 Gary E. Wnek
p>Ph.D., University of Massachusetts, Amherst
Joseph F. Toot, Jr., Professor of Engineering
email: gew5@case.edu
office: A.W. Smith, Room 124B
tel: (216) 368-2728
Research
1. Polymers
in Medicine
Over the past several years, we have been
involved in the development of electrostatic spinning (electrospinning) as a
method of fabrication of scaffolds for tissue engineering, drug delivery, and
related applications. The motivation is
to create bio-mimicking fibers in a diameter range (ca. 20-100 nm) difficult to
access by conventional fiber processing methods. Our group's long-term focus is
directed toward exploitation of nanofiber scaffolds for a better understanding
of processes in the central nervous system or CNS (the brain and spinal cord),
and ultimately to contribute to restoration of function impaired by CNS-related
diseases. We believe that much can be learned about fundamental cellular
processes if cells are presented with the appropriate 3-D scaffold on which to
grow, proliferate, and communicate. We are also interested in the development
of platforms for cell encapsulation and, longer term, the fabrication of
'artificial cells.' Toward that end, attention is being directed toward the
construction of novel bio-fuel cells.
2. Polymers
in Electrochemical Devices: Fuel Cells and Batteries
A growing interest exists in the development of
new materials with improved properties for various energy storage and conversion
devices, including batteries, fuel cells, and supercapacitors. Over the past 10
years, our group has helped to develop new, low-cost proton-conducting membranes
based on simple random and block copolymer structures containing partially
sulfonated styrene units. We learned a great deal about the influence of ionic
aggregation and morphology in these materials, and are beginning to apply this
knowledge to the design of new polymers with, for example, low permeation to
methanol for use in direct methanol fuel cells. In addition, we are exploring
the use of these and other polymer electrolytes as hosts for luminescent dyes
for the development of electroluminescent devices with tunable emission
profiles.
We have recently embarked on a program to
exploit electrostatic processing, specifically electrospraying and
electrospinning as a general approach for the fabrication of electrochemical
devices, particularly fuel cells and batteries. A typical proton exchange
membrane fuel cell, for example, has as its principal components a
proton-conducting membrane, anode and cathode electro-catalyst layers with
specific compositions and porosities, and a porous and conductive gas diffusion
layer to allow good access of hydrogen and oxygen to the electrodes. We propose
that this entire device, termed a membrane-electrode assembly, can be fabricated
by electroprocessing.
We have demonstrated to date that the
prototypical proton-conducting membrane, Nafion, can be electrosprayed and has
electrical properties identical to that of commercial films. We are now
developing electrode compositions for electrospraying, to be shortly followed by
electrospinning of gas diffusion layers. Attention is also being directed to
fabrication of Li battery components by electroprocessing, including gel
electrolytes and metal oxide cathodes.
3.
Microfluidics and Sensors
We have helped to develop a new approach to
'lab-on-a-chip' microfluidic devices based on 2-D printing of hydrophilic paths
on otherwise hydrophobic surfaces and bringing two such surface in close
proximity without actual contact. Water will wet the hydrophilic paths and be
drawn along them by capillary action, yet the sidewalls are in contact with air
and thus the water channels are confined by the fluid's surface tension. An
attractive feature of this approach is that all paths can be easily printed on
inexpensive materials rather than inscribed as 3-D channels as is the case with
conventional microfluidic devices. Another attribute is that reactive reagents
can be 'spotted' along the paths by printing, affording a simple means to
fabricate complex assay systems.
Our group is also developing impedance-based
sensors for live cell cultures, building on the work on electric cell-substrate
impedance sensing (ECIS) by Giaever and Keese at RPI. Our focus is sensing in
3-D cell cultures that better mimic the natural environment of cells and
tissues, and we have developed a system using thin (ca. 2-10
mm)
gold wires in fibrin gels that is the subject of a paper in preparation. The
gold wire diameters are similar to those of many mammalian axons, and we plan to
focus on the notion of using the wires as artificial axon templates for neural
cell growth, with specific attention toward understanding biochemical triggers
of myelination and demyelination, the latter being associated with
neurodegenerative diseases such as multiple sclerosis.
Selected Publications
G. E. Wnek, M. E.
Carr, D. G. Simpson and G. L. Bowlin, “Electrospinning of Nanofiber Fibrinogen
Structures,” Nano Lett., 3, 213-216 (2003)
L. Yao, T. W. Haas,
A. Guiseppi-Elie, G. L. Bowlin, D. G. Simpson, and G. E. Wnek, “Electrospinning
and Stabilization of Fully Hydrolyzed Poly(vinyl alcohol) Fibers,” Chem.
Mater, 15, 1860 (2003)
E.-R. Kenawy, J. M.
Layman, J. R. Watkins, G. L. Bowlin, J. A. Matthews, D. G. Simpson
and G. E. Wnek, “Electrospinning of Poly(Ethylene-co-Vinyl Alcohol) Fibers,”
Biomaterials, 24, 907-913 (2003)
E. H. Sanders, R.
Kleofkorn, G. L. Bowlin, D. G. Simpson and G. E. Wnek, “Two-Phase
Electrospinning from a Single Electrified Jet: Microencapsulation of Aqueous
Reservoirs in Poly(Ethylene-co-Vinyl Acetate) Fibers,” Macromolecules,
36, 3803 (2003)
E. H. Sanders, K. A.
McGrady, G. E. Wnek, C. A. Edmonson, J. M. Mueller, J. J. Fontanella, S. Suarez
and S G. Greenbaum, "Characterization of Electrosprayed Nafion Films," J.
Power Sources, 129, 55 (2004)
E. D. Boland, K. J.
Pawlowski, D. G. Simpson, G. E. Wnek and G.L. Bowlin. "Electrospinning
Collagens and Elastin: Preliminary Vascular Tissue Engineering." Frontiers in
Biosciences, 9, 1422 (2004)
D. L. Woerdeman,
P. Ye, S. Shenoy, R. S. Parnas, G. E. Wnek, and O. Trofimova, “Electrospun
Fibers from Wheat Protein: Investigation of the Interplay between Molecular
Structure and the Fluid Dynamics of the Electrospinning Process,”
Biomacromolecules, 6,
707 (2005)
S.L. Shenoy, H. L. Frisch,
W. D. Bates and G. E. Wnek, "Role
of Chain Entanglements on Fiber Formation During Electrospinning of Polymer
Solutions: Good Solvent, Non-Specific Polymer-Polymer Interaction Limit,"
Polymer, 46, 3372 (2005)
O.
A. Baturina and G. E. Wnek, “Characterization of PEM Fuel Cells with Catalyst
Layers Obtained by Electrospraying,” Electrochem.
Solid State Lett.,
8,
A267 (2005)
G. E. Wnek and S. G. Cort,
“Product and Process Design and Delivery: Invention Through to Innovation,”
Proc. ASEE Annual Conference and Exposition, Portland,OR, June 2005
S.
L. Shenoy. W. D. Bates and G. E. Wnek,
“Correlation Between
“Electrospinnability” and Physical Gelation,” Polymer, in press
Edited Work
G. E. Wnek and G. L.
Bowlin, eds., Encyclopedia of Biomaterials and Biomedical Engineering,
Vols. 1 and 2, Marcel Dekker, New York (2004)
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