Proc. SPIE-Int. Soc. Opt. Eng. 2000, 4177 (Microfluidic Devices and Systems III), 212-219.

Liquid Flow Through an Array-Based Chemical Sensing System

Y.-S. Sohn, A. Tsao, E. V. Anslyn, J. T. McDevitt, J. B. Shear

A micromachined fluidic sensor array for the rapid characterization of multiple analytes in solution has been developed. A simple micromachined fluidic structure for this biological and chemical agent detection system has been designed and fabricated, and the system has been tested. Sensing occurs via optical changes to indicator molecules that are attached to polymeric microspheres (beads). A separate charged-coupled-device (CCD) is used for the simultaneous acquisition of the optical data from the selectively arranged beads in micromachined etch cavities. The micromachined bead support structure has been designed to be compatible with this hybrid optical detection system. The structure consists of four layers: cover glass, micromachined silicon, dry film photoresist, and glass substrate. The bottom three layers are fabricated first, and the beads are selectively placed into micromachined etch cavities. Finally, the cover glass is applied to confine the beads. This structure utilizes a hydrophilic surface of the cover glass to draw a liquid sample into the sensor array without moving components, producing a compact, reliable, and potentially low-cost device. We have initially characterized fluid flow through a complete chip, showing complete filling of the sample chamber in approximately 2 seconds. The test results show that this system may be useful in micro total analysis systems (µ - TAS), especially in single-use biomedical applications.