Edward T. Zellers, PhD
- Professor Emeritus, Environmental Health Sciences
- Professor, Chemistry
Professor Zellers' research and teaching programs are concerned with various aspects of characterizing and controlling human exposures to toxic chemicals, including sampling and analytical methods and instrumentation, assessment strategies, and protective equipment. His primary research interests are in the development of microfabricated sensor arrays and integrated microanalytical systems for the direct determination of organic compounds in air and biological media and for characterizing the interfacial interactions of such compounds with various media. Among the applications being pursued for these new chemical sensing technologies are miniaturized, wireless instrumentation for indoor-air quality assessments, personal-exposure monitoring, breath analysis, ambient air pollution mapping, and in-situ assessments of the barrier effectiveness of polymeric chemical protective clothing. Prof. Zellers maintains an active interdisciplinary research group that involves collaborations among students, faculty, and research scientists from several UM departments, national laboratories, and small RandD firms. He teaches lecture and laboratory courses on chemical hazard evaluation, exposure assessment, and chemical microsensors and microsystems. As director of the Occupational Health Program, Dr. Zellers administers the industrial hygiene component of the NIOSH-funded Education and Research Center Training Grant. He is a member of the faculty in the Department of Chemistry and serves as a Group Leader in the NSF-funded Engineering Research Center for Wireless Integrated MicroSystems (WIMS) headquartered in the Department of Electrical Engineering and Computer Science.
- PhD, Environmental Health Sciences, University of California, Berkeley, 1987
- MS, Environmental Health Sciences, University of California, Berkeley, 1984
- BA, Chemistry, Rutgers University, 1978
The assessment of human exposures to toxic chemicals and the implementation of effective control measures rank among the most important components of occupational and environmental health practice. Our ability to meet evolving needs in these areas relies critically on technological and methodological innovation and on a thorough understanding of the relevant underlying chemical interactions governing the operation and performance of monitoring and control technologies. Dr. Zellers' interests in occupational and environmental health relate to both the fundamental and applied aspects of chemical hazard evaluation and control. His current research interests are in 1) the development of chemical sensors and sensor arrays for monitoring simple organic molecules in air and biological media, and for characterizing thin films, 2) the implementation of sensor-based systems for occupational and environmental monitoring applications, 3) the development of integrated microanalytical systems for multi-vapor analysis, and 4) the characterization and modeling of polymer-solvent interactions as they affect the barrier properties of the polymer to solvent permeation. This research is highly interdisciplinary, involving collaborations with faculty and students from several other departments on campus, as well as researchers at national laboratories and private research and development firms. Dr. Zellers' research group has included graduate and undergraduate students majoring in chemistry, occupational and environmental health science, materials science, and chemical, electrical, and biomedical engineering. Through formal classwork, an intensive research experience, regular group meetings, seminars, and presentations students receive training in a diverse range of applied science and engineering concepts and cutting-edge technologies relevant to chemical exposure assessment and control. An emphasis is placed on developing students problem solving skills and technical expertise in preparation for careers in research and development. 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 (WIMS) 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. In the area of chemical sensors, Dr. Zellers' group has focused primarily on microsensors that utilize surface-acoustic-wave (SAW) propagation through small piezoelectric substrates. Investigations have involved the synthesis of novel chemically selective interface (coating) materials, elucidation of the mechanisms by which the coatings 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/testing of practical sensor-based instrumentation. Integration of these sensors with other micromachined components to create miniaturized analytical systems employing novel valve, pump, preconcentrator, and sensor-array designs is also being actively explored. Among the sensor interface materials examined are Pt-olefin p complexes of the general formula trans-PtCl2(amine)(olefin), which react via substitution of the initially bound olefin with specific gas-phase olefins or dienes. Post-exposure regeneration of the initial complex in-situ extends the service life of the sensor. Functionalized polymers can also serve as effective SAW sensor coatings for vapor-phase analytes. In this case, an array of sensors is used and the pattern of responses is correlated with the identity of the analyte. Sensor responses are based on partitioning phenomena, which can be modeled accurately using approaches originally applied to gas chromatography. Chemometric and Monte Carlo analyses can be used to optimize the design and performance of the array. The development of new polymeric coatings, such as those employing side-chain liquid crystalline polymers which differentiate vapors on the basis of size and shape, is currently being pursued. In addition, the use of other sensor technologies, such as chemiresistors, which respond to changes in the electronic properties of the interface material, are being developed for use in multisensor arrays to increase the amount of information extractable from the array for vapor identification. Toward this end, monolayer encapsulated metal nanoclusters (MenMs) are being developed and tested. These interesting materials present a wide range of possibilities for chemical selectivity and can be fashioned into networks of nano-scale capacitors or connected via conducting moieties to create chemically sensitive molecular wiring systems. Deposition and patterning via scanning probe microscopy is also possible and will allow construction of ultra-miniature sensor arrays. Increasing evidence suggests that the number of vapors that can be simultaneously recognized and differentiated with standalone sensor arrays is limited and that quantitative analyses of even moderately complex vapor mixtures will require coupling the microsensor array to an upstream gas-chromatographic separation stage. For detecting low analyte concentrations, preconcentration may also be required, particularly for applications in indoor air-quality (IAQ) monitoring and ambient environmental monitoring where vapor concentrations are typically in the low- or sub-part-per-billion range. Coupling sensor arrays to preconcentration and chromatographic stages to create microanalytical systems capable of analyzing complex vapor mixtures of arbitrary composition is currently being explored. Functional integration of preconcentration, separation, and sensor-array detection stages will allow a synergy of capabilities that will enhance overall microsystem performance. The ultimate goal of this work is to use Si micromachined, or so-called MEMS technology (MEMS: microelectromechanical systems) to create ultra-low power, wireless 'lab-on-a-chip' systems. For preconcentration, various adsorbent materials are being developed, including carbon molecular sieves, graphitized carbons, and porous polymers. In addition, we are synthesizing organic/inorganic hybrid nanocomposite materials consisting of derivatized silsesquioxanes with tailored surface areas, pore-size distributions, and functionalities for use in multi-stage preconcentator structures. Efforts to combine these adsorbents with novel, low-power, micromachined heater structures for thermal desorption are also underway. For separation of complex mixture components, we are assisting in the development of chromatographic separation channels from etched silicon wafers. Among the many challenges to creating such small systems is depositing a thing uniform stationary phase on the walls of high-aspect-ration vertically etched channels. Toward this end we have explored UV-photopolymerization of gas-phase monomers. Other approaches are also being pursued. Models of solvent permeation through polymer barriers have been developed in our group to predict the protection provided by gloves and encapsulating suits worn in hazardous environments. These models employ solubility parameters, solvation parameters in conjunction with linear solvation energy relationships, and other semi-empirical approaches to correlate the physicochemical properties of the solvents and polymer barrier materials with the permeation behavior. Complementing this work, we have critically examined current standardized testing methodologies and have developed microsensor-based instrumentation for field analysis of the permeation resistance of protective clothing materials. Applications in occupational and environmental health, as well as civilian counter-terrorism are being considered.
Microanalytical System for Indoor Volatile Organic Compounds (VOC) Monitoring
Wireless Integrated Microsystems National Science Foundation Engineering Research
Rapid Determination of Airborne ETS Markers with a Novel Field Instrument
Sponsor: University of Michigan Tobacco Research Network
Analysis of Vapor-Phase Currency Marker Compounds
Sponsor: Idaho National Engineering and Environmental Laboratory
The University of Michigan Education and Research Training Center - Industrial Hygiene
Wang, J. N. Nunovero, R. Nidetz, S. Peterson, B. Brookover, W. H. Steinecker, and E. T. Zellers (2019). "Belt-Mounted Micro Gas Chromatograph Prototype for Determining Personal Exposures to VOC Mixture Components," Analytical Chemistry, 91, 4747-4754 (http://dx.doi.org/10.1021/acs.analchem.9b00263)
Wang, J., J. Ma, and E.T. Zellers (2019). Room-Temperature-Ionic-Liquid Coated Graphitized Carbons for Selective Preconcentration of Polar Vapors, J. Chrom. A, web publication, Aug. 31, 2019.
Lin, Z. N. Nunovero, J. Wang, R. Nidetz, S. Buggaveeti, K. Kurabayashi, and E. T. Zellers (2018). A Zone-Heated Gas Chromatographic Microcolumn: Energy Efficiency, Sensors and Actuators B: Chemical, 254: 561-572.
Wang, J., J. Bryant-Genevier, N Nunovero, C. Zhang, B. Kraay, C. Zhan, K. Scholten, R. Nidetz, S. Buggaveeti and E. T. Zellers (2018). Compact Prototype Microfabricated Gas Chromatographic Analyzer for VOC Mixtures at Typical Workplace Concentrations, Microsystems and Nanoengineering, 4, 1710.
Collin, W.R., N. Nunovero, D. Paul, K. Kurabayashi and E.T. Zellers (2016). Comprehensive Two-Dimensional Gas Chromatographic Separations with a Temperature Programmed Microfabricated Thermal Modulator, J. Chrom., A, 1444, 114-122.
Collin, W.R., K.W. Scholten, X. Fan, D. Paul, K. Kurabayashi and E.T. Zellers (2016). Polymer-Coated Micro-Optofluidic Ring Resonator Detector for a Comprehensive Two-Dimensional Gas Chromatographic Microsystem: mGC x mGC- mOFRR, Analyst, 141, 261-269.
Collin, W., A. Bondy, D. Paul, K. Kurabayashi and E.T. Zellers (2015). Comprehensive Two-Dimensional Gas Chromatographic Separations with Microfabricated Components, Analytical Chemistry, 87 (3), 1630-1637.
Bryant-Genevier, J. and E.T. Zellers (2015). "Toward a Microfabricated Preconcentrator Focuser for a Wearable Microscale Gas Chromatograph," J. Chrom. A, 1422, 299-309, DOI: 10.1016/j.chroma.2015.10.045.
Scholten, K.w., W.R. Collin, X. fan and E.T. Zellers (2015). "Nanoparticle-Coated Micro-Optofluidic Ring Resonator as a Detector for Microscale Gas Chromatographic Vapor Analysis" Nanoscale, 7, 9282-9289, PMID:25939851.
Bryant-Genevier, J., S.K. Kim, K. Scholten and E.T. Zellers. (2014). "Multivariate Curve Resolution of Partially Resolved Analytes Measured by Gas Chromatography with Microsensor Array Detection," Sensors and Actuators B Chemical, 202, 167-176.
Scholten, K., X. Fan, E.T. Zellers (2014). A Microfabricated Optofluidic Ring Resonator for Sensitive, High-Speed Detection of Volatile Organic Compounds, Lab Chip, 14 (19), 3873-3880.
Collin, W.R., G. Serrano, L.K. Wright, H. Chang, N. Nunovero and E.T. Zellers (2014). Microfabricated Gas Chromatography for Rapid, Trace-Level Determinations of Gas-Phase Explosive Marker Compounds. Analytical Chemistry,655-663.
Wright, L. and E.T. Zellers (2013). Effects of Flow-rate and Temperature on the Performance of Nanoparticle-coated Chemiresistor Arrays as Micro-scale Gas Chromatograph Detectors. Analyst 6860-6868.
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