Sung-Gaun Kim

Task-based and stable telenanomanipulation in a nanoscale virtual environment

In a haptic interface system with a nanoscale virtual environment (NVE) using an atomic force microscope, not only is stability important, but task-based performance (or fidelity) is crucial. In this paper, we introduce a nanoscale virtual coupling (NSVC) concept and explicitly derive the relationship between performance, stability, and scaling factors of velocity (or position) and force. An available scaling factor region is represented based on Llewellyns absolute stability criteria and the physical limitation of the haptic device. For the stable haptic interface, the sampled time passivity controller is implemented in the NVE. Experiments have been performed for telenanomanipulation tasks, such as positioning, indenting, and nanolithography with guaranteed stability in the NVE. Note to Practitioners-This paper suggests methods and control schemes for the task-based and stable telenanomanipulation in the nanoscale virtual environment (NVE). The proposed task-based and stable telenanomanipulation in the NVE can be used for an augmented human machine interface for the manipulation of nanoscale objects with the atomic force microscope (AFM). In addition, it is beneficial for learning or performing nanoscale tasks, such as nanolithography, nanoindenting, nanofabrication, and cell manipulation. Also, the interaction with the NVE using haptic device provides a useful tool for researchers in a variety of disciplines, such as biology, chemistry, and physics. Moreover, it may even be applied to educational purposes. In future research, the developed stable haptic interface would be integrated with the AFM system as a slave manipulator for telenanomanipulation experiments, such as pushing a nanoparticle with precise positioning and nanoassembly.

Adaptive Fabrication of a Flexible Electrode by Optically Self-Selected Interfacial Adhesion and Its Application to Highly Transparent and Conductive Film

A novel adaptive electrode fabrication method using optically self-selected interfacial adhesion between a laser-processed metal layer and polymer film is introduced to fabricate cost-effectively a high-resolution arbitrary electrode with high conductivity. The quality is close to that from vacuum deposition on a highly heat sensitive polymer film, with active response to various design requirements. A highly conductive metal film (resistivity: 3.6 μΩ cm) below a 5 μm line width with a uniform stepwise profile and mirror surface quality (R(rms) : 5-6 nm) is fabricated on a cheap polymer film with a heat resistance limit of below 100 °C. Severe durability tests are successfully completed without using any adhesion promoters. Finally, a highly transparent and conductive electrode with a transparency above 95% and sheet resistance of less than 10 Ω sq⁻¹ is fabricated on a polymer film and on glass by using this method. These results can help realize a potential high-throughput, low-cost, solution-processable replacement for transparent conductive oxides.

Study of the Spreading of Perfluoropolyether Lubricants on a Diamond-Like Carbon Film

Nonpolar perfluoropolyether (PFPE) Z and PFPE Zdol with polar end groups are widely used as hard disk lubricants for protecting carbon overcoats by reducing friction between the hard disk and head during movement of the head while reading and writing data on the hard disk. We investigate the spreading phenomenon of PFPE Z and PFPE Zdol on a thin diamond-like carbon (DLC) film adopting molecular dynamics (MD) simulations based on a coarse-grained bead-spring model to describe the thickness profiles and molecular movement, which evolve with time and temperature. In the present article, the hard disk surface was considered as a DLC and the position of its carbon atoms was obtained by heating and quenching the face-centered cubic (FCC) or body-centered cubic (BCC) diamond structures by MD simulation using the Tersoff potential. To simulate PFPE Z and PFPE Zdol on a thin DLC film using a coarse-grained bead-spring model based on finitely extensible nonlinear elastic potential and nonbonded potential, the original DLC thin film was compressed to half of its original configuration in all three spatial dimensions. How PFPE Z and PFPE Zdol on the DLC surface spread with time are briefly discussed. How the spreading profile of PFPE Z and PFPE Zdol on the DLC film spreads laterally and on the DLC film as a circular shape beyond its original position is also discussed. The effect of temperature on the film thickness and spreading area of PFPE Z and PFPE Zdol on the DLC film is also discussed. We show that the time dependence for the spreading of PFPE Z and PFPE Zdol droplets deviated from the expected proportionality to the square root of time in their spreading profiles with time. The model-calculated spreading rate of PFPE Z and PFPE Zdol on a thin DLC film increased inversely with absolute temperature as expected.

On the elastic, elastic-plastic properties of Au nanowires in the range of diameter 1-200 nm

In the present study, we obtain Youngs modulus and yield strength of 〈100〉 Au nanowire in the range of diameters 1-30 nm by tension and bending tests using molecular dynamics simulations. Double clamped Au nanowire is bended applying a point load at its middle span using cylindrical indenter by the atomistic approach. The superiority of the present bending technique is highlighted by analyzing the distribution of Von Misses stress of the present bending Au nanowire by 3D finite element modeling. First, Youngs modulus and yield strength of Au nanowires are determined using classical theory of continuum mechanics. Then the obtained Youngs modulus and yield strength of Au nanowires are corrected using 3D finite element modeling based on inverse technique [Deb Nath et al. Appl. Phys. A 103(2), 493 (2011) and Tohmyoh et al. Appl. Phys. A 103(2), 285 (2011)]. Effects of anisotropy on the tension and bending stiffness, tension and bending strength of Au nanowires are also discussed with graphs. Effects of tem...

Study of the Nanomechanics of CNTs under Tension by Molecular Dynamics Simulation Using Different Potentials

At four different strain rates, the tensile stress strain relationship of single-walled 12-12 CNT with aspect ratio 9.1 obtained by Rebo potential (Brenner, 1990), Airebo potential (Stuart et al., 2000), and Tersoff potential (Tersoff, 1988) is compared with that of Belytschko et al. (2002) to validate the present model. Five different empirical potentials such as Rebo potential (Brenner, 1990), Rebo potential (Brenner et al., 2002), Inclusion LJ with Rebo potential (Brenner, 1990), Airebo potential (Stuart et al., 2000), and Tersoff potential (Tersoff, 1988) are used to simulate CNT subjected to axial tension differing its geometry at high strain rate. In Rebo potential (Mashreghi and Moshksar, 2010) only bond-order term is used and in Rebo potential (Brenner et al., 2002) torsional term is included with the bond-order term. At high strain rate the obtained stress strain relationships of CNTs subjected to axial tension differing its geometries using five different potentials are compared with the published results and from the comparison of the results, the drawback of the published results and limitations of different potentials are evaluated and the appropriate potential is selected which is the best among all other potentials to study the elastic, elastic-plastic properties of different types of CNTs. The present study will help a new direction to get reliable elastic, elastic-plastic properties of CNTs at different strain rates. Effects of long range Van der Waals interaction and torsion affect the elastic, elastic-plastic properties of CNTs and why these two effects are really needed to consider in bond-order Rebo potential (Brenner, 1990) to get reliable elastic, elastic-plastic properties of CNTs is also discussed. Effects of length-to-diameter ratio, layering of CNTs, and different empirical potentials on the elastic, elastic-plastic properties of CNTs are discussed in graphical and tabular forms with published results as a comparative manner to understand the nanomechanics of CNTs under tension using molecular dynamics simulation.

Parallel laser fabrication of film-embedded microstructures using reusable functionalized template

This study proposes a new parallel mass-production method for obtaining microstructures embedded in flexible films, utilizing a laser-processed reusable functionalized template and a laser-induced adhesive transfer. This physical shape-free template can be cost-effectively fabricated by means of the laser-induced plasmonic defunctionalization of a self-assembled monolayer. The resulting metal nanoparticle microstructure, deposited self-selectively on the template, is transferred to a flexible film by a photo-induced instantaneous interfacial adhesion film in parallel; this process being optimized using molecular dynamics simulations. This method is demonstrated to be capable of the high-efficiency and eco-friendly production of high resolution and durable microstructures in flexible films, using a reusable template to eliminate material waste. Moreover, key design parameters such as the resolution, thickness, type, and shape of microstructures can be actively changed.

A Numerical Solution of a One End Fixed Glass/Epoxy Plate Having a Circular Cutout Subjected to a Uniform Shear Using Displacement Potential Approach.

The finite-difference technique based on the displacement potential approach of orthotropic composite materials is extended to solve elastic plane stress problems of orthotropic composite materials with geometric perturbations, such as holes, arbitrary defects, notches, etc. In this analysis, one fixed elastic glass/epoxy plate having an internal hole is considered and a uniform shear load is applied to the opposite end of the supporting edge. Critical sections of the plate are identified with the detailed discussions of the elastic field of the plate. Effects of sizes of the holes of the plate on the elastic field are also discussed with the help of graphical solutions. The reliability of the extended finite-difference technique based on the displacement potential approach of orthotropic composite materials is shown by the comparison of solutions between the FDM and FEM.

Effect of Tire Material on the Prediction of Optimum Tire-Tread Sections

The effect of tire material on the prediction of optimum shapes of tire treads is analyzed using the displacement potential based finite-difference technique. From the distribution of no-slip shearing stress along the contact surface of tire treads a relationship is established between the tire-tread sections and the frictional resistance required to keep the contact surface free from lateral slippage. Three different tire materials, such as natural rubber, original truck-tire rubber, and commercially available retreading tire-rubber, are considered for the present study. From the comparison of the calculated coefficient of friction with that available between the tire and road surface, optimum values of tire-tread sections are determined for three different tire materials, which ensure no lateral slippage of the contact surface on the road.

Atomistic modeling of scratching process based on Atomic Force Microscope: Effects of temperature

A three-dimensional molecular dynamics model has been used to investigate the effects of temperature during Atomic Force Microscopy (AFM) based scratching process. Effects of temperature have been taken into consideration as tribological properties are affected significantly by temperature. Deformation behavior, force components, tribological behavior and dislocations generation have been taken into consideration. It has been found that, low temperature like 200K is better choice considering these aspects of nanometric scratching process.

The Flow Rate Characteristics of External Gear Pump for EHPS

EHPS(Electro-Hydraulic Power Steering) system generates the steering operation force from the electric motor connected directly to the oil pump. When developing the steering system, the final specification of steering system is determined through the field test and the tuning process of the several times. In this paper, the flow rate measurement of an external gear pump was performed. Then by using the experimental results, an approximate model expressed by flow rate characteristics was proposed to calculate the discharge flow rate. The proposed approximate model was verified by comparison with the experimental data and AMESim results. As the experimental data and AMESim results agree well, the approximate model data can be used as an alternative to the highly expensive experimental procedure.