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Associate Faculty
Department of Pathology
Our research is directed towards developing a
greater understanding of host/material interactions that comprise the
inflammatory cell responses to biomaterials and to acquire fundamental
knowledge and perspective necessary for the design of new materials. A
wide variety of in vitro and in vivo techniques are utilized to study
host/material interactions and these include confocal fluorescence
laser microscopy, cell culture, and the rat cage implant system.
Utilizing silane-modified surfaces, in vitro studies focus on the
material surface dependence of cytokine-induced foreign body giant cell
formation and accompanying cystoskeletal/adhesive structural
reorganization. Studies on the long-term biodegradation of elastomeric
biomaterials are directed toward developing a fundamental understanding
of biocompatibility and biostability/biodegradation of polyurethanes.
Our project on cell adhesion and cytokine release has as its overall
goal the evaluation of the effect of biomedical polymers with varying
surface properties on the activation and cytokine production of
adherent monocytes/macrophages.
Associate Faculty
Department of Chemical
Engineering
Our research focuses primarily on the physical
behavior and processing characteristics of fine particle systems and
colloidal suspensions. We are involved in the development of strategies
that exploit or control the colloidal and interfacial chemistry of the
system to achieve improved processing behavior and ultimately the
enhanced performance of the final materials. Specifically, we are
involved in the development of colloidal engineering strategies for
processing of oxide solids and in fundamental studies of dispersive
mixing phenomena for filled polymer composites. Stability and the
development of morphology in coatings dispersions are also being
studied. In addition, wetting and spreading of liquids on
fine-particles is an ongoing research interest, and novel experimental
approaches to measure these effects are being developed. Recently, we
have begun investigation into simulating and modeling the hydrodynamic,
chemical and mechanical effects that occur in polishing processes
within the microelectronics fabrication industries with the intent of
pointing out process improvements. Finally, we have developed several
methods that use resonant acoustic fields to perform sharp
fine-particle separations with applications in chemical and biochemical
processing.
Steve Hudson
Adjunct Faculty
Ph.D., National Institute of Standards &
Technology, Gaithersburg, MD
Associate Faculty
Department of Chemical
Engineering
Light scattering spectroscopy used to measure
Visco-elastic response of monolayers has been coupled to BAM. This
allows an entirely new set of experiments wherein, for the first time,
measurements of the line tension of monolayer domains are possible.
Applications are to polymer systems. The theory has been developed in
depth. The fundamentals of adhesion are being studied using both a
Digital Instruments AFM and an Image Force Microscope built at Sandia
National Laboratories by J. Houston. Self-assembly and
Langmuir-Blodgett techniques are being used to provide polymer
acid-base surfaces. New work on cell membranes was started during the
year. The light scattering spectra have been studied for
perfect-wetting, binary-mixtures wherein one phase shrinks to a
nanometer thick film with temperature. This provides another method of
determining the Hamaker coefficient that is fundamental to adhesion. We
have started a new project to scale up LB technology for depositing
organized polymer films on very large, high definition, active
liquid-crystal displays. “Classical” methods of spectroscopy and x-ray,
electron diffraction and ellipsometric spectroscopy are used to
characterize the films. In addition a second harmonic microscope is
being assembled that will be used in combination with Brewster angle
microscopy and surface light scattering spectroscopy to characterize
Langmuir and Langmuir Blodgett multilayers of polymer systems.
Associate Faculty
Department
of Biomedical Engineering
Biomimetic materials and biopolymer engineering.
This encompasses self-assembling systems and biomembranes; surface
modification of biomaterials; biomimetic liposomal drug delivery
systems, cell and protein interactions with biomaterials; bacterial
adhesion; and molecular scale imaging and intermolecular force
measurements of plasma proteins and platelets using atomic force
microscopy. On going projects include: Biomimetic Surfactant Polymers as
Biomedical Interface Materials (with E. Anderson and
J. Zhu); Biomimetic Surface Modification for Circulatory Devices (with
S. Wang and K. Kottke-Marchant); Targeted Cell-Selective Liposomal Drug
Delivery (with G. Huang, A. Sen Gupta, Z. Guo, N. Ziats and J. M.
Anderson); Self-Assembled Bis-PNA Monomers As New Biomaterials (with A.
Kumar, S. Sivakova and S.J. Rowan); Surface Interactions of Fibrinogen
and von Willebrand Factor Studied by Atomic Force Microscopy (with R. Srinivasa);
Coagulant Function of Human Aortic Endothelial Cells on
Peptide Surfactant Modified Biomaterials (with J. King, C. Larsen, and K. Kottke-Marchant); Infection
Mechanisms of Cardiovascular Prostheses (with with C. Hofmann and J. M.
Anderson).
Adjunct Faculty
Ph.D., Syracuse Biomaterials Institute, Syracuse University, NY
Associate Faculty
Department of Chemical
Engineering
A colloidal approach has been developed to
prepare homogeneous polymer nanocomposites. Work is in progress on the
rheology of water-based coatings, structure/property relationships in
polymerizable surfactant systems, reactions in microemulsions to obtain
nanoparticles, and high performance clay/polymer nanocomposites. Model
microemulsion systems which exhibit unique features (e.g. thermodynamic
stability and ultralow interfacial tension) were developed. The phase
behavior and solubilization in microemulsions have been modeled.
Microemulsions are characterized using dynamic and electrophoretic
light scattering, electrochemical and other techniques. Microemulsions
are attractive as novel media for polymerization and electrochemistry.
Microporous polymeric solids as well as uniform spherical nanoparticles
are prepared by polymerization of hydrophilic or hydrophobic monomers
solubilized in microemulsions. Hydrophilic-hydrophobic copolymers and
porous composites are obtained from microemulsions. A novel separation
technology using microemulsions as liquid membranes has been developed
for extraction of organics, metal ions and proteins.
Scott Rickert
Adjunct Faculty
Ph.D., NanoFilm LTD.
Associate Faculty
Department
of Physics
During the past year we have continued our work
on nanoscopic patterning of polymer-coated substrates using at atomic
force microscope. By scribing tiny patterns into the polymer and
depositing a liquid crystal on top, we can compel the nematic director
to adopt a well-defined profile that varies on very short length
scales. Pixels as small as a few tens of nanometers are possible, with
each pixel having a unique easy axis. Work in this area involves
studies of phase transitions, wetting phenomena, and development of
optical devices, including a new step-wise Fréedericksz
transition for which one can use simpler addressing schemes in LCDs. A
new thrust was started this year in the area of lamellar liquid
crystals. In collaboration with chemist Carsten Tschierske (Halle,
Germany), we have been examining lamellar-isotropic, lamellar-nematic,
and lamellar-smectic phases. The molecules possess a typical mesogenic
chain, but also possesses a semiperfluroinated side chain that causes
the mesogenic units to segregate into lamellae. In consequence there
exist quasi-two-dimensional analogs to the three dimensional liquid
crystalline phases. Initial results indicate that the twist elasticity
is more than an order of magnitude smaller than for a 3D nematic due to
the large interlamellar separation.
Associate Faculty
Department
of Physics
Our research focuses on optoelectronic and
electronic properties of organic materials. Current projects focus in
the areas of organic semiconducting materials and nonlinear optical
materials. We are investigating self-assembled and other
photoconducting polymers for photorefractive, photovoltaic and other
optoelectronic applications. In particular, we are focusing on enhanced
carrier mobility in discotic columnar and smectic liquid crystals
arising from the enhanced order compared with amorphous polymer
materials, as well as enhance mobility due to cross-linked conjugated
networks in polymers. We are also investigating paths to optimizing the
second order nonlinear optical response in chiral media. We have
characterized candidate molecular species by hyper-Rayleigh scattering,
developed a simple quantum model, and are investigating schemes for
producing ordered chiral media to exploit these nonlinear optical
responses. We are investigating supramolecular chiral nonlinear optics
responses. Finally, we are studying nonlinear optical
responses in liquid crystals due to surface mediated charge
interactions.
Associate Faculty
Department
of Electrical Engineering and Computer Science
Molecular electronics, molecular batteries,
nano-technology tools for molecular scale electrical, microwave and
optical measurements, emerging bio and quantum computation techniques,
and electronic/optical devices. Novel sensors and actuators, and
neuromorphic signal processing for massive sensor fusion data.
Microwave and conducting atomic force microscopy for non-destructive
and non-intrusive characterization of materials and devices.
Computational and network hierarchy for molecular circuits.
Input/output mechanisms in molecular circuits. Quantum computation
devices and networks.
Associate Faculty
Department
of Physics
One recent focus of research has been the nature
of the glass transition in polymeric materials. We study the glass
transition in syndiotactic PMMA through atomistic molecular dynamics
simulations. The mean squared deviations of atoms, monomers, and
molecules from their initial positions are analyzed by means of a
technique that separates the effects of diffusive motion from the
underlying vibrational motion. The diffusive motion shows a power-law
variation with time, with an exponent that varies continuously from 0.5
below the glass transition temperature, Tg, to 1 at high temperatures.
The self part of the van Hove correlation functions for both hydrogen
atoms and monomers shows structural arrest at the lowest temperature
studied. A second peak in the atomic van Hove correlation can be
attributed to rotation of the CH3 group. The diffusion of solvents into
polymers often causes swelling, and may lead the polymer to pass from
the glassy to the rubbery state. However, this process is extremely
slow, and has seemed to be inaccessible to simulation using
molecular-dynamics techniques. We explore the technique of adjusting
the partial charges on the solvent material in order to control the
speed of the diffusion process. By completely removing the partial
charges on the methano we are able to achieve our objective of studying
the diffusion of this modified methanol into poly(methyl methacrylate)
in a reasonable computational time. We find penetration of methanol
into PMMA to be accompanied by swelling, an increase in radius of
gyration of the PMMA molecules of about 7 percent, and an increase in
mean squared displacement of the constituent atoms of the PMMA
indicative of plasticization. In other work we have explored the
interaction between the surface of an amorphous polymer and a nematic
liquid crystal. This research involved both molecular modeling and
analytical analysis of the classical equations of motion of the polymer
and liquid crystal.
Associate Faculty
Department of Chemical
Engineering
Fuel cells, transport and electrochemistry in
energy conversion and storage devices, NMR spectroscopy and imaging,
transport/structure property relationships in polymer electrolytes, and
self-assembly chemistry.
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