Ultra-Sensitive Microsensors for Chemical Analysis, pumpsandpipesmdhc


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Ultra-Sensitive Microsensors for Chemical Analysis, pumpsandpipesmdhc

  1. 1. Alan Schilowitz , Andy Riley, Dalia Yablon, Mark Disko ExxonMobil Research and Engineering Co. Corporate Strategic Research Laboratory Annandale, New Jersey Ultra-Sensitive Microsensors for Chemical Analysis
  2. 2. Why Microsensors ? <ul><li>High sensitivity </li></ul><ul><li>Low power consumption </li></ul><ul><ul><li>Enables wireless </li></ul></ul><ul><ul><li>Improved safety </li></ul></ul><ul><li>Redundancy </li></ul><ul><ul><li>Potential for large number of parallel sensors </li></ul></ul><ul><li>Portability </li></ul><ul><ul><li>Personal monitoring (e.g. badges) </li></ul></ul><ul><li>Small sample size </li></ul>
  3. 3. How Many Cantilevers Can Fit on the Head of a Pin ? 2 mm <ul><li>Two Modes of Operation </li></ul><ul><ul><li>Dynamic </li></ul></ul><ul><ul><li>Static </li></ul></ul>
  4. 4. Micro-Cantilevers Background <ul><li>Extension of Atomic Force Microscopy </li></ul><ul><ul><li>Some experiments carried out in Atomic Force Microscope head </li></ul></ul><ul><ul><li>Ultrahigh sensitivity to mass change </li></ul></ul><ul><li>Use for chemical measurement pioneered by Thundat (ORNL) and Gerber (IBM Zurich) </li></ul><ul><li>Applied to analysis of gas and aqueous solutions </li></ul><ul><li>Cantilevers commercially available in variety of shapes and materials </li></ul><ul><ul><li>Range of resonant frequencies, spring constants, shapes </li></ul></ul>Laser PSD Focusing Lens
  5. 5. <ul><li>Dynamic Mode </li></ul><ul><ul><li>Increasing viscosity changes resonance spectrum </li></ul></ul><ul><ul><li>Ultra sensitive to mass changes </li></ul></ul><ul><li>Cantilevers can be driven with piezo-electric crystal </li></ul><ul><li>Mass build-up changes resonant frequency </li></ul><ul><ul><li>Viscosity change alters resonant frequency and width of spectrum </li></ul></ul>Analysis in Dynamic Mode 0 2000 4000 6000 8000 10000 12000 Frequency (Hz) Amplitude Air Increasing Viscosity
  6. 6. Cantilevers Respond to Viscous Damping High Q Low Q Increasing Viscosity <ul><li>Viscosity can also be measured by frequency change </li></ul><ul><ul><li>Less sensitive than Q </li></ul></ul><ul><li>Measurements can be made on micro liter samples </li></ul>
  7. 7. Chemical Analysis in Static Mode <ul><li>Detection limit is in sub picogram range </li></ul>Selective adsorbant on one side only Untreated Cantilever Gold Coated Cantilever Detects Mercaptans Mercaptan Injection <ul><li>Static Mode - coated cantilevers respond to adsorption </li></ul><ul><ul><li>Detect deflection of cantilevers coated on one side </li></ul></ul>
  8. 8. Functionalized Cantilever Arrays for Aromatics Detection Self-Assembled Monolayers Impart Chemical Selectivity to Highly Sensitive Cantilever Transducers Self-Assembled Monolayer Candidates: SH Benzyl Mercaptan SH Naphthalenethiol SH OH Mercaptohexanol SH ( ) 6 Octadecanethiol
  9. 9. Cantilever Response To Aromatic Vapor <ul><li>Cantilevers exposed to aromatic vapor (parts per thousand) in laboratory air </li></ul><ul><li>Treated cantilevers have unique response to aromatics </li></ul>S OH S S ( ) 6 S toluene xylene toluene xylene d. ODT - octadecanethiol c. MH - mercaptohexanol b. NT - naphthalenethiol a. BM – benzyl mercaptan toluene xylene toluene xylene
  10. 10. Summary <ul><li>Micro-Cantilever sensor applications </li></ul><ul><ul><li>Viscosity on micro-liter samples </li></ul></ul><ul><ul><li>Potential for sub picogram chemical sensitivity </li></ul></ul><ul><li>Chemical specificity with Self Assembled Monolayers (SAM) </li></ul><ul><li>Potential for applications where: </li></ul><ul><ul><li>Sample size is limited </li></ul></ul><ul><ul><li>Large scale redundancy is desirable </li></ul></ul><ul><ul><li>Low power consumption is necessary </li></ul></ul>
  11. 11. Medical Applications Light traces are before exposure to e-coli Dark traces are after exposure B. Illic et.al., Appl. Phys. Lett. 77 (3), 450 (2000) E-Coli Sensor <ul><li>Vibrational frequency reduced as cells bind to cantilever </li></ul><ul><ul><li>Frequency = </li></ul></ul>W. Guanghua et.al., Nature Biotechnology 19 , 856 (2001) Prostate Specific Antigen (PSA) Sensor
  12. 12. References - Medical Applications Rapid and label-free nanomechanical detection of biomarker transcripts in human RNA Zhang, J.; Lang, HP.; Huber, F.; Bietsch, A.; Grange, W.; Certa, U.; McKendry, R . ; Guntherodt, HJ.; Hegner, M. & Gerber, Ch.  Nature Nanotechnology , 1 , 214-220 (2006). Novel electrical detection of label-free disease marker proteins using piezoresistive self-sensing micro-cantilevers Wee KW, Kang GY, Park J, Kang JY, Yoon DS, Park JH, Kim TS Biosens Bioelectron 2005 Apr 15;20(10):1932-8 Array of Nano­Cantilevers as a Bio­Assay for Cancer Diagnosis Klein, K.M.; Jiantao Zheng; Gewirtz, A.; Sarma, D.S.; Rajalakshmi, S.; Sitaraman, K. Electronic Components and Technology Conference, 2005. Proceedings. 55th Volume , Issue , 31 May-3 June 2005 Page(s): 583 - 587 A Review of Microcantilevers for Sensing Applications Vashist, S.K., June 2007 www.azonano.com/details.asp?ArticleID=1927