Small-volume refractive index and fluorescence sensor for micro total analytical system (μ-TAS) applications

A novel single point waveguide device for small-volume refractive index (RI) and fluorescence emission detection for micro total analytical system (μ-TAS) applications has been fabricated and tested. These metal clad leaky waveguide (MCLW) devices were fabricated using silica as the leaky waveguiding layer in combination with diffraction grating coupling elements and an injection moulded flow-channel structure. These devices have been designed in order to increase the overlap between the extension of the evanescent field at the channel wall and the materials within the channel in the sensing layer. These devices can be used to detect the channel contents by monitoring the resonance angle at the liquid-waveguide interface, these variations are evidenced through changes of the decoupling angle measured using liner CCD. The waveguide was tested by irrigating the sensor surface with glycerol solutions (0–10% (w/v) glycerol in water) and with fluorescein solutions (10−13 to 10−7 M). The limit of detection was determined to be 10−13 M for fluorescein solution.