Evaluating the chemical spatial resolution of imaging fiber chemical sensors

The combined imaging and chemical sensing (CICS) technique permits the concurrent viewing of a remote sample's morphology and interfacial chemistry. It utilizes charge coupled device-based epifluorescence microscopy and imaging fiber chemical sensors (IFCSs). Traditionally, IFCSs have been fabricated by spin-coating a planar chemical sensing layer (polymer + indicator) across the distal polished imaging fiber face. The parameters affecting an imaging 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 across an imaging fiber's face. Negligible fluorescence from bead-containing microwells was captured by microwells neighboring bead-containing microwells. Conversely, significant fluorescence from beads atop polished imaging fibers was captured by neighboring cores. The background-subtracted contrast/noise ratio for a bead-containing microwell array was 800:1 and that for a bead-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.