Evaluating the chemical spatial resolution of imaging fiber chemical sensors

The combined imaging and chemical sensing (CICS) technique permits the conc urrent viewing of a remote sample's morphology and interfacial chemistry. I t utilizes charge coupled device-based epifluorescence microscopy and imagi ng fiber chemical sensors (IFCSs). Traditionally, IFCSs have been fabricate d by spin-coating a planar chemical sensing layer (polymer + indicator) acr oss the distal polished imaging fiber face. The parameters affecting an ima ging fiber's optical spatial resolution have been well documented. In this work, an IFCS's chemical spatial resolution was evaluated using fluorescent dye embedded microbeads. Beads were deposited atop polished imaging fiber faces and were recessed inside individual microwells that were etched acros s an imaging fiber's face. Negligible fluorescence from bead-containing mic rowells was captured by microwells neighboring bead-containing microwells. Conversely, significant fluorescence from beads atop polished imaging fiber s was captured by neighboring cores. The background-subtracted contrast/noi se ratio for a bead-containing microwell array was 800:1 and that for a bea d-covered imaging fiber was 16:1. This is the first quantitative report of such observations and recommendations are made for future IFCS utilization with the CICS technique. (C) 2001 Elsevier Science B.V. All rights reserved .