S. -J. Yoo, J. Lavigne, S. Savoy, J. B. McDoniel, E. V. Anslyn, J. T. McDevitt, D. P. Neikirk, J. B. Shear, "Micromachined storage wells for chemical sensing beads in an 'artificial tongue'," SPIE's Micromachining and Microfabrication '97 Symposium: Micromachined Devices and Components III, K. Chau and P. J. French, editors, Proc. SPIE 3224, Austin, Texas, USA, 29-30 September, 1997.
S. -J. Yoo, J. Lavigne, S. Savoy, J. B. McDoniel, E. V. Anslyn, J. T. McDevitt, D. P. Neikirk, J. B. Shear
Department of Chemistry and Biochemistry and Department of Electrical and Computer Engineering
The development of smart sensors capable of discrimination of different analytes, toxins, and bacteria has become increasingly important for real time diagnosis of pathogens. In particular, molecules that change their optical properties when exposed to the target material provide the potential for highly sensitive detection. A very powerful tool for the synthesis of these compounds involves the use of polymer bead substrates. The size and shape of these beads (typically spheres of radius a few tens to hundreds of micrometers in diameter) as well as the fact that they may actually change size (e.g., swell or shrink) when their chemical environment changes presents a significant challenge in the assembly of complete sensing platforms. Here we will discuss new micromachined arrays that both localize and allow optical access to new chemical sensing beads. A typical process involves a conventional bulk micromachining step used to form pyramidal pits in a silicon substrate, sized to allow a sensing bead to rest inside it, and a transparent cover plate placed on top to keep the bead in place. Illumination can then be applied to one side, while a photodetector is placed on the other. The spacing between the cover and the silicon substrate is smaller than the diameter of the bead so that the bead cannot escape, but fluid can be exchanged. For optical detection, the micromachined bead array can be placed directly over a commercially available CCD array. This hybrid assembly is relatively simple, while allowing separate optimization of the analyte sensing and photodetection sections of the system. Interface to microfluidic components is also possible, producing a complete sampling/sensing system.
also see "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.