• Journal of the Semiconductor & Display Technology
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• v.10 no.3
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• pp.49-52
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• 2011

This paper shows the results of classical molecular dynamics modeling for the interaction between spherical nano abrasive and substrate in chemical mechanical polishing processes. Atomistic modeling was achieved from 3-dimensional molecular dynamics simulations using the Morse potential functions for chemical mechanical polishing. The abrasive dynamics was modeled by three cases, such as slipping, rolling, and rotating. Simulation results showed that the different dynamics of the abrasive results the different features of surfaces. The simulation concerning polishing pad, abrasive particles and the substrate has same results.

• Journal of Radiopharmaceuticals and Molecular Probes
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• v.9 no.1
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• pp.43-48
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• 2023

For over 50 years, boron neutron capture therapy (BNCT) has been steadily developed for treating various cancers. This is a non-invasive, selective, and targeted radiotherapy wherein boron-rich molecules accumulate at the tumor site. Liposomal vesicles have become a popular and effective drug delivery system for BNCT, with strategies including surface decoration, bilayer integration, and hydrophilic core encapsulation. This review highlights the state-of-the-art uses of liposomes in BNCT and elucidates a new perspective where BNCT can be used with radiotracer guidance in all-in-one delivery systems.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.4
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• pp.135-142
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• 1995

Recently, the analysis of microcutting with submicrometer depth of cut is tried to get a more high quality surface product, but to get a valuable result another method instead of conventional finite element method must be considered because finite element method is impossible for a very small focused region and mesh size. As the alternative method, Molecular Dynamics or Statics is suggested and accepted in the field of microcutting, indentation and crack propagation. In this paper using Molecular Dynamics simulation, the phenomena of microcutting with subnanometer chip thickness is studied and the cutting mechanism for tool edge configuration is evaluated. As the result of simulation the atomistic chip formation is achieved.

• Bulletin of the Korean Chemical Society
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• v.33 no.3
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• pp.775-778
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• 2012

The potential energy surfaces of ammonia molecule adsorptions on the symmetrically chlorinated Si(100)-$2{\times}1$ surface were explored with SIMOMM:MP2/6-31G(d). It was found that the initial nucleophilic attack by ammonia nitrogen to the surface Si forms a $S_N2$ type transition state, which eventually leads to an HCl molecular desorption. The second ammonia molecule adsorption requires much less reaction barrier, which can be rationalized by the surface cooperative effect. In general, it was shown that the surface Si-Cl bonds can be easily subjected to the substitution reactions by ammonia molecules yielding symmetric surface Si-$NH_2$ bonds, which can be a good initial template for subsequent surface chemical modifications. The ammonia adsorptions are in general more facile than the corresponding water adsorption, since ammonia is better nucleophile.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.3
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• pp.250-257
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• 2008

We calculate the variation of the surface stresses according to uniaxial and biaxial strains in face-centered cubic (FCC) metals. In our study, three mainly observed free surfaces of seven representative FCC metals are considered. Employed method is molecular mechanics, in which the interaction of atoms is described by empirical interatomic potentials. As uniaxial strain increases to tensile direction, the surface stresses on {100} and {110} free surfaces decrease monotonously, while those on {111} surface increase. These tendencies are the same regardless of the species of metals and interatomic potentials employed. However, when the system is under biaxial strain, surface stresses change different according to the surface directions, the species of metals, and even interatomic potentials. On {100} and {111} surfaces, heavy metals (Pt, Au) show the opposite variation to light metals (Ni, Cu). In the cases of Pd and Ag, the surface stresses reveal the opposite tendency, depending on interatomic potentials used.

• Journal of the Korean institute of surface engineering
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• v.39 no.4
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• pp.166-172
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• 2006

Metallized Polyimide films are extensively used as base materials in microelectronics, optical and automotive applications. However it is difficult to deposit metals on those because of their structural stabilities. In this work, polyimide films are modified by a wet process with alkalinemetalhydroxide and additives to introduce functional groups. The surface molecular structures of polyimide are investigated using X-ray photoelectron spectroscopy(XPS), fourier transform infrared reflection spectroscopy(FTIR-ATR), atomic force micro-scopic(AFM). XPS spectra and FTIR spectra show that the surface structure of polyimide is converted into potassium polyamate. AFM image and AFM cross-sectional analyses reveal the increased roughness on the modified surface of polyimide films. As a result, it is shown that the adhesion strength between polyimide surface and electroless nickel layer is increased by the nano-anchoring effect.

• Journal of Mechanical Science and Technology
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• v.20 no.9
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• pp.1483-1491
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• 2006

The pumping performance of molecular drag pumps (MDP) has been investigated experimentally. The exporimented MDPs are a disk-type drag pump (DTDP), helical-type drag pump(HTDP) and compound drag pump (CDP), respectively In the case of the DTDP, spiral channels of a rotor are cut on both upper surface and lower surface of a rotating disk, and the corresponding stator is a planar disk. In the case of the HTDP, the rotor has six rectangular grooves. The CDP consists with the DTDP, at lower part, and with the HTDP, at upper part. The experiments are performed in the outlet pressure range of $0.2{\sim}533Pa$. The inlet pressure and compression ratio are measured under the various conditions of outlet pressure and throughputs, and nitrogen is used for the test gas. At the outlet pressure of 0.2Pa, the ultimate pressure has been reached to $1.0{\times}10^{-2}Pa$ for the HTDP, $1.3{\times}10^{-4}Pa$ for the DTDP, and $3.6{\times}10^{-5}Pa$ for the CDP. The maximum compression ratio of the CDP is much higher than those of the DTDP or HTDP. Consequently, the ultimate pressure of the CDP is the lowest one.

• Bulletin of the Korean Chemical Society
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• v.35 no.5
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• pp.1333-1336
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• 2014

Expanded polytetrafluoroethylene (ePTFE) grafts have been used as vascular access for many patients suffering from end stage renal disease. However, the vascular graft can cause significant clinical problems such as stenosis or thrombosis. For this reason, many studies have been performed to make drug eluting graft, but initial burst is major problem in almost drug eluting systems. Therefore we used biodegradable polymer to reduce initial burst and make sustained drug delivery. The ePTFE grafts were dipped into a paclitaxel-dissolved solution and then PLGA-dissolved solution was passed through the lumen of ePTFE. We analyzed whether the dose of paclitaxel is enough and the loading amount of PLGA on ePTFE graft increases according to the coating solution's concentration. Scanning electron microscope (SEM) images of various concentration of PLGA showed that the porous surface of graft was more packed with PLGA by tetrahydrofuran solution dissolved PLGA. In addition, in vitro release profiles of Ptx-PLGA graft demonstrated that early burst was gradually decreased as increasing the concentration of PLGA. These results suggest that PLGA coating of Ptx loaded graft can retard drug release, it is useful tool to control drug release of medical devices.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.6
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• pp.590-596
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• 1999

The effects of additives on the Zn electrodeposition in chloride-based electrolyte were investigated using circulation cell with three electrodes system. The cathodic polarization increased with the addition of polyethylenglycol (hereafter PEG) in electrolyte. This was attributed to the adsorption of the additives on the electrode and the inhibition of migration of metal ion. The PEG, however, did not have any noticeable effect on the properties of plating solutions at the concentration used. The effect of PEG on the electrocrystallization was related to its molecular weight. With the increase of molecular weight, the cathodic polarization increased, while the surface roughness was improved with the decrease of brightness. Especially, the PEG mixed with different molecular weights was the most effective. The orientation and the type of the deposited grains were changed and refined by PEG, which resulted in the modification of deposited surface roughness and brightness.

• BMB Reports
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• v.30 no.5
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• pp.308-314
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• 1997

We investigated biotinylation of nitrocellulose membrane for immuno-filtration capture assay. In order to enhance the efficiency of biotinylation, nitrocellulose membranes were pretreated with several chemicals for the purpose of suitable protein absorption through surface modification. As a signal generating enzyme, urease was used and the concentration of avidin was optimized for the efficient binding kinetics between urease-biotin in liquid phase and biotinylated membrane in solid phase. For effective biotinylation, bovine serum albumin-biotin complexes could be immobilized at a concentration of $370\;{\mu}g$/stick ($4.4\;cm^2$). Among tested chemicals, polylysine (0.25%) showed a significant effect in biotinylation. Polylysine is thought to enhance surface area by extending unbound residues into solution. Time of treatment over 30 min and higher molecular weight of polylysines (58,100 dalton) showed positive effect on the enhancement of biotinylation. The result from this study may be useful for developing a new biosensor and other biofunctional membranes for examining molecular recognition.