Magnetic Resonance in Microfluidics
Microfluidic devices are revolutionizing medical diagnostics, forensics, and other fields of chemistry and biology. We are working toward seamless integration of NMR spectroscopy as well as imaging (MRI) into microfluidic environments.Our efforts focus on visualization of flow phenomena and flow control in microfluidic chips, as well as efficient coupling of the microchip to the NMR receiver system. (In collaboration with James Landers, Chemistry, U.Va., and Matthew. R. Begley, MAE, U.Va.)
Polyelectrolyte Hydrogels as Mechanical Transducers
Polyelectrolytes are polymers that contain charged groups on their backbone. Cross-linked networks of such polymer chains can swell in water and other solvents by impressive amounts. Due to the very different dynamics of the ions attached to the polymer and the (necessarily present) small, free counterions, such swollen gels have unique properties that make them interesting as electro-mechanical transducers. We are using a combination of electrochemical techniques, mechanical testing, and advanced NMR spectroscopy to study the interplay between transport processes and the electromechanical transduction properties of such materials, in view of applications in microfluidic diagnostic devices.
Chemo-Mechanical Interactions For Nano-Sensors
(In collaboration with Prof. Matthew Begley and Prof. James Landers, University of Virginia) Molecular species adsorbing onto the surface of a mechanical system can produce measurable deflections, if the interaction energies between the adsorbed groups and the energy required to deform the system are of comparable magnitude. We are investigating, both experimentally and theoretically, the possibility to use this effect for ultra-sensitive, low-cost detection of molecular species. In particular, we are interested in applications of such sensors in the context of microfluidic devices.
Nuclear Magnetic Resonance Techniques For Polymers
The structural characaterization of polymer solids is difficult, since they often lack long-range translational order. This produces severe difficulties for scattering techniques, and often prevents the extraction of true molecular information from diffraction patterns. NMR spectroscopy, by contrast, can potentially give highly specific structural information. However, the NMR method applied must be taylored to the problem under study. We are continually working on optimized NMR methods that help us in our research efforts towards understanding the mechanical and transport properties of polymer materials.
Localization Of Plastic Deformation Events in Glasses
The plasticity of glasses is a perplexing problem of materials science. It is clear that localized processes must be responsible for the surprising ductility of materials such as polycarbonate, but little is known about their exact nature and length scale. Using a combination of mechanical testing, molecular computer simulation, and NMR spectroscopy, we are working towards fundamental understanding of the large-strain mechanical properties of polymer glasses.
Characterization of Structural Disorder in Amorphous Organic Semiconductors by Solid-State NMR
(In collaboration with Prof. Fotios Papadimitrakopoulos, University of Connecticut) Organic Semiconductor materials are often used in the form of amorphous thin films. The molecular packing in such films is known to have a critical influence on the photo-electrical properties of the system, but is notoriously hard to characterize. We have used liquid-state exchange NMR spectroscopy to characterize the intra-molecular dynamics of the organic semiconductor Aluminum tris(quinoline-8-olate), aka Alq3. Using solid-state 27Al NMR, we were able to distinguish between different molecular conformations in the solid state. This could then be exploited to characterize the structural disorder in amorphous thin films of Alq3.
Recent Publications
