Biomedical subjects

Gareth H McKinley

Publications and source records attributed to Gareth H McKinley.

4 recordsLinked to original sources

PubMed2006

High-performance elastomeric nanocomposites via solvent-exchange processing.

The incorporation of nanoparticles into engineering thermoplastics affords engineers an opportunity to synthesize polymer nanocomposites that potentially rival the most advanced materials in nature. Development of these materials is difficult because thermodynamic and kinetic barriers inhibit the dispersal of inorganic, often hydrophilic nanoparticles in hydrophobic polymer matrices. Using a new solvent-exchange approach, we preferentially reinforce the hard microdomains of thermoplastic elastomers with smectic clay of similar characteristic dimensions. The strong adhesion between the clay and the hard microdomains coupled with the formation of a percolative network not only stiffens and toughens, but increases the heat distortion temperature of the material and induces reversible thermotropic liquid-crystalline transitions. The discotic clay platelets induce morphological ordering over a range of length scales, which results in significant thermomechanical enhancement and expands high-temperature applications. Merging block-copolymer processing techniques with this method for preferential ordering of nanoparticle facilitates the development of new, hierarchically ordered materials.

Elastomers↗

PubMed2006

Inductively heated shape memory polymer for the magnetic actuation of medical devices.

Presently, there is interest in making medical devices such as expandable stents and intravascular microactuators from shape memory polymer (SMP). One of the key challenges in realizing SMP medical devices is the implementation of a safe and effective method of thermally actuating various device geometries in vivo. A novel scheme of actuation by Curie-thermoregulated inductive heating is presented. Prototype medical devices made from SMP loaded with nickel zinc ferrite ferromagnetic particles were actuated in air by applying an alternating magnetic field to induce heating. Dynamic mechanical thermal analysis was performed on both the particle-loaded and neat SMP materials to assess the impact of the ferrite particles on the mechanical properties of the samples. Calorimetry was used to quantify the rate of heat generation as a function of particle size and volumetric loading of ferrite particles in the SMP. These tests demonstrated the feasibility of SMP actuation by inductive heating. Rapid and uniform heating was achieved in complex device geometries and particle loading up to 10% volume content did not interfere with the shape recovery of the SMP.

Biocompatible Materials↗

PubMed2005

Controlling the location and spatial extent of nanobubbles using hydrophobically nanopatterned surfaces.

The presence of nanobubbles-as imaged with tapping-mode atomic force microscopy-is controlled using nanopatterned surfaces possessing repeating patterns of polystyrene (hydrophobic domains) and poly(methyl methacrylate) (hydrophilic domains). For nanobubbles to be present, we find that, in addition to controlling the degree of surface hydrophobicity, it is important for the spatial dimensions of the hydrophobic domains on the nanopatterned surface to be commensurate with the equilibrium topology of the nanobubbles.

Journal Article↗

PubMed2003

Microscopic and macroscopic structure of the precursor layer in spreading viscous drops.

We study the spreading of viscous nonvolatile liquids on smooth horizontal substrates using a phase-modulated interference microscope with sufficient dynamic range to enable the simultaneous measurement of both the inner ("microscopic") length scale and the outer ("macroscopic") flow scale in addition to the intermediate matching region. The resulting measurements of both the apparent contact angle and the lateral scale of the precursor "wetting" film agree quantitatively with theoretical predictions for a van der Waal's liquid over a wide range of capillary numbers.

Journal Article↗