Organically modified silicate film pH sensor for continuous wound monitoring

In this contribution we present a miniaturized optical reflectance pH sensor based on organically modified silicate for continuous measurements of wound pH. Colorimetric indicators (bromocresol green pH 3.8-5.4 and bromocresol purple pH 5.2-6.8) have been immobilized in tetraethoxysilane (TEOS) thin films. Characteristics of the thin films have been optimized by addition of (3-Glycidyloxypropyl)trimethoxysilane (GLYMO). The pH sensitive layer of the sensor is illuminated through the substrate by a chip-LED. The reflected light at a phototransistor varies in dependence of the color of the thin film. The films have been characterized by visible absorption spectroscopy and the performance of the sensor has been evaluated by measurements on artificial wounds.