Adaptive coatings in micro-capillaries and micro-channels as new means to develop integrated micro-fluidic optical sensors.
Florea , Larisa and Diamond, Dermot and Benito-Lopez, Fernando (2011) Adaptive coatings in micro-capillaries and micro-channels as new means to develop integrated micro-fluidic optical sensors. In: Seminar in Micro-fluidics, UC Berkeley, 10th Oct 2011, Berkeley, CA..
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Optical chemical sensors usually employ a dye or indicator that should be immobilised onto a solid support material. This type of optical chemical sensors present two main problems: firstly, the dye should retain its optical properties after the immobilisation process and secondly, it should not leach to the solution. Therefore, the development of such sensors has focused on the search for new materials, which overcome these problems. One alternative has been the development of chemical sensors based on adaptive polymeric materials. If these materials display optical properties in the visible region that change in response to a target chemical specie then they can be easily used as optical sensors.
Our approach is to coat the inner walls of micro-channels and micro-capillaries with adaptive polymeric materials that can be employed as optical sensing platforms for a variety of target species. Two types of adaptive coatings will be discussed here. The first one is based on the conductive polymer polyaniline (PAni). Using the “grafting” approach homogeneous PAni coatings are obtained on the micro-channel surface while maintaining the nanomorphology of PAni. The optical proprieties of these PAni coatings change in response to the pH of the solution that is flushed inside the micro-channel and therefore can be used for pH monitoring in a wide pH range.
The second type of adaptive coatings contains the photo-chromic molecule spiropyran. Based on the solvatochromic proprieties of the spiropyran unit, these coating can be successfully used to photo-detect solvents of different polarity passing through the capillary. Furthermore, this sensing behaviour can be switched on/off remotely using light, either along the entire length of the capillary, or at patterned locations using appropriate masks.
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