Michael Sepaniak

Zeigler Professor
Analytical Chemistry

Capillary separations; chemical sensing; laser spectroscopy

B.S., Northern Illinois University (1974)
Ph.D., Iowa State University (1980)

Additional Information

Group Web Page

Research

Microscale Chemical Separations. Our separations research program is dedicated to the development of capillary electrokinetic separation techniques for chemical analysis. Fundamental work focuses on studies involving highly ordered assemblies as selective reagents for capillary electrophoresis (CE) separations. These additives have included macrocyclic compounds such as cyclodextrins (CDs) and calixarenes, micelles, and soluble (entangled) polymers and are employed in electrophoretic (e.g., CE) or electrochromatographic (e.g., micellar electrokinetic capillary electrochromatography) modes. An important goal of our work is to study molecular recognition as it applies to CE separations using molecular modeling techniques. Recently, we have begun using lab-on-a-chip microfluidic separation devices fabricated from polymeric materials such as polydimethylsiloxane (PDMS). The development of new and improved optical detection methods is also a focus of our efforts (see below). Our separations work is applied to samples of environmental, forensic, biological, and industrial significance.

Optical Spectroscopy. Sensitive methods of detection for CE and lab-on-a-chip devices are being developed based on laser optical methods. The inherent sensitivity of laser induced fluorescence detection has been exploited for a wide variety of applications (naturally fluorescent drugs, toxins, labeled DNA and proteins, metal complexes, etc.). A major effort involves exploiting the potential for high sensitivity and exceptional selectivity of surface enhanced Raman scattering (SERS) for detection in microscale separations. Approaches have included on-column detection using running buffers containing silver colloid, off-column detection following deposition onto planar substrates, and the use of novel metal-PDMS nanocomposities for integrated microfluidics and SERS detection. Methods to improve the questionable reproducibility and dynamic range of SERS are being pursued and involve unique lithographic and nanocomposite substrates to increase sensitivity and dynamic range, sample translation to improve reproducibility, and applications in separations, high throughput screening, and sensing (see below).

Chemical Sensing. Methods to impart selectivity to micro-electro-mechanical sensors (MEMS) are being developed. Methods of depositing and immobilizing polysiloxane phases, chelating resins and imprinted sol gels, and macrocylic reagents on microdimension cantilever-based MEMS are being developed. The macrocycle compounds developed and characterized through molecular recognition studies serve as tunably selective sequestering phases when immobilized on the planar substrate. These various phases are used to increase response factors and add chemical specificity to analyte-induced surface stresses that cause the cantilevers to bend. Methods of developing nano-structured surface features enhance the response characteristics of the sensors by orders of magnitude. Applications for these novel sensing technologies abound in the environmental, homeland security, and medical fields. For example, chiral discrimination has been achieved by immobilizing antibodies on microcantilevers. In some cases the responses of the nano-structured cantilevers has been so large that the possibility of using the devices as actuator in the development of chemi-mechanical transistors has been envisioned. Fiberoptic sensors based on SERS are also under development. Distributed selectivity is sought using spatially patterned chemically selective phases (e.g., molecularly imprinted polymers) on fiberoptics over-coated with lithographically prepared SERS surfaces.

Representative publications

P.J. Chapman, P. Dutta, P.G. Datskos, G.L. Devault, and M.J. Sepaniak, "Facile Hyphenation of Gas Chromatography and Microcantilever Array Sensor for Enhanced Selectivity in VOC Mixture Analysis," Analytical Chemistry, 79, 364-370 (2007) .

P. Dutta, K.L. Hill, P.G. Datskos, and M.J. Sepaniak, "Development of a Nanomechanical Biosensor for Analysis of Endocrine Disrupting Chemicals" Lab-on-a-Chip, 7, 1184-1191 (2007) .

R.M. Connatser and M.J. Sepaniak, "Analytical Optimization of Microfluidic Separation Devices with Integrated Nanocomposite SERS Detection Regions," Electrophoresis, 29, 1441-1450 (2008) .

J.M. Oran, N.A. Hatab, R.J. Hinde, S. Retetter, and M.J. Sepaniak, "Nanofabricated Periodic Arrays of Silver Elliptical Disks as SERS Substrates," J. Raman Spectroscopy., 39, 1130-1139 (2008) .

N.A. Hatab and M.J. Sepaniak, "Nanotransfer Printing for Surface Enhanced Raman Spectroscopy" ACS Nano, 2, 377-385 (2008) .

Biographical sketch

Dr. Sepaniak received his B.S. in Chemistry from Northern Illinois University in 1974 and his Ph.D. in Analytical Chemistry from Iowa State University in 1980. He joined the faculty of the University of Tennessee in 1981 and has been affiliated with Oak Ridge National Laboratory throughout his time at Tennessee. He is a former Head of the Department of Chemistry and is a Paul and Wilma Ziegler Professor of Chemistry.

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