A far-field-viewing sensor for making analytical measurements in remote locations

We demonstrate a far- field-viewing GRINscope sensor for making analytical measurements in remote locations. The GRINscope was fabricated by permanent ly affixing a micro-Gradient index (GRIN) lens on the distal face of a 350- mu m-diameter optical imaging fiber. The GRINscope can obtain both chemical and visual information. In one application, a thin, pa-sensitive polymer l ayer was immobilized on the distal end of the GRINscope. The ability of the GRINscope to visually image its far-field surroundings and concurrently de tect pH changes in a flowing stream was demonstrated. In a different applic ation, the GRINscope was used to image pH- and O-2-sensitive particles on a remote substrate and simultaneously measure their fluorescence intensity i n response to pH or pO(2) changes.