Micromachined Chemical Sensors: Towards an Electronic Tongue

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In collaboration with Eric Anslyn, John McDevitt, and Jason Shear, we are working on new chemical sensors. Shown below is a Quicktime movie of a polystyrene bead that has been "tagged" so that there is a very strong (and reversible) optical color change when the pH of the bead's environement changes. We are studying micromachined "micro-test tubes" and integrated optical interfaces to allow the compact packaging of arrays of such sensing beads.

• Executive summary of the potential capabilities of our "electronic tongue" (pdf file)

Click on the image above to see a color movie of beads while solutions of changing pH are introduced (quick time, 625k).

Click on the image above to see a nicer color movie of an array, again responding to pH changes, but over a ten decade range in concentration (Real Video, streaming, 200k total). These movies were done by co-workers in John McDevitt's lab.

Click on the image above to see a Real Video stream of a bead placement operation (~300k total); placement and movie done by Youngsoo Sohn and Rob Friar.

Development of a Multi-analyte Sensor Array Composed of Receptor-tagged Polymeric Microspheres Localized in Micromachined Cavities

to be submitted Chemistry of Materials (3/12/98)

Steve Savoy, John J. Lavigne, Jascinda Clevenger, J. Seung-Jin Yoo,

John T. McDevitt, Eric V. Anslyn, Jason B. Shear, Dean Neikirk

Contribution from Department of Chemistry and Biochemistry

Department of Electrical Engineering

The University of Texas at Austin

Austin, TX 78712

Abstract:

The development of a sensor array composed of individually immobilized polystyrene-polyethylene glycol composite microspheres has been demonstrated. The microspheres are selectively arranged in micromachined etch cavities localized on silicon wafers which have the rear face terminated with a Si3N4-SiO2-Si3N4 transparent membrane structure. The membrane acts as a window and enables studies of the optical properties of the sensing elements upon their exposure to analyte-carrying aqueous solutions. Sensing occurs via colorimetric or fluorometric changes to receptor molecules which are covalently bound to amine termination sites on the polymeric microspheres. The unique combination of carefully chosen reporter molecules with water permeable microspheres allows for the simultaneous detection and quantification of a variety of analytes. The fabrication of the sensor structure and the initial colorimetric and fluorescent responses using a charge-coupled device (CCD) detector for pH, Ca+2, Ce+3, and sugar are reported. In addition, response time for selected microsphere structures is described.

Also see:

• J. J. Lavigne, S. Savoy, M. B. Clevenger, J. E. Ritchie, B. McDoniel, S.-J. Yoo, E. V. Anslyn, o. T. McDevitt, J. B. Shear, and D. Neikirk, "Solution-Based Analysis of Multiple Analytes by a Sensor Array: Toward the Development of an "Electronic Tongue," JACS, vol. 120, July 1, 1998, pp. 6429-6430.
• S. Savoy, J. J. Lavigne, J. S.-J. Yoo, J. Wright, M. Rodriguez, A. Goodey, B. McDoniel, J. T. McDevitt, E. V. Anslyn, J. B. Shear, A. Ellington, and D. P. Neikirk, "Solution-based analysis of multiple analytes by a sensor array: toward the development of an electronic tongue," SPIE Conference on Chemical Microsensors and Applications, SPIE Vol. 3539, Boston, MA, Nov. 4, 1998.
  • slides used in conjunction with our talk the SPIE Conference on Chemical Microsensors and Applications, SPIE Vol. 3539, Boston, MA, Nov. 4, 1998.
• Youngsoo Sohn, John Levigne, Dr. Yi Deng, Adrian Goodey, Marc Rodriquez, Andrew Tsao, Theodore E. Curey, Dean P. Neikirk, Eric Anslyn, John McDevitt, and Jason Shear, ìMicromachined multi-analyte sensors: towards an ëelectronic tongueí,î NASA NanoSpace 2000, International Conference on Integrated Nano/Microtechnology for Space Applications, League City, TX, Jan. 23-28, 2000.
  • slides used during our talk:
  • pdf file ( 818K)
  • animated powerpoint presentation complete with movies (you'll probably need to use MS Internet Explorer and a pc to view this; the movies are also big, so you need a fast internet connection...)
• References for other work on chemical sensors.
• Press stories on the "e-tongue".

For other information on some of our chemical sensor work, please see our paper:

J. Han, D. P. Neikirk, M. Clevenger, and J. T. McDevitt, "Fabrication and characterization of a Fabry-Perot based chemical sensor," SPIE Microelectronic Structures and MEMS for Optical Processing II, M. E. Motamedi and W. Bailey, editors, Proc. SPIE 2881, Austin, Texas, USA, 14-15 October, 1996, pp. 171-178.

Slide show on micromachined storage wells for an"electronic tongue" .

Return to research overview in the Microelectromagnetic Device Group