Biomedical subjects

Pil J Yoo

Publications and source records attributed to Pil J Yoo.

8 recordsLinked to original sources

PubMed2006

Virus-enabled synthesis and assembly of nanowires for lithium ion battery electrodes.

The selection and assembly of materials are central issues in the development of smaller, more flexible batteries. Cobalt oxide has shown excellent electrochemical cycling properties and is thus under consideration as an electrode for advanced lithium batteries. We used viruses to synthesize and assemble nanowires of cobalt oxide at room temperature. By incorporating gold-binding peptides into the filament coat, we formed hybrid gold-cobalt oxide wires that improved battery capacity. Combining virus-templated synthesis at the peptide level and methods for controlling two-dimensional assembly of viruses on polyelectrolyte multilayers provides a systematic platform for integrating these nanomaterials to form thin, flexible lithium ion batteries.

Bacteriophage M13↗

PubMed2006

Spontaneous assembly of viruses on multilayered polymer surfaces.

The idea that randomly arranged supermolecular species incorporated in a network medium can ultimately create ordered structures at the surface may be counterintuitive. However, such order can be accommodated by regulating dynamic and equilibrium driving forces. Here, we present the ordering of M13 viruses, highly complex biomacromolecules, driven by competitive electrostatic binding, preferential macromolecular interactions and the rigid-rod nature of the virus systems during alternating electrostatic assembly. The steric constraints inherent to the competitive charge binding between M13 viruses and two oppositely charged weak polyelectrolytes leads to interdiffusion and the virtual 'floating' of viruses to the surface. The result is the spontaneous formation of a two-dimensional monolayer structure of viruses atop a cohesive polyelectrolyte multilayer. We demonstrate that this viral-assembled monolayer can be a biologically tunable scaffold to nucleate, grow and align nanoparticles or nanowires over multiple length scales. This system represents an interface that provides a general platform for the systematic incorporation and assembly of organic, biological and inorganic materials.

Acrylic Resins↗

PubMed2006

Formation of regular nanoscale undulations on a thin polymer film imprinted by a soft mold.

We observed the formation of regular nanoscale undulations on a polystyrene film when imprinted by a soft poly(dimethylsiloxane) mold above the polymer's glass transition temperature. The shape of the wave was reminiscent of a buckling wave frequently observed for a metal film supported on an elastomeric substrate. We derived a simple theoretical model based on an anisotropic buckling of the polymer film rigidly bound to a substrate, which agrees well with the experiment.

Journal Article↗

PubMed2004

Solvent-driven dewetting and rim instability.

An experimental method suitable for reproducible results has been used to investigate dewetting behavior of thin films of solvent-laden polymer. This solvent-driven dewetting enables one to change spreading coefficient by an order of magnitude that is not readily realizable in thermal dewetting and to study polar interactions that have not been fully exploited experimentally. While the film instability is similar to that found in thermal dewetting, the rim instability is quite different. Two different types of the rim instability have been found. With a polar solvent, the rim instability changes from one type to another with increasing film thickness whereas the unstable rim becomes stable for an apolar solvent.

Journal Article↗

PubMed2004

Polymer elasticity-driven wrinkling and coarsening in high temperature buckling of metal-capped polymer thin films.

We report the critical effects the deformational stress from the elastic nature of a confined polymer layer has during the relaxation process on the buckling of thin metal-polymer bilayer systems (less than 100 nm) even above the temperature at which the polymer is in the liquid flow region. In contrast with what is generally believed, the dispersion force does not play a significant role in the buckling. We also find that the final wrinkled waves take on the shape of wormlike islands. The coarsening leading to the island structure is driven by the growth in amplitude of the dominant wave at the expense of less dominant ones.

Journal Article↗

PubMed2004

An ultraviolet-curable mold for sub-100-nm lithography.

We describe a novel UV-curable mold that is stiff enough for replicating dense sub-100-nm features even with a high aspect ratio. It also allows for flexibility when the mold is prepared on a flexible support such that large area replication can be accomplished. The composite material of the mold is inert to chemicals and solvents. The surface energy is made low with a small amount of releasing agent such that the mold can be removed easily and cleanly after patterning. In addition, the material allows self-replication of the mold. These unique features of the mold material should make the mold quite useful for various patterning purposes.

Journal Article↗

PubMed2004

Patterning and separating infected bacteria using host-parasite and virus-antibody interactions.

Bacteria were selectively deposited on substrates patterned with poly(ethylene glycol) (PEG) microstructures by using host-parasite and virus-antibody interactions. In this scheme viruses were used to attach onto a host bacterium, Escherichia coli (E. coli). The E. coli expressing the virus were selectively adhered to the regions pretreated with an antibody against the virus proteins while E. coli without the virus showed no selectivity. Single or aggregated cell arrays were fabricated depending on the initial pattern size with respect to the size of E. coli. The current approach could be a general route to spatially positioning or controlling adhesion of other biological species that are not accessible by conventional methods and as a tool for separating and isolating specific cell populations based on host-parasite interactions.

Antibodies, Viral↗

PubMed2003

Evolution of a stress-driven pattern in thin bilayer films: spinodal wrinkling.

We report the full spectrum of the evolution of the wrinkle pattern formation in a thin bilayer film of an elastic metal on a viscoelastic polymer. Although the origin is different, the transition of an initial islandlike pattern to a labyrinthine structure without any change in the wavelength (q approximately t(0)) and the overall evolutionary process is strikingly similar to that in the spinodal system but the process is robust and takes place on a long time scale (about 10 days). The change into a mountainous topography in the late stages is accompanied by an increase in the length scale from an initial wavelength to another. This change, due to the relaxation of the confined polymer that results in a transition from elastic- to viscouslike behavior, induces wave coarsening (q approximately t(-1.04+/-0.08)) and macroscopic roughening.

Journal Article↗