Optical Chemical Sensor Systems based on Photosensitive Hybrid Sol-Gel Glass B.D. MacCraith, S. Aubonnet, H. Barry, C. von Bültzingslöwen, J.-M. Sabattié, C.S. Burke Optical Sensors Laboratory - National Centre for Sensor Research Dublin City University - Ireland Tailoring the microstructure Basic Recipe MAPTMS / Zirconium propoxide TEOS / methacrylic acid Ru tris diphenyl phenanthroline water acid / base catalyst (cf. table) Stern-Volmer plots 4 Doped Materials: Oxygen Sensing The luminescence of ruthenium poly-pyridyl complexes is quenched reversibly by oxygen (Dynamic Quenching) Such complexes (e.g. Ru tris diphenyl phenanthroline) can be excited by blue LEDs and emit in red Quenching process described by Stern-Volmer equation I 0 / I = 1 + K SV [ O 2 ] where I 0 is the unquenched luminescence intensity The Stern-Volmer constant K sv is a direct measure of sensitivity K SV  D, the diffusion coefficient of O 2 in the matrix 2 Objectives To demonstrate the capability of doped photo-patternable sol-gel glass for sensor applications. To investigate the tunability of such sensor systems To exploit the photolithographic properties of these materials to prepare a range of sensor configurations. To demonstrate the usefulness of this system for micro-total-analysis (Lab-on-a-chip) devices. 1 Introduction Much interest in hybrid organic-inorganic sol-gel glasses that can be photo-patterned by UV irradiation. Principal application is the fabrication of integrated optic devices for telecommunication applications, e.g. splitters, DWDM’s. These materials have considerable potential for chemical sensing systems, including optodes (doped materials) and micro-total-analysis (Lab-on-a-chip) devices. 5 Sensor Configurations Photosensitive sol-gel glass can be used to produce a range of useful sensing configurations, e.g. integrated optic structures and arrays of sensor spots The fluorescence is captured in each waveguide and can be observed at the channel output. Average ridge thickness of 14.5  m 200  m Photopatterned array of doped sensor spots Detector Array Sensor Spot Waveguide Blue LED 6 Microsystems (Lab-on-a-chip) Major developments in miniaturised sensor systems with high levels of integration and functionality, e.g.  -TAS (micro-total-analysis systems) Key  -TAS elements include microfluidic channels and patterned surfaces UV-photolithographic sol-gel materials can be used for rapid prototyping, templating of PDMS (poly-dimethyl siloxane), and patterning of surfaces. UV-cured sol-gel ridges (50  m width) Silicon substrate PDMS micro channels PDMS drop 7 Conclusions UV-curable sol-gel materials combine the versatility of the sol-gel process with the capabilities of photolithography. Tunable doped sensor materials, waveguide sensor structures and sensor arrays can be fabricated with this process. Future work: micro-optical sensor chips and multi- analyte sensor systems 3 Photosensitive Sol-Gel Preparation Principles: Presence of UV curable moiety (MAPTMS - methacryloxypropyl-trimethoxysilane) enables spatially selective curing of sol-gel matrix. The Photoinitiator splits into radicals upon UV illumination (Step 1). The photoinitiator radicals react with the unsaturated groups of MAPTMS (Step 2). The reaction propagates by radical addition to unsaturated groups of MAPTMS (Step 3). The non-polymerised MAPTMS is washed away using Isopropanol UV Step 1 Step 2 Step 3 Photoinitiator MAPTMS Mask IPA wash Substrate Photosensitive layer Substrate UV light Photopatterning