2004 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, 2003 through December 31, 2004
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 2 of the project were to: (1) examine in situ, direct detection of various water-borne pathogens including Escherichia coli 0157:H7 and Salmonella typhimurium using PZT cantilevers with antibodies immobilized on various surfaces such as gold and titanium and (2) 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 the area of detection, PZT/Au-coated glass and PZT/Ti cantilevers were constructed for Salmonella detection. These cantilevers were 2 mm wide and less than 1 mm long with a 2mm- long Au-coated glass or Ti tip of 2 mm. The Au-coated surface was coated with mercaptoproprionic acid (MPA) and activated by 1-Ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC), sulfo- N-Hydroxysuccinimide (sulfo-NHS). The Ti surface was activated by nitric acid and coated with Glycidoxypropyl trimethoxysilane (GOPTS) for antibody immobilization. Both immobilization methods showed comparable Salmonella binding efficiency. In this period, we also achieved detection using two cantilevers with one coated with an irrelevant antibody as the reference that measured the frequency shift resulting from the background. This is a major step forward. It allowed instantaneous accurate background subtraction. With the PZT/Au-coated cantilevers, we showed that the sensor was capable of detecting S. typhimurium at 1,000 cells/mL concentrations, which was well below the infection dosage, 105 cells/mL, and the current ELISA sensitivity, 105 cells/mL.
In the PMN-PT film processing and PMN-PT microcantilever array fabrication, we have achieved as thin as 20μm PMN-PT freestanding film by tape casting and sintering at 1,000 °C, 200 °C lower than the typical PMN-PT sintering temperature. The obtained PMN-PT freestanding film exhibited a giant electric-field enhanced piezoelectric coefficient, d 31, of 2000 pC/m, higher than those of specially-cut single crystals and more than seven times higher than that of typical bulk polycrystalline PMN-PT. The extraordinary piezoelectric performance of the freestanding PMN-PT film was attributed to: (1) the substrate-free low-temperature sintering, and (2) the thin film geometry. The former helped maintain the stoichiometry, crucial for piezoelectric performance, and the latter allowed better electric field penetration for domain orientation, key for high piezoelectric performance. The PMN-PT/Cu microcantilever arrays were obtained by first electroplating 5-μm thick Cu as the nonpiezoelectric layer followed by wire-saw cutting. A 500μm long PMN-PT/Cu microcantilever exhibited better than 10-13 g/Hz detection sensitivity. A wire bonder donated by Kulicke & Soffa will help realize electrical connection to the miniaturized cantilever. Electrical insulation also was underway to encapsulate the sensor for total submersion in water.
We will fabricate insulated PMN-PT/Cu microcantilever arrays 100 m m long for simultaneous, in situ, detection of multiple pathogens with femtogram sensitivity.
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|
||Luo H, Shih WY, Shih WH. Comparison in the coating of Mg(OH)2 on micron-sized and nanometer-sized Nb2O5 particles. International Journal of Applied Ceramic Technology 2004;1(2):146-154.||