Michael Sepaniak

Zeigler Professor
Analytical Chemistry

Capillary separations; chemical sensing; laser spectroscopy

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

AAAS Fellow

Additional Information

Group Web Page

Research

Microfluidics. Our current microfluidics (MF) research program is dedicated to the Submicron pillar chip for chemical separations development of capillary electrokinetic lab-on-a-chip separation and sample manipulation techniques for chemical analysis. Fundamental work focuses on studies involving highly ordered assemblies (micelles, cyclodextrins, etc.) as selective reagents for capillary electrophoresis (CE) separations and to expand the versatility of electrophoretic separations. Recently, we have begun using lab-on-a-chip MF separation devices (see figure at right) fabricated using lithographic techniques. The development of new and improved optical detection methods, particularly SERS, 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. Cloning of SERS substrate "cell" Sensitive methods of detection for 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. A major effort involves exploiting the potential for high sensitivity and exceptional selectivity of surface enhanced Raman scattering (SERS) for detection in MF. Approaches have included the use of novel metal-PDMS nanocomposities for integrated MF-SERS. Methods to improve the questionable reproducibility and dynamic range of SERS are being pursued and involve unique lithographically-prepared and nanocomposite substrates to increase sensitivity and dynamic range, and sample translation to improve reproducibility. We have demonstrated for the first time nano-transfer printing and an unusual approach to electron beam lithography that borrows from bio-medically inspired concepts to create unique SERS substrates.

Chemical Sensing. Chemical sensing illustration 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 m-dimension 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 m-cantilevers (see figure at right). The response signatures from arrays of differentially functionalized cantilevers are being used with data mining techniques to identify analytes. The coupling of these arrays with chemical separation techniques is also underway. (graphic: m-cantilevers coated with the enantio-selective antibodies responding (bending) to amino acids; deflections measured by reflecting diode laser beam onto position sensitive detector)

Representative publications

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).

N. A. Abu-Hatab, J. F. Jones and M. J. Sepaniak “Multiplexed Microfluidics-Surface Enhanced Raman Spectroscopy ” Applied Spectroscopy, 61, 1116-1122 (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).

N.A. Hatab and M.J. Sepaniak, “Nanotransfer Printing (nTP) for Surface Enhanced Raman Spectroscopy (SERS)” ACS Nano, 2, 377-385 (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, 1811-1820 (2008).

D. Bhandari, S. M. Wells, S. D. Retterer, and M. J. Sepaniak “Characterization and Detection of Uranyl Ion Sorption on Silver Surfaces using Surface Enhanced Raman Spectroscopy,” Analytical Chemistry 81, 8061-8067 (2009).

S.M.Wells, S.D. Retterer, J.M. Oran, and M.J. Sepaniak “Controllable Nanofabrication of Aggregate-Like Nanoparticle Substrates and Evaluation for Surface Enhanced Raman Spectroscopy,” ACS Nano, 3, 3845-3853 (2009).

N.V. Lavrik, L. Taylor, and M.J. Sepaniak, “ Fabrication of enclosed pillar arrays integrated on a fluidic platform for on-chip separations and analysis”, Lab-on-a-Chip, 10, 1086-1094 (2010).

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.

Border Photo