AFM을 이용한 얼굴과 하박내측 각질세포 표면 특성 비교연구

장민열 ( Minyoul Chang ) 대한화장품학회 2019 대한화장품학회지 Vol.45 No.4

얼굴과 하박내측의 피부는 경피수분손실량(TEWL), 피부 수분량, 탄력 등에서 많은 차이를 보이고 있다. 특히, 이전 연구 결과에서 얼굴피부와 하박내측 피부는 수화(hydrating) 과정에 따른 탄력특성의 차이를 보여 주었다. 이에 본 연구에서는 신체부위에 따른 피부특성 차이는 각 신체부위를 구성하고 있는 각질세포 특성과 연관성이 있을 것이라는 가정하에 atomic force microscopy (AFM)을 이용하여 각질세포 표면 특성을 비교 연구하였다. 각질세포 표면의 거칠기(roughness)와 villus-like projections (VPs)을 이용하여 비교 평가하였다. 더 나아가 얼굴피부, 하박내측, 입술 피부의 각질세포 표면을 정성적으로 비교해 보았다. 각질세포는 8명의 피험자의 얼굴과 하박내측 피부에서 tape-stripping을 이용하여 채취하여, AFM을 이용하여 40 μm x 40 μm 크기로 각질세포의 아랫면 표면 특성(bottom surface of corneocyte)을 측정하였다. 그 결과, 얼굴 각질세포 아랫면 표면 거칠기는 388.34 ± 86.189 nm이었고, 하박내측 각질세포 아랫면 표면 거칠기는 662.27 ± 224.257 nm로 하박내측 각질세포가 얼굴 각질세포보다 더 거친 표면 특성임을 확인하였다( p < 0.001). 관찰된 VPs의 양을 비교해보면, 입술 각질세포가 가장 많았고, 그 다음이 얼굴 각질세포이며, 하박내측 각질세포는 낮은 수준이었다. 이러한 결과를 통해 볼때, 각질세포 표면 특성이 얼굴과 하박내측 피부 사이에 보이는 특성 차이에 어느 정도 관여하고 있음을 확인할 수 있었으며, VPs는 부위별 피부 특성 연구에 유용한 parameter가 될 수 있는 가능성도 확인할 수 있었다. 그리고, AFM은 각질세포 표면의 미세한 구조적 차이를 비교 연구하는데 매우 유용한 기기임을 알 수 있었다. 향후 조금 더 많은 연구가 진행된다면 각질세포에 대한 새로운 화장품 효능 평가법이 개발될 것으로 사료된다. There are many differences in trans-epidermal water loss (TEWL), skin water contents, and skin elasticity, etc between face and forearm skin. In particular, our previous studies showed that elasticity of face skin was significantly differed from forearm depending on full hydration. So, we have studied the surface properties of corneocyte using atomic force microscopy (AFM), assuming that the differences between face and forearm skin would be associated with the surface properties of corneocyte. The surface roughness of corneocyte and villus-like projections (VPs) were measured. Furthermore, qualitative comparison among the surface of face, forearm, and lip corneocyte was performed. Corneocytes were collected by tape-stripping on both face and forearm of 8 volunteers, and the bottom surface of corneocytes were measured at 40 μm × 40 μm using AFM. Results showed that the lower surface roughness of face corneocytes was 388.34 ± 86.189 nm, and that of forearm corneocytes was 662.27 ± 224.257 nm, which confirmed that the lower surface of forearm corneocytes was more rough than that of face corneocytes (p < 0.001). Compared with the amount of VPs, lip corneocytes were the highest followed by face corneocytes, and forearm corneocytes were the lowest. From these results, it is conclued that the surface properties of corneocytes are somewhat involved in the property differences between the face and the forearm skin and VPs can be a useful parameter for the study of corneocyte by site. In addition, AFM is a very useful device for the comparative study of nano-structural differences on the surface of corneocytes. More studies can lead to develop a new evaluation method of corneocytes.

Si (001) 표면 결함 원자힘 현미경 전산모사

조준영,김대희,김유리,김기영,김영철 한국반도체디스플레이기술학회 2018 반도체디스플레이기술학회지 Vol.17 No.4

Atomic force microscopy (AFM) simulation for Si (001) surface defects was conducted by using density functional theory (DFT). Three major defects on the silicon (001) surface are difficult to analyze due to external noises that are always present in the images obtained by AFM. Noise-free surface defects obtained by simulation can help identify the real surface defects on AFM images. The surface defects were first optimized by using a DFT code. The AFM tip was designed by using five carbon atoms and positioned on the surface to calculate the system’s energy. Forces between tip and surface were calculated from the energy data and converted into an AFM image. The simulated AFM images are noise-free and, therefore, can help evaluate the real surface defects present on the measured AFM images.

Interfacial Strength and Surface Damage Characteristics of Atomically Thin h-BN, MoS₂, and Graphene

Tran Khac, Bien-Cuong,DelRio, Frank W.,Chung, Koo-Hyun American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.10

<P>Surface damage characteristics of single- and multilayer hexagonal boron nitride (h-BN), molybdenum disulfide (MoS<SUB>2</SUB>), and graphene films were systematically investigated via atomic force microscopy (AFM)-based progressive-force and constant-force scratch tests and Raman spectroscopy. The film-to-substrate interfacial strengths of these atomically thin films were assessed based on their critical forces (i.e., the normal force where the atomically thin film was delaminated from the underlying substrate), as determined from progressive-force scratch tests. The evolution of surface damage with respect to normal force was further investigated using constant-force tests. The results showed that single-layer h-BN, MoS<SUB>2</SUB>, and graphene strongly adhere to the SiO<SUB>2</SUB> substrate, which significantly improves its tribological performance. Moreover, defect formation induced by scratch testing was found to affect the topography and friction force differently prior to failure, which points to distinct surface damage characteristics. Interestingly, the residual strains at scratched areas suggest that the scratch test-induced in-plane compressive strains were dominant over tensile strains, thereby leading to buckling in front of the scratching tip and eventually failure at sufficient strains. These trends represent the general failure mechanisms of atomically thin materials because of a scratch test. As the number of layers increased, the tribological performances of atomically thin h-BN, MoS<SUB>2</SUB>, and graphene were found to significantly improve because of an increase in the interfacial strengths and a decrease in the surface damage and friction force. In all, the findings on the distinctive surface damage characteristics and general failure mechanisms are useful for the design of reliable, protective and solid-lubricant coating layers based on these materials for nanoscale devices.</P> [FIG OMISSION]</BR>

원자현미경을 이용한 탄화규소 (SiC)의 국소산화

조영득,방욱,김상철,김남균,구상모,Jo, Yeong-Deuk,Bahng, Wook,Kim, Sang-Cheol,Kim, Nam-Kyun,Koo, Sang-Mo 한국전기전자재료학회 2009 전기전자재료학회논문지 Vol.22 No.8

The local oxidation using an atomic force microscopy (AFM) is useful for Si-based fabrication of nanoscale structures and devices. SiC is a wide band-gap material that has advantages such as high-power, high-temperature and high-frequency in applications, and among several SiC polytypes, 4H-SiC is the most attractive polytype due to the high electron mobility. However, the AFM local oxidation of 4H-SiC for fabrication is still difficult, mainly due to the physical hardness and chemical inactivity of SiC. In this paper, we investigated the local oxidation of 4H-SiC surface using an AFM. We fabricated oxide patterns using a contact mode AFM with a Pt/Ir-coated Si tip (N-type, 0.01-0.025 ${\Omega}cm$) at room temperature, and the relative humidity ranged from 40 to 50 %. The height of the fabricated oxide pattern (1-3 nm) on SiC is similar to that of typically obtained on Si ($10^{15}^{\sim}10^{17}$ $cm^{-3}$). We perform the 2-D simulation to further analyze the electric field between the tip and the surface. We demonstrated that a specific electric field (4 ${\times}$ $10^7\;V/m$) and a doping concentration ($^{\sim}10^{17}$ $cm^{-3}$) is sufficient to switch on/off the growth of the local oxide on SiC.

원자현미경 (AFM)을 이용한 환경오염물질에 노출된 HeLa 세포의 표면변화 연구

이시원(Si-won Lee),이수일(Soo il Lee),최진희(Jinhee Choi) 환경독성보건학회 2008 환경독성보건학회지 Vol.23 No.1

The toxicity of environmental pollutants was measured between a image of the surface topography in HeLa cells using atomic force microscopy for the possibility of toxic effect measurement and environmental monitoring. A image of the surface topography by AFM were estimated as toxic endpoints. The surface topography by AFM was observed a change of the cell surface in the environmental pollutants, but the standard of the measurement requires for the dose-effect degree. The overall results indicate that the possibility of measurement using AFM were confirmed a dose-effect degree related toxic effects, but it requres correlation between more various biomarker and AFM's measurements if the possibility of the toxic effect measurement was established.

AFM을 이용한 나노 패턴 형성과 크기에 따른 광특성 시뮬레이션

황민영,문경숙,구상모,Hwang, Min-Young,Moon, Kyoung-Sook,Koo, Sang-Mo 한국전기전자재료학회 2010 전기전자재료학회논문지 Vol.23 No.6

We report a top-down approach based on atomic force microscopy (AFM) local anodic oxidation for the fabrication of the nano-pattern field effect transistors (FETs). AFM anodic oxidation is relatively a simple process in atmosphere at room temperature but it still can result in patterns with a high spatial resolution, and compatibility with conventional silicon CMOS process. In this work, we study nano-pattern FETs for various cross-bar distance value D, from ${\sim}0.5\;{\mu}m$ to $1\;{\mu}m$. We compare the optical characteristics of the patterned FETs and of the reference FETs based on both 2-dimensional simulation and experimental results for the wavelength from 100 nm to 900 nm. The simulated the drain current of the nano-patterned FETs shows significantly higher value incident the reference FETs from ${\sim}1.7\;{\times}\;10^{-6}A$ to ${\sim}2.3\;{\times}\;10^{-6}A$ in the infrared range. The fabricated surface texturing of photo-transistors may be applied for high-efficiency photovoltaic devices.

Effect of heating cycle on cobalt-antimonide-based thin films for high-temperature thermoelectric energy conversion applications

Ahmed, Aziz,Han, Seungwoo Elsevier 2019 JOURNAL OF ALLOYS AND COMPOUNDS Vol.790 No.-

<P><B>Abstract</B></P> <P>In this study, a comparative analysis of the structural and thermoelectric properties of all possible Co-Sb-based phases in thin-film form for high-temperature applications is presented and discussed. A series of thin-film samples were prepared via radiofrequency co-sputtering on an oxidized silicon substrate. For improved crystallinity, the thin-film samples were subjected to heat treatment in the form of a high-temperature heating cycle where the temperature was slowly ramped up to about 760 K. The films were characterized using X-ray diffraction for phase identification and crystalline quality. Energy-dispersive spectroscopy was performed to determine the stoichiometric composition and homogeneity, whereas the surface morphology and microstructure were examined using scanning electron microscopy and atomic force microscopy. To investigate film performance at high temperatures, the electrical resistivity and Seebeck coefficient were measured at regular temperature intervals, and results were correlated with identified phases, composition, and crystalline quality. The CoSb phase was observed to have metallic features, the CoSb<SUB>2</SUB> phase had doped semiconductor characteristics, whereas the CoSb<SUB>3</SUB>-phase thin films showed typical semiconductor behavior. The CoSb<SUB>2</SUB> and CoSb<SUB>3</SUB> samples shows a transition of the Seebeck coefficient from positive to negative at a temperature range of 500–550 K and 550–600 K respectively. The thermoelectric power factor was evaluated from the measured parameters and maximum values of 3.2, 7.8, and 3.8 mWm<SUP>−1</SUP>·K<SUP>−2</SUP> for the CoSb, CoSb<SUB>2</SUB>, and CoSb<SUB>3</SUB> thin films, respectively, are reported. We observed a wide range of structural and thermoelectric properties in the series of samples, demonstrating a route to tailoring and improving properties for maximal performance.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Thermopower depends upon both the carrier concentration and electron effective mass. </LI> <LI> The presence of impurity phases shapes the magnitude of the Seebeck coefficient. </LI> <LI> Seebeck coefficient retained the p to n type transition in the second heating cycle. </LI> <LI> A Seebeck coefficient as high as −227 μV/K was achievable for CoSb<SUB>3</SUB> thin films. </LI> <LI> CoSb<SUB>3</SUB> skutterudite thin films achieved a sound maximum power factor of 4 mW/m.K<SUP>2</SUP>. </LI> </UL> </P>

Local-dependency of morphological and optical properties between breast cancer cell lines

Lee, Seung Ho,Kim, Ok-Kyun,Lee, Sanghwa,Kim, Jun Ki Elsevier 2018 Spectrochimica acta. Part A, Molecular and biomole Vol.205 No.-

<P><B>Abstract</B></P> <P>Breast cancer is the most malignant type of cancer in women and is a global health problem, with mortality by metastasis being the main factor among others. Currently, detection and diagnosis of breast cancer is achieved through a variety of procedures, such as clinical examination, medical imaging, biopsy, and histopathological analysis. In contrast, spectroscopic analysis has a variety of advantages such as being noninvasive, not destroying biological materials, and not requiring additional histological analysis. In this study, various approaches using Raman spectroscopy, atomic force microscopy (AFM), and optical microscopy were used together to differentiate between and characterize normal breast cell lines (MCF-10A) and breast cancer cell lines (MDA-MB-231, MDA-MB-453). Raman spectra of normal breast cell and breast cancer cell lines confirmed visual differences in the concentrations of various compounds. These spectra were also analyzed using principle component analysis (PCA), and the PCA results showed reliable separation of the three cell lines and the cancer cell lines (MDA-MB-231, MDA-MB-453). With these results, optically synchronizing the AFM morphology, the Raman spectroscopy, and the visible RGB optical transmission intensity provided contrasts for not only conformational differences but also intracellular variation between the normal and cancer cell lines. We observed the inherent characteristic that there is no local difference in cancer cells regardless of morphology in a wide range of optical properties such as absorption, scattering and inelastic scattering.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The inherent optical properties of cancer cells separated from normal cells in terms of local variation were observed. </LI> <LI> Raman spectra and its PCA results of normal breast cell and breast cancer cell lines were confirmed to be visual differences. </LI> <LI> The RGB transmission imaging is also compared to the morphological difference obtained from AFM. </LI> <LI> In cancer cells, the conformational difference did not appear to be dependent on the intracellular location. </LI> </UL> </P> <P><B>Graphical Abstract</B></P> <P>[DISPLAY OMISSION]</P>

Nanoscale quantitative mechanical mapping of poly dimethylsiloxane in a time dependent fashion

Zhang, Shuting,Ji, Yu,Ma, Chunhua Techno-Press 2021 Advances in nano research Vol.10 No.3

Polydimethylsiloxane (PDMS) is one of the most widely adopted silicon-based organic polymeric elastomers. Elastomeric nanostructures are normally required to accomplish an explicit mechanical role and correspondingly their mechanical properties are crucial to affect device and material performance. Despite its wide application, the mechanical properties of PDMS are yet fully understood. In particular, the time dependent mechanical response of PDMS has not been fully elucidated. Here, utilizing state-of-the-art PeakForce Quantitative Nanomechanical Mapping (PFQNM) together with Force Volume (FV) and Fast Force Volume (FFV), the elastic moduli of PDMS samples were assessed in a time-dependent fashion. Specifically, the acquisition frequency was discretely changed four orders of magnitude from 0.1 Hz up to 2 kHz. Careful calibrations were done. Force data were fitted with a linearized DMT contact mechanics model considering surface adhesion force. Increased Young's modulus was discovered with increasing acquisition frequency. It was measured 878 ± 274 kPa at 0.1 Hz and increased to 4586 ± 758 kPa at 2 kHz. The robust local probing of mechanical measurement as well as unprecedented high-resolution topography imaging open new avenues for quantitative nanomechanical mapping of soft polymers, and can be extended to soft biological systems.

Selective Growth of Au Nanoparticles on PZT Substrates by Using a Photochemical Reaction

김정훈,양우철 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.60 No.10

We report the surface distribution of Au nanoparticles (NPs) grown on polarity-patterned ferroelectrics by using photochemical-reaction deposition. Polycrystalline lead zirconate titanate (PZT) was used as a ferroelectric substrate. The local polarization orientation on the surface was patterned by using atomic force microscopy (AFM). The Au NPs were grown by ultraviolet (UV) light exposure of the polarity-patterned PZT substrates while immersed in Au salt solutions. The wavelength dependence of the deposition of the NPs was investigated using UV band pass filters. The dimensions and the surface distribution of the NPs were measured by using AFM. For UV light without a filter, more NPs were formed on the +z polarity region than on the other regions. However, for UV light with wavelengths of 315 nm and 365 nm, we observed the selective deposition of NPs on +z polar domains. The NPs on the +z polar domains were denser and larger than those on the other non-polar regions. The average size of the NPs was ∼30 nm and the number density was ∼22/μm². In addition, the electron affinity of the PZT was found to be 3.0 eV from scanning Kelvin probe microscopy measurements of the PZT film surface with the deposition of Au NPs. This study suggests the possibility of controlling the sizes and the positions of Au NPs on a surface by optimizing the UV wavelength and polarity patterning of the ferroelectrics.