Biomedical subjects

Jae Youn Lee

Publications and source records attributed to Jae Youn Lee.

4 recordsLinked to original sources

PubMed2004

Using nanoparticles to create self-healing composites.

The need for viable materials for optical communications, display technologies, and biomedical engineering is driving the creation of multilayer composites that combine brittle materials, such as glass, with moldable polymers. However, crack formation is a critical problem in composites where thin brittle films lie in contact with deformable polymer layers. Using computer simulations, we show that adding nanoparticles to the polymers yields materials in which the particles become localized at nanoscale cracks and effectively form "patches" to repair the damaged regions. Through micromechanics simulations, we evaluate the properties of these systems in the undamaged, damaged, and healed states and determine optimal conditions for harnessing nanoparticles to act as responsive, self-assembled "band aids" for composite materials. The results reveal situations where the mechanical properties of the repaired composites can potentially be restored to 75%-100% of the undamaged material.

Journal Article↗

PubMed2003

Modeling the self-assembly of copolymer-nanoparticle mixtures confined between solid surfaces.

Using numerical calculations, we undertake the first morphological studies of mixtures of AB diblocks and nanoparticles that are confined between two hard walls. A complex interplay of entropic and enthalpic interactions drives the nonselective particles to localize at the hard walls and A/B interfaces, causing the mixture to spontaneously self-assemble into particle-decorated lamellae that are oriented perpendicular to the surfaces. The film reveals a periodic array of particle "nanowires" that are separated by the nanoscale polymer domains, yielding a vital material for nanodevice fabrication.

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PubMed2003

Self-assembly of a binary mixture of particles and diblock copolymers.

Using theoretical models, we undertake the first investigation into the synergy and rich phase behavior that emerges when binary particle mixtures are blended with microphase-separating copolymers. We isolate an example of spontaneous hierarchical self-assembly in such hybrid materials, where the system exhibits both nanoscopic ordering of the particles and macroscopic phase transformation in the copolymer matrix. Furthermore, the self-assembly is driven by entropic effects involving all the different components. The results reveal that entropy can be exploited to create highly ordered nanocomposites with potentially unique electronic and photonic properties.

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PubMed2002

Binary hard sphere mixtures in block copolymer melts.

We perform a self-consistent-field/density-functional-theory hybrid analysis for a system of diblock copolymers mixed with polydisperse, hard, spherical particles of various chemical species. We apply this theory to study the equilibrium morphologies of two different binary sphere/diblock melts. First, we examine the case where the particles have two different sizes, but both types are preferentially wetted by one of the copolymer blocks. We find that the single-particle distributions for the two species do not track one another and that the particles show a degree of entropically generated separation based on size, due to confinement within the diblock matrix. Second, we study the case where the particles are all the same size, but are of two different chemical species. We find that, as expected, the particle distributions reveal a degree of enthalpically driven separation, due to the spheres' preferential affinities for different blocks of the copolymer.

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