Imaging of unlabelled bacteria at a sensor surface using aluminium-clad integrated waveguide chips

An aluminium-clad leaky waveguide was integrated into a miniaturized chip also containing the required flow geometry and optical coupling elements in a robust device that is relatively simple and inexpensive to fabricate. A leaky waveguiding approach is used to generate a region of very intense interrogating illumination that penetrates ~1 μm into the sample layer before decaying rapidly to zero. This enables the detection of unlabelled, non-fluorescent micron-scale particles and bacteria of similar dimensions, by the capture of scattered light resultant from interactions with the intense leaky guided mode. Such interactions occur only at the waveguide/sample interface and not within the bulk of the sample. This device therefore represents a potentially effective platform for rapid and selective bacterial detection in combination with the appropriate binding procedures. © 2004 IOP Publishing Ltd.