Our current research interests focus on the modeling, design, and development of chemical sensors and sensor arrays for monitoring simple organic molecules in air and biological media; the implementation of sensor-based systems for environmental monitoring applications; and the development of integrated microanalytical systems for complex vapor-mixture analysis.
In the area of chemical sensors, our group has focused primarily on microsensors that utilize surface-acoustic-wave propagation through small piezoelectric substrates, whose responses arise from changes of mass or elastic stiffness in deposited interfacial films. Complementary sensor technologies, such as chemiresistors, which respond to changes in the dielectric properties of the interface material, are also being developed. Investigations have involved the synthesis of novel chemically selective interface (coating) materials, elucidation of the mechanisms by which the interfacial films interact with gas-phase analytes, development of predictive sensor response models, chemometric pattern recognition methods and artificial neural networks to aid in decoding sensor array response patterns, and construction of practical sensor-based instrumentation. Integration of these sensors with other micromachined components to create miniaturized ("on-chip") analytical systems employing novel valve, pump, preconcentrator, separation, and sensor-array designs is also being actively explored through collaborations in the Center for Wireless Integrated Microsystems (www.eecs.umich.edu/wims).
Among the sensor interface materials examined are Au-thiolate nanoclusters, organometallic complexes capable of facile ligand-exchange reactions, electrically conducting polymers, side-chain liquid-crystalline polymers capable of subtle size/shape selectivity, and various functionalized isotropic polymers. We are also exploring new materials to serve as preconcentration media in micromachined heaters, including nanoscaled graphitic films, silsesquioxane derivatives, and metal-organic frameworks. Other collaborative engineering and materials development efforts are focused on microfabricated structures for particulate trapping, in-situ calibration, thermoelectric cooling, and tunable separations.
Dr. Zellers is a member of the executive committee of the NSF-funded Integrated Graduate Education and Research Training (IGERT) Program headquartered in the Chemistry Department a Task Leader in the NSF-funded Engineering Research Center on Wireless Integrated Microsystems headquartered in the Electrical Engineering and Computer Sciences Department; and Director of the Occupational Health and Industrial Hygiene Programs headquartered in the Department of Environmental Health Sciences.
K. Scholten, X. Fan, E. T. Zellers*, “A Microfabricated Opto-fluidic Ring Resonator Structure,” Appl. Phys. Lett. 99(14), 141108, 2011.
J. H. Seo, S. K. Kim, E. T. Zellers*, K. Kurabayashi*, “ Microfabricated Passive Vapor Preconcentrator/Injector Designed for Microscale Gas Chromatography,” Lab Chip, 12 (4), 717 – 724, 2012.
S. K. Kim, D. R. Burris, H. Chang, J. Bryant-Genevier, E. T. Zellers*, “Microfabricated Gas Chromatograph for On-Site Determinations of Trichloroethylene in Indoor Air Arising from Vapor Intrusion, Part I: Field Evaluation,” Environmental Science and Technology, 46, 6065-6072, 2012.
S. K. Kim, D. R. Burris, J. Bryant-Genevier, K. A. Gorder, E. M. Dettenmaier, E. T. Zellers*, “Microfabricated Gas Chromatograph for On-Site Determinations of TCE in Indoor Air Arising from Vapor Intrusion Part II: Spatial/Temporal Monitoring,” Environmental Science and Technology, 46, 6073-6080, 2012.
X. Mu, E. Covington, D. Rairigh, Ç. Kurdak, E.T. Zellers, A. J. Mason*, “A CMOS Monolithic Nanoparticle-Coated Chemiresistor Array for Microscale Gas Chromatography,” IEEE Sensors Journal, 12(7), 2444-2452, 2012.
G. Serrano, D. Paul, S.-J. Kim, K. Kurabayashi, E. T. Zellers*, “Comprehensive Two-Dimensional Gas Chromatographic Separations Using a Microfabricated Thermal Modulator,” Analytical Chemistry, 2012, 84 (16), pp 6973–6980.
G. Serrano, T. Sukaew, E. T. Zellers*, “Hybrid Preconcentrator/Focuser Module for Determinations of TNT Marker Compounds with a Micro-Scale Gas Chromatograph,” J. Chrom. A, 1279, 76-85, 2013.
K. Scholten, L. Wright, E. T. Zellers*, “Vapor Discrimination with Single- and Multi-Transducer Arrays of Monolayer-Protected-Nanoparticle Coated Chemiresistors and Resonators,” IEEE Sensors Journal, 13(6), 2146-2154, 2013.
T. Sukaew, E. T. Zellers*, "Evaluating the Dynamic Retention Capacities of Microfabricated Vapor Preconcentrators as a Function of Flow Rate,” Sensors and Actuators B Chemical, 183, 163-171, 2013.
K. Scholten, K. Reddy, X. Fan E. T. Zellers*, “Vapor Discrimination by Dual-Laser Reflectance Sensing of a Single Functionalized Nanoparticle Film,” Analytical Methods, 5(16), 4268-4272, 2013.
L. Wright and E. T. Zellers*, “Effects of flow rate and temperature on the performance of nanoparticle-coated chemiresistor arrays as micro-scale gas chromatograph detectors,” Analyst, 138(22), 6860-6868, 2013.
W. R. Collin, G. Serrano, L. K. Wright, H. Chang, N. Nuñovero, E. T. Zellers*, “Microfabricated Gas Chromatograph for Rapid, Trace-Level Determinations of Gas –Phase Explosive Marker Compounds,” Analytical Chemistry, 86, 655-663, 2014.