Convergent, self-encoded bead sensor arrays in the design of an artificialnose

We report a new approach to designing an artificial nose based on high-dens ity optical arrays that directly incorporate a number of structural and ope rational features of the olfactory system. The arrays are comprised of thou sands of microsphere (bead) sensors, each belonging to a discrete class, ra ndomly dispersed across the face of an etched optical imaging fiber. Beads are recognized and classified after array assembly by their unique, "self-e ncoded" response pattern to a selected vapor pulse, The high degree of redu ndancy built into the array parallels that found in nature and affords new opportunities for chemical-sensor signal amplification. Since each bead is independently addressable through its own light channel, it is possible to combine responses from same-type beads randomly distributed throughout the array in a manner reminiscent of the sensory-neuron convergence observed in the mammalian olfactory sq-stem, Signal-to-noise improvements of approxima tely n(1/2) have been achieved using this method.