2003 Progress Report: Ultrasensitive Pathogen Quantification in Drinking Water Using Highly Piezoelectric PMN-PT MicrocantileversEPA Grant Number: R829604
Title: Ultrasensitive Pathogen Quantification in Drinking Water Using Highly Piezoelectric PMN-PT Microcantilevers
Investigators: Shih, Wan Y. , Mutharasan, R. , Shih, W.-H.
Institution: Drexel University
EPA Project Officer: Lasat, Mitch
Project Period: January 1, 2002 through December 31, 2004 (Extended to December 31, 2005)
Project Period Covered by this Report: January 1, 2002 through December 31, 2003
Project Amount: $449,713
RFA: Exploratory Research: Nanotechnology (2001) RFA Text | Recipients Lists
Research Category: Safer Chemicals , Nanotechnology
The ultimate objective of the research project is to develop highly piezoelectric microcantilever arrays for in situ, rapid, simultaneous multiple pathogen quantification in source water with the ability to detect pathogens using electrical means with unprecedented sensitivity (10-15 g). The piezoelectric microcantilevers with antibodies specific to the target pathogens immobilized at the cantilever tip will measure the presence of pathogens with femtogram (a small fraction of a cell’s mass) sensitivity in source water. This represents the ability to detect a single cell. This project is both a beneficiary and an enabling technology involving nanometer scale engineering. The fabrication of the extremely highly piezoelectric, but difficult to make, lead magnesium niobate-lead titanate (PMN-PT) solid solution thin layers involves coating Mg(OH)2 nanolayers on nanometer-size niobium oxide particles. The proposed sensor offers the unprecedented ability to detect and manipulate a nanometer-size object— a single pathogen in water.
The short-term goals for Year 1 of the project were to: (1) examine the in-situ detection detail using millimeter size cantilevers made with commercial lead zirconate titanate (PZT), and (2) develop a low-sintering-temperature processing method for PMN-PT films with optimized piezoelectric properties for PMN-PT microcantilever fabrication.
In the area of detection, PZT/glass cantilevers 2 mm wide and less than 1 mm long with a glass tip of 2 mm in length were successfully constructed using 127μm thick PZT and 150μm thick glass layers. Antibodies specific to Escherichiacoli 0157:H7 were immobilized on the glass tip. Two antibody immobilization methods have been investigated: The first involved activation of the antibody with 1-Ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC), sulfo- N-Hydroxysuccinimide (sulfo-NHS), and the second involved activation of the carbohydrate groups attached to the CH2 domain in Fc region of the antibody to result in site-directed coupling. The antibody immobilized PZT/glass cantilevers were used to detect E. coli 0157:H7 in the concentration range 7 x 102 to 7 x 107 cells/mL and also in mixtures of E. coli 0157:H7 with it nonpathogenic variant. The results indicated that the current PZT/glass cantilevers were capable of selectively detecting E. coli 0157:H7 in concentrations above 1,000 cells/mL.
In the PMN-PT film processing, lead loss above 1,000 °C and the presence of a pyrochlore phase were the two main challenges of the PMN-PT film processing. Both lead loss and the presence of the pyrochlore phase can severely degrade the piezoelectric performance of the film. To circumvent lead loss and the presence of the pyrochlore phase, a novel nanocoating approach was developed to achieve an unprecedented low sintering temperature, 1,000 °C, 200 °C lower than the typical PMN-PT sintering temperature, by a reaction sintering mechanism. The highly reactive PMN-PT powder derived from PT precursor-coated PMN powders ensured that the final PMN-PT is single phase and the low-temperature sintering eliminated the lead loss. The resulted PMN-PT ceramics exhibited a high dielectric constant of 2000, a saturation polarization of about 30 μC/cm2, and a remnant polarization of 25 μC/cm2. This low-temperature sinterable PMN-PT powder is ready for film processing and microcantilever fabrication.
In the area of detection, we will continue to examine in-situ, direct detection of water-borne pathogens including E. coli 0157:H7 and Salmonella using PZT/glass cantilevers. We also will examine methods to immobilize antibodies on other surfaces such as gold and titanium. Detection using more than one cantilever also will be carried out. In the area of PMN-PT microcantilever fabrication, we will use the highly reactive PMN-PT precursor powder we have developed to fabricate PMN-PT freestanding films by tape casting and use the freestanding PMN-PT films to fabricate microcantilever arrays for simultaneous, in-situ, detection of multiple pathogens in water.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
|Other project views:||All 33 publications||12 publications in selected types||All 7 journal articles|
||Yi JW, Shih WY, Mutharasan R, Shih WH. In situ cell detection using piezoelectric lead zirconate titanate-stainless steel cantilevers. Journal of Applied Physics 2003;93(1):619-625.||