Jae-Jong Lee

Fabrication of a nano-scale pattern with various functional materials using electrohydrodynamic lithography and functionalization

Direct patterning with inorganic based materials has been studied using many lithographic techniques. Among lithographic methods, electro-hydrodynamic lithography (EHL) is a good candidate to obtain a fine inorganic pattern. Being a minimal contact patterning technique, our method is simple, versatile and inexpensive, and has the potential to become a powerful tool for realizing inorganic based nanostructures on a wafer scale. Inorganic precursor resists are exploited here as relatively high-speed resists compared to macromolecule resists in an effort to reduce the patterning time significantly. These resists are developed to have functionalities via a thermal annealing process which can be used in versatile applications. An amorphous inorganic precursor pattern fabricated by EHL is transitioned to a crystalline phase via an annealing process. Herein, functional material patterns such as TiO2, VO2, Fe3O4, and PZT are successfully fabricated and functionalized via EHL and the annealing process.

Ultrafast and low temperature laser annealing for crystalline TiO2 nanostructures patterned by electro-hydrodynamic lithography

Direct patterning of inorganic materials based on electro-hydrodynamic lithography (EHL) has attracted tremendous attentions as next generation soft-lithography technologies owing to its simple and cost-effective process. We show that the EHL technique based nanoscale inorganic pattern transfer coupled with ultrafast laser annealing is suitable for obtaining nanostructured TiO2 over a large area with great fidelity. The laser annealing technique enables us to overcome a technical issue of EHL associated with long processing time and high annealing temperature. We further demonstrated the enhanced switching performance by using the laser annealed TiO2 layer as an electron transport layer in the electro-chromic device.

Double-Pitch Dual Grating Method for Detecting the Axial Offset in Roll System

We propose a dual grating alignment technique for roll-to-roll positioning which allows achieving nanometer scale alignment by using micro-size marks. The high precision alignment system were designed and manufactured. It was confirmed that the optical system was properly adjusted and fully aligned with the dual gratings. The experiment and computer simulation results were presented. Alignment accuracy below 50 nm was achieved.

A Piezo-Driven Grating Scanner Based on Flexure Hinges for Measuring 3-Dimensional Microscopic Surface

This paper proposes a grating scanner which is driven by a stack-type piezoelectric element. The mechanism of the grating scanner is based on flexure hinges. Using some constraints, the compliant mechanism is designed and then verified by Finite Element Analysis. The designed compliant mechanism is manufactured by wire electro-discharge machining, and then integrated with a stack-type piezoelectric element for actuation and a capacitance displacement sensor for measuring ultra-precision displacement. Experiments demonstrates the characteristics and the performances of the grating scanner using the terms of working range, resonance frequency, bandwidth and resolution. The grating scanner is applicable to a Moire interferometry for measuring 3-dimensional microscopic surface.

A Piezo-driven Fine Manipulation System Based on Flexure Hinges for Manipulating Micro Parts

This paper presents a manipulation system consisting of a coarse/fine XY positioning system and an out-of-plane manipulator. The object of the system is to conduct tine positioning and manipulation of micro parts. The fine stage and the out-of-plane manipulator have compliant mechanisms with flexure hinges, which are driven by stack-type piezoelectric elements. In the fine stage, the compliant mechanism plays the roles of motion guide and displacement amplification. The out-of-plane manipulator contains three piezo-driven compliant mechanisms for large working range and fine resolution. For large displacement, the compliant mechanism is implemented by a two-step displacement amplification mechanism. The compliant mechanisms are manufactured by wire electro-discharge machining for flexure hinges. Experiments demonstrate that the developed system is applicable to a fine positioning and fine manipulation of micro parts.

Numerical studies for combustion processes and emissions in the DI diesel engines using EGR

The effects of exhaust gas recirculation on diesel engine combustion and soot/NOx emissions are numerically studied. The primary and secondary atomization is modelled using the wave instability breakup model. Autoignition of a diesel spray is modelled using the Shell ignition model. Soot formation is kinetically controlled and soot oxidation is represented by a model which account for surface chemistry. The NOx formation is based on the extended Zeldovich NOx model. Effects of injection timing and concentration of and CO on the pollutant formation and the combustion process are discussed in detail.