• Geomechanics and Engineering
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• v.12 no.5
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• pp.863-870
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• 2017

With the increasing interest in using bacterial biofilms in geo-engineering practices, such as soil improvement, sealing leakage in earth structures, and hydraulic barrier installation, understanding of the contribution of bacterial biofilm formation to mechanical and hydraulic behavior of soils is important. While mechanical properties of soft gel-like biofilms need to be identified for appropriate modeling and prediction of behaviors of biofilm-associated soils, elastic properties of biofilms remain poorly understood. Therefore, this study investigated the microscale Young's modulus of biofilms produced by Shewanella oneidensis MR-1 in a liquid phase. The indentation test was performed on a biofilm sample using the atomic force microscopy (AFM) with a spherical indentor, and the force-indentation responses were obtained during approach and retraction traces. Young's modulus of biofilms was estimated to be ~33-38 kPa from these force-indentation curves and Hertzian contact theory. It appears that the AFM indentation result captures the microscale local characteristics of biofilms and its stiffness is relatively large compared to the other methods, including rheometer and hydrodynamic shear tests, which reflect the average macro-scale behaviors. While modeling of mechanical behaviors of biofilm-associated soils requires the properties of each component, the obtained results provide information on the mechanical properties of biofilms that can be considered as cementing, gluing, or filling materials in soils.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2005.05a
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• pp.395-400
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• 2005

Nano-scale fabrication of silicon substrate based on the use of atomic force microscopy (AFM) was demonstrated. A specially designed cantilever with diamond tip, allowing the formation of damaged layer on silicon substrate by a simple scratching process, has been applied instead of conventional silicon cantilever for scanning. A thin damaged layer forms in the substrate at the diamond tip-sample junction along scanning path of the tip. The damaged layer withstands against wet chemical etching in aqueous KOH solution. Diamond tip acts as a patterning tool like mask film for lithography process. Hence these sequential processes, called tribo-nanolithography, TNL, can fabricate 2D or 3D micro structures in nanometer range. This study demonstrates the novel fabrication processes of the micro cantilever and diamond tip as a tool for TNL using micro-patterning, wet chemical etching and CVD. The developed TNL tools show outstanding machinability against single crystal silicon wafer. Hence, they are expected to have a possibility for industrial applications as a micro-to-nano machining tool.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.764-767
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• 2001

Because using LB method, result that produce Arachidic acid and Stearic acid LB film and measure the accumulation characteristic and electrical characteristic is as following. Organic monolayers of surface of the water compression each 9 layer's LB film to slide glass and manufactured MIM device compressing molecular film only. Could confirm that accumulation was good seeing as absorption coefficient and SEM picture, AFM picture that prevent manufactured LB films. Formation of domain of coexistence form that prevent LB film is indefinite and distinction of border side was not clear, and could know that roughness appears greatly. Obtained current by applied voltage could know that is proportional almost, though Arachidic acid appeared as bulk of current that happen in equaler certification voltage than Stearic acid is less, this alkyl chain longer Arachidic acid that serving relations special quality is superior know can .

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.5
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• pp.115-121
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• 2007

Phase contrast imaging in atomic force microscopy showed a promise as an effective tool for better understanding of micromechanical properties of surfaces at nano scale. A qualitative estimation model for phase contrast images obtained with a tapping mode AFM was developed. This investigation demonstrated the high efficiency of combined analysis of topography and phase contrast images for characterizing nanosurfaces. Phase contrast images allowed estimation of relative stiffness(elastic modulus) of the sample surface. The phase contrast images revealed a significant inhomogeneity of the nano scale worn surfaces. Phase contrast images are also capable of revealing the formation of tribofilms.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.12
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• pp.76-82
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• 1997

Chemical mechanical polishing (CMP) has become widely accepted for the planarization of multi-interconnect structures in semiconductor manufacturing. However, perfect planarization is not so easily ahieved because it depends on the pattern sensitivity, the large number of controllable process parameters, and the absence of a reliable process model, etc. In this paper, we realized the planarization of deposited oxide layers followed by metal (W) polishing as a replacement for tungsten etch-back process for via formation. Atomic force microscope (AFM) is used for the evaluation of pattern topography during CMP. As a result, AFM evaluation is very attractive compared to conventional methods for the measurment of planarity. mOreover, it will contribute to analyze planarization characteristics and establish CMP model.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.4
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• pp.595-599
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• 1996

The behaviour of the internal bubbles present in $CaF_{2}$ crystals was characterized crystallographically using a variety of the mircroscopical technique. The bubble defects were found to be aligned on the characteristic planes and directions depending on the crystals structure of the $CaF_{2}$. The AFM analysis revealed that these behaviors are related to the S-surface formation by the negative grain growth mechanism.

• Journal of the Korean Vacuum Society
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• v.15 no.2
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• pp.168-172
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• 2006

GaN nucleation layers were grown by hydride vapor phase epitaxy (HVPE) and the effect of growth temperature on the structural properties of GaN nucleation layers for nanorods was investigated by synchrotron x-ray scattering and Atomic Force Microscopy (AFM). For the samples grown at different temperatures, two-component rocking profiles of (002) GaN Bragg peaks for the GaN nucleation layers were observed with one very sharp and the other broad. It was shown that the two-component rocking profile could be qualitatively explained by surface morphology, which was in good agreement with AFM result, from which we could conclude that relatively low temperature is favorable for GaN nanorods formation.

• Bulletin of the Korean Chemical Society
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• v.20 no.8
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• pp.869-874
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• 1999

In this paper, electrochemical techniques are used to investigate hydrothermal-electrochemically formation of barium titanate (BT) ceramic films. For comparison, the electrochemical behaviors of anodic titanium oxide films formed in alkaline solution were also investigated both at room temperature and in hydrothermal condition at 150.0 ℃. Film structure and morphology were identified by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Titanium oxide films produced at different potentials exhibit different film morphology. The breakdown of titanium oxide films anodic growth on Ti electrode plays an important roles in the formation of BT films. BT films can grow on anodic oxide/metal substrate interface by short-circuit path, and the dissolution-precipitation processes on the ceramic film/solution interface control the film structure and morphology. Based upon the current experimental results and our previous work, extensively schematic proce-dures are proposed to model the mechanism of ceramic film formation by hydrothermal-electrochemical method.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.6
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• pp.1313-1318
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• 2006

The mechanism fur the surface film formation was studied by in situ Atomic Force Microscopy (AFM) observation of a highly oriented pyrolytic graphite (HOPG) basal plane surface during cyclic voltammetry at a slow scan-rate of 0.5 mV $s^{-1}$ in 1 moi $dm^{-3}$ (M) $LiPF_6$ dissolved in a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC). Decomposition of the electrolyte solution began at a potential around 2.15 V vs. $Li^+$/Li on step edges. In the potential range 0.95-0.8 V vs. $Li^+$/Li, flat areas (hill-like structures) and large swelling appeared on the surface. It is considered that these two features were formed by the intercalation of solvated lithium ions and their decomposition beneath the surface, respectively. At potentials more negative than 0.80 V vs. $Li^+$/Li, particle-like precipitates appeared on the basal plane surface. After the first cycle, the thickness of the precipitate layer was 30 nm. The precipitates were considered to be decomposition of the lithium salt ($LiPF_6$) and solvent molecules (EC and DEC), and to have an important role in suppressing further solvent decomposition on the basal plane.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.47 no.2
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• pp.163-170
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• 2021

This study was conducted to create a technology to remove acne bacteria with human-friendly materials. First, the Cutibacterium acnes (C. acnes) were adsorbed to the mica disc to grow, and then the biofilm was checked through an atomic microscope to see if the biofilm had grown. Based on the topographic image, the shape changed round, the size was 17% longer on average, and the phase value of the resonance frequency separating materials was observed as a single value, the biofilm grown by covering the extracellular polymeric substrate (EPS). As a result of processing 50 mM of amino acids in the matured biofilm, the concentration of C. acnes decreased when valine, serine, arginine and leucine were treated. Scanning with nanoindentation and AFM contact modes confirmed that the hardness of biofilms treated with Valine (Val) increased. This indicates that an AFM tip measured cell which may have more solidity than that of EPS. The experiment of fluorescent tagged to EPS displays an existence of EPS at the condition of 10 mM Val, but an inhibition of growth of EPS at the 50 mM Val. Number of C. acnes was also reduced above 10 mM of Val. Weak adhesion of biofilm generated from an inhibition of EPS formation seems to induce decrease of C. acnes. Accordingly, we elucidated that Val has an efficiency which eliminates C. acnes by approach of an inhibition of EPS.