INTEGRATED OPTICAL PH SENSOR USING REPLICATED CHIRPED GRATING COUPLERSENSOR CHIPS

Integrated optical sensor chips suitable for high-resolution pH measur ements are presented. The pi-I-sensitive swelling of a polymer membran e is detected by refractometry using a compact multi-channel sensor mo dule. The signal transduction is achieved by means of chirped grating couplers which allow simple yet high functionality sensor modules to b e built. The experiments have been performed with high sensitivity rep licated polycarbonate TiO2 waveguide sensor chips coated with an ultra thin photopatterned hydrogel membrane having functional groups which r eversibly change from the neutral state to a charged state upon acidif ication. A resolution delta pH < + 1.1 x 10(-4) in terms of the pH (at pH 7.5) has been obtained in a dual-channel module with size 10 x 10 x 10 cm(3). (C) 1998 Elsevier Science S.A. All rights reserved.