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Biomedical subjects

Nianqiang Wu

Publications and source records attributed to Nianqiang Wu.

5 recordsLinked to original sources
PubMed2006

Directed fabrication of radially stacked multifunctional oxide heterostructures using soft electron-beam lithography.

A versatile patterning approach based on electron-beam lithography (eBL) and solution deposition, termed soft-eBL, has been developed to fabricate radially stacked heterostructures of multifunctional oxides from their sol precursors. Well-defined nanorings of lead zirconate titanate (PZT) are fabricated on a variety of substrates such as noble metals (e.g., Au), semiconductors (e.g., Si), and oxide single crystals (e.g., SrTiO3), which were previously functionalized with appropriate self-assembled monolayers (SAMs). The undercut in the double-layer eBL resist and substrate functionalization with the SAM treatment play a vital role in the formation of the ring structures. The nanorings are then used as building block "containers" and ring-reservoirs are filled with a second sol (e.g., CoFe2O4) to form radially stacked composite ceramic heterostructures. The approach presented here does not require either feature alignment to realize heterostructures or the etching of ceramics, and is amenable to a variety of radially stacked composite heterostructures.

Crystallization↗
PubMed2005

Transport of organic solutes through amorphous teflon AF films.

Fluorous media have great potential for selective extraction (e.g., as applied to organic synthesis). Fluorous polymer films would have significant advantages in fluorous separations. Stable films of Teflon AF 2400 were cast from solution. Films appear defect-free (SEM; AFM). Rigid aromatic solutes are transported (from chloroform solution to chloroform receiving phase) in a size-dependent manner (log permeability is proportional to -0.0067 times critical volume). Benzene's permeability is about 2 orders of magnitude higher than in comparable gas-phase experiments. The films show selectivity for fluorinated solutes in comparison to the hydrogen-containing control. Transport rates are dependent on the solvent making up the source and receiving phases. The effect of solvent is, interestingly, not due to changes in partition ratio, but rather it is due to changes in the solute diffusion coefficient in the film. Solvents plasticize the films. A less volatile compound, -COOH-terminated poly(hexafluoropropylene oxide) (4), plasticizes the films (T(g) = -40 degrees C). Permeabilities are decreased in comparison to 4-free films apparently because of decreased diffusivity of solutes. The slope of dependence of log permeability on critical volume is not changed, however.

Benzene↗
PubMed2005

Facile scheme for fabricating solid-state nanostructures using e-beam lithography and solution precursors.

We demonstrate a facile approach for site-specific fabrication of organic, inorganic, and hybrid solid-state nanostructures through a novel combination of electron-beam lithography (eBL) and spin coating of liquid and sol-gel precursors, termed soft eBL. By using eBL patterned resists as masks in combination with a low cost process such as spin coating, directed growth of nanostructures with controlled dimensions is achieved without the need for the costly and difficult process step of etching ceramics. The highly versatile nature of the scheme is highlighted through the fabrication of nanostructures of a variety of materials such as ferroelectric, optoelectronic, and conducting polymeric materials at different length scales and spatial densities on a multitude of substrates.

Journal Article↗