2007 - Chemical & Biomedical Engineering - University of South ...

Dr. Ryan G. Toomey
Assistant Professor
rtoomey@eng.usf.edu
(813) 974-1964
Education:
Post-Doctoral Research, Institute for Microsystems Technology (IMTEK). University of
Freiburg, Germany, 2002-2003
Ph.D in Chemical Engineering, University of Minnesota, Minneapolis, 2002
B.S. in Chemical Engineering, University of California, Berkeley, 1995
Research Interests: Polymeric Materials, Interfacial Phenomena, Molecular
Recognition, Hydrogels
Smart Polymer Structures for Microfluidics
Our research program is to design and develop micro-scale polymeric
structures that experience changes in shape and other properties when
triggered by an external stimulus. These materials can significantly
advance the capability of microfluidics and miniature biosensors, for
they operate without complex circuitry or bulky instrumentation. For
instance, Figure 1 shows a cell sheet on a smart surface. The surface
can either be “turned on” or “turned off” to support or release cells. In
the image, the surface has been turned off and the cell sheet, which
was cultured on the surface, detaches and rolls off. Figure 2 shows E.
Coli. (green) that has been sequestered and pinched off from an
overhead solution using smart polymers (shown in red). These
polymer patterns are currently being explored to separate bacteria
from blood for sample processing in biosensors. This research is highly
collaborative and is carried out in conjunction with Dr. Peter Stroot
(Civil and Environmental Engineering, USF) and Dr. Jing Wang
(Electrical Engineering, USF).
Recent Publications:
Toomey, R. and Tirrell, M. “Functional
Polymer Brushes in Aqueous Media from
Self-Assembled and Surface-Initiated
Polymers” Annual Review of Physical
Chemistry In press (2008).
Vidyasagar, A., Majewski, J., and
Toomey, R. “Temperature induced
volume-phase transitions in surfacetethered
Poly(N-isopropylacrylamide)
networks” Macromolecules (2008).
41:3, p.919-924.
Castellanos, A., DuPont, S., Heim, A.,
Matthews, G., Stroot, P., Moreno, W.,
Toomey, R. “Size-exclusion "capture
and release” separations using surfacepatterned
poly(N-isopropylacrylamide)
hydrogels” Langmuir (2007). 23:11, p.
6391-6395.
Alonzo, J., Huang, Z., Liu, M., Mays, J.,
Toomey, R., Dadmun, M., Kilbey S.
“Looped Polymer Brushes Formed by
Self-assembly of Poly(2-vinylpyridine)-
polystyrene-poly(2-vinylpyridine)
Triblock Copolymers at the Solid-fluid
Interface. Kinetics of Preferential
Adsorption.” Macromolecules (2006)
39:24, p.8434-8439.
Figure 1. Cultured cell sheet released from a smart polymer (poly-Nisopropylacrylamide)
surface. Photo taken by Ophir Ortiz.
The approach is to use stimuli-responsive, polymer films that toggle
the adsorption of specific targets in response to a stimulus. The
stimulus could be temperature, pH, or a small analyte, which induces a
change in the surface energy of the cross-linked layer. The response
characteristics are built directly into the polymer structure, and
therefore a separateu feedback loop is not required. Ultimately, we
would like to use these materials to exploit subtle differences in the
binding affinities of macromolecules and proteins for “bind and release”
separations without having to resort to biological recognition. While
fully natural or biological surfaces impart the highest level of
specificity, they also lack stability in non-native environments. Our
goal is to bring a level of recognition to responsive synthetic materials.
In our current work, we addressing two main points:
Figure 1. E. Coli. (green) sequestered
between smart polymer monoliths
(red).Photo by Samuel DuPont.
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