flow behavior can provide a plentiful information for a better understanding of the complicated rheological behavior of semi-solid ointment-like materials in their actual application onto the human body or skin.

감육배관의 저주기 피로 평가를 위한 국부 탄소성 변형률 평가 방법

윤기봉(Kee Bong Yoon),마영화(Young Wha Ma),안중혁(Joong Hyok An),김윤재(Yun Jae Kim) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6

In order to assess the integrity of pipes with local thinning area, the plastic strain as well as the elastic strain at the root of thinned region are required particularly when fluctuating load is applied to the pipe. For estimating elastic-plastic strain at local wall thinning area in a straight pipe under tensile load, an estimation model with idealized fully circumferential constant depth wall thinning area is proposed. Based on the compatibility and equilibrium equations a nonlinear estimation equation, from which local elastic-plastic strain can be determined as a function of pipe/defect geometry, material and the applied strain was derived. Estimation results are compared with those from detailed elastic-plastic finite element analysis, which shows good agreements. Noting that practical wall thinning in nuclear piping has not only a circular shape but also a finite circumferential length, the proposed solution for the ideal geometry is extended based on two-dimensional and three-dimensional numerical analysis of pipes with circular wall thinning.

강성도 국부 변환 신축성 기판 위에 제작된 박막 트랜지스터 기반 변형률 센서

조영민,류경인,정성준 한국센서학회 2023 센서학회지 Vol.32 No.6

Stiffness-engineered stretchable substrate technology has been widely used to produce stretchable displays, transistors, and integratedcircuits because it is compatible with various flexible electronics technologies. However, the stiffness-engineering technology has neverbeen applied to transistor-based stretchable strain sensors. In this study, we developed thin-film transistor-based strain sensors on stiffness-engineered stretchable substrates. We designed and fabricated strain-sensitive stretchable resistors capable of inducing changes indrain currents of transistors when subjected to stretching forces. The resistors and source electrodes of the transistors were connectedin series to integrate the developed stretchable resistors with thin-film transistors on stretchable substrates by printing the resistors afterfabricating transistors. The thin-film transistor-based stretchable strain sensors demonstrate feasibility as strain sensors operating understrains of 0%–5%. This strain range can be extended with further investigations. The proposed stiffness-engineering approach willexpand the potential for the advancement and manufacturing of innovative stretchable strain sensors.

Mechanical strain-induced defect states in amorphous silicon channel layers of thin-film transistors

Kim, M.,Oh, H.,Park, S.,Cho, K.,Kim, S. Elsevier Sequoia 2017 THIN SOLID FILMS - Vol.641 No.-

In this study, we examined mechanical strain-induced defect states in hydrogenated amorphous silicon (a-Si:H) channel layers of thin-film transistors (TFTs) bent with a curvature radius of 18mm. When strain is applied to the TFTs, our devices feature strain-induced variations in threshold voltage (~1.47V), subthreshold swing (~0.36V/dec), and field-effect mobility (~0.031cm<SUP>2</SUP>V<SUP>-1</SUP>s<SUP>-1</SUP>). The electrical characteristics of a-Si:H TFTs on bendable substrates under mechanical strain are explained by the variation in the density of states (DOS) of defects in the channel layers. Our simulation work on the DOS in the a-Si:H channel layers under mechanical strain reveals that the mechanical strain causes not only the deformation of the density of mid-gap defect states but also an increase in the band-tail states within the band gap.

In situ reduction of gold nanoparticles in PDMS matrices and applications for large strain sensing

Donghyeon Ryu,Kenneth J. Loh,Robert Ireland,Mohammad Karimzada,Frank Yaghmaie,Andrea M. Gusman 국제구조공학회 2011 Smart Structures and Systems, An International Jou Vol.8 No.5

Various types of strain sensors have been developed and widely used in the field for monitoring the mechanical deformation of structures. However, conventional strain sensors are not suited for measuring large strains associated with impact damage and local crack propagation. In addition, strain sensors are resistive-type transducers, which mean that the sensors require an external electrical or power source. In this study, a gold nanoparticle (GNP)-based polymer composite is proposed for large strain sensing. Fabrication of the composites relies on a novel and simple in situ GNP reduction technique that is performed directly within the elastomeric poly(dimethyl siloxane) (PDMS) matrix. First, the reducing and stabilizing capacities of PDMS constituents and mixtures are evaluated via visual observation, ultraviolet-visible (UV-Vis) spectroscopy, and transmission electron microscopy. The large strain sensing capacity of the GNP-PDMS thin film is then validated by correlating changes in thin film optical properties (e.g., maximum UV-Vis light absorption) with applied tensile strains. Also, the composite’s strain sensing performance (e.g., sensitivity and sensing range) is also characterized with respect to gold chloride concentrations within the PDMS mixture.

Effect of mesopore-induced strain/stress on the thermoelectric properties of mesoporous ZnO thin films

Hong, Min-Hee,Shim, Dong Il,Cho, Hyung Hee,Park, Hyung-Ho Elsevier 2018 APPLIED SURFACE SCIENCE - Vol.446 No.-

<P><B>Abstract</B></P> <P>In present study, induced strain and stress effect of mesoporous structure on the thermoelectric properties of ZnO thin films were systematically investigated. In this work, mesoporous ZnO thin films were synthesized by evaporation-induced self-assembly and sol-gel process. As the pore structure is formed, the grain growth of ZnO is inhibited and lattice distortion is induced. In this paper, strain/stress induction according to surfactant (Brij-S10) concentration was analyzed through Williamson-Hall analysis. And the relationship between strain induction and thermoelectric properties was studied. 0.07 M ratio of Brij-S10 to Zn induces the enhanced thermoelectric properties as compared with pristine ZnO thin films. Hence, the induced strain and stress could play an important role in enhancing the thermoelectric properties of mesoporous ZnO thin films.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Synthesis of mesoporous ZnO thin films using evaporation-induced self-assembly process. </LI> <LI> XRD peak was broadened as increased surfactant concentration. </LI> <LI> Induced strain, stress, and energy density was calculated by using Williamson-Hall analysis. </LI> <LI> Improved thermoelectric property followed by mesoporous structure and tensile strain. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

In situ reduction of gold nanoparticles in PDMS matrices and applications for large strain sensing

Ryu, Donghyeon,Loh, Kenneth J.,Ireland, Robert,Karimzada, Mohammad,Yaghmaie, Frank,Gusman, Andrea M. Techno-Press 2011 Smart Structures and Systems, An International Jou Vol.8 No.5

Various types of strain sensors have been developed and widely used in the field for monitoring the mechanical deformation of structures. However, conventional strain sensors are not suited for measuring large strains associated with impact damage and local crack propagation. In addition, strain sensors are resistive-type transducers, which mean that the sensors require an external electrical or power source. In this study, a gold nanoparticle (GNP)-based polymer composite is proposed for large strain sensing. Fabrication of the composites relies on a novel and simple in situ GNP reduction technique that is performed directly within the elastomeric poly(dimethyl siloxane) (PDMS) matrix. First, the reducing and stabilizing capacities of PDMS constituents and mixtures are evaluated via visual observation, ultraviolet-visible (UV-Vis) spectroscopy, and transmission electron microscopy. The large strain sensing capacity of the GNP-PDMS thin film is then validated by correlating changes in thin film optical properties (e.g., maximum UV-Vis light absorption) with applied tensile strains. Also, the composite's strain sensing performance (e.g., sensitivity and sensing range) is also characterized with respect to gold chloride concentrations within the PDMS mixture.

Observation of fault-free coherent layer during Ruddlesden–Popper faults generation in LaNiO3 thin films

Bak Jumi,정성윤 한국세라믹학회 2021 한국세라믹학회지 Vol.58 No.2

Two-dimensional lattice defects, including surface and grain boundaries, in various perovskite oxides have garnered considerable attention, as the overall physical properties of the oxides can signifi cantly vary depending on the atomic and electronic structure of the defects. In particular, because Ruddlesden–Popper (RP) planar faults have a unique lattice structure with [ A O] monolayers being inserted in an AB O 3 perovskite framework, they have attracted considerable attention, resulting in various relevant studies being conducted. This study focuses on the eff ect of lattice strain on formation of RP faults and on critical thickness in (001) epitaxial LaNiO 3 thin-fi lm fabrication through a sol–gel process. Atomic-scale direct observations identifi es that a fault-free coherent buff er layer forms during the RP fault generation and its thickness varies depending on the strain exerted from the substrate. When DyScO 3 , the lattice mismatch of which is the largest, is used as a substrate, the critical thickness of the fault-free buff er layer remarkably reduces to a few unit cells. This work highlights the signifi cance of direct observation to understand the defect formation in perovskite oxides.

Magneto-capacitance Effects in Epitaxial TbMn2O5 Thin Films

송종현,강선희,김일원,정윤희,구태영 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.61 No.9

Thin films of TbMn<SUB>2</SUB>O<SUB>5</SUB><SUB> </SUB>(TMO) were grown on the Nb-doped TiO<SUB>2 </SUB>(110) substrates by pulsed laser deposition to investigate the effects of substrate-induced strains on the multiferroic properties observed in the bulk phase. Epitaxial qualities of the films were confirmed by x-ray azimuthal angle scans of TMO (201) and TiO<SUB>2</SUB> (111) reflections. TMO films were magnetically ordered below <I>T</I><SUB>N</SUB> ≈ 43 K, consistent with the value observed in the bulk. Maximum negative magneto-capacitance effect of about 10% at 8 T was detected near 16 K, where dielectric constant changed rapidly with a steplike anomaly. Magnetization-induced ferroelectric phases below T<SUB>N</SUB> appear to become destabilized in the epitaxial thin films due to the weakened magnetic exchange interactions by the substrate-induced tensile strains.

Epitaxial perovskite oxide thin films on Ba(Ti,Zr)O3 substrates for strain-induced electric/magnetic property changes near room temperature

K.D. Sung,Y. A. Park,허남정,정종훈,D. H. Kim,이보화 한국물리학회 2014 Current Applied Physics Vol.14 No.3

We have reported the epitaxial growth and the electric/magnetic properties of SrRuO3 and (La0.67Sr0.33) MnO3 thin films on Ba(Ti0.925Zr0.075)O3 substrates. The dielectric constant and thermal expansion of Ba(Ti0.925Zr0.075)O3 exhibited hysteretic jumps at the structural transition temperatures. Near the rhombohedral to orthorhombic structural transition temperature of Ba(Ti0.925Zr0.075)O3, which occurs at w33 C, we have observed a drastic jump of resistivity and magnetization of the thin films. These results suggest that epitaxial perovskite oxide thin films on Ba(Ti0.925Zr0.075)O3 substrates should be quite useful for the strain-induced changes of physical properties near room temperature.