Biomedical subjects

Jooho Moon

Publications and source records attributed to Jooho Moon.

4 recordsLinked to original sources

PubMed2006

Control of colloidal particle deposit patterns within picoliter droplets ejected by ink-jet printing.

Particle deposit morphologies that resulted from evaporating ink-jetted microdroplets were controlled by varying the ink compositions and concentrations. The ink was a well-dispersed aqueous dispersion of monodisperse silica microspheres. Silica particles suspended in the microdroplet undergo self-assembly upon the evaporation of the solvent. A ringlike deposit of the self-assembled silica particles was produced from the water-based ink, while a uniform two-dimensional monolayer with a well-ordered hexagonal structure was obtained from the mixed-solvent-based inks. Variations in the deposit patterns can be explained in terms of competing effects between the convective and Marangoni flows, which vary with the types of the high-boiling-point solvent added to the ink. The macroscopic shape and microstructure of the silica colloidal deposits were observed by SEM, AFM, and a confocal microscope.

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PubMed2006

Direct-write fabrication of colloidal photonic crystal microarrays by ink-jet printing.

An array of the colloidal photonic crystals was directly fabricated using an ink-jet printing. The colloidal ink droplets containing the monodispersed polystyrene latex particles were selectively deposited on a hydrophobic surface. Solvent evaporation from each ink droplet leads to a formation of microdome-shaped colloidal assembles of close-packed structures. Microspectroscopic analysis has confirmed that the individual assembly serves as a photonic crystal and its optical properties can be correlated with the microstructural features. Unlike other techniques of patterned growth of colloidal photonic crystal, the substrate does not need to be patterned first and no template is needed in the direct writing by the ink-jet printing. Using our strategy, we have rapidly produced the colloidal photonic crystal microarrays composed of different-sized spheres addressably patterned on the same substrate.

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PubMed2005

Uniform Y2O3 coating on multi-component phosphor powders by modified polyol process.

We have developed a method to coat the phosphors comprising of multi-component systems to prevent them from aging effect. Y2O3 was selected as a protective material because of its superior ability to resist against mercury adsorption and oxidation and its good UV transparency at the wavelength used for phosphor activation. By dispersing the phosphor particles in the polyol medium that contains the yttrium precursor, heterogeneous nucleation and growth on the particle surface were induced. This allows us to obtain a thick and uniform coating of the phosphors with amorphous Y2O3 sols. The heat-treatment condition for Y3O3 sols was carefully controlled to keep the phosphors from surface oxidation and at the same time to assure the complete crystallization and burn-out of organic impurity by XRD and TG/DTA. The surface morphology of the coated phosphors was examined by SEM as a function of reaction time and temperature and precursor concentration.

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PubMed2002

Read/write mechanisms and data storage system using atomic force microscopy and MEMS technology.

Information storage system that has a potentially ultrahigh storage density based on the principles of atomic force microscopy (AFM) has been developed. Micro-electro-mechanical systems (MEMS) technology plays a major role in integration and miniaturization of the standard AFM. Its potential application for ultrahigh storage density has been demonstrated by AFM with a piezoresponse mode to write and read information bits in ferroelectric Pb(Zr(x)Ti(1 - x))O3 films. With this technique, bits as small as 40 nm in diameter have been achieved, resulting in a data storage density of simply more than 200 Gb/in2. Retention loss phenomenon has also been observed and investigated by AFM in the piezoresponse mode. Finally, local piezoelectric measurements of PZT films by different processing technologies are discussed in detail.

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