An integrated fluorescence array as a platform for lab-on-a-chip technology using multimode interference splitters

We present the design and fabrication of 1-to-N multimode interference (MMI) splitters, suitable for use in integrated optical fluorescence array sensing, with particular applications in lab-on-a-chip (micro-TAS) technologies. Electron beam irradiation of germanium-doped flame hydrolysis deposited silica was used to define the MMI waveguide regions. The splitters were integrated with microfluidic channels to form direct-excitation fluorescence sensor chips for use at visible wavelengths. Characterization of the waveguides shows that predictable splitting ratios can be achieved. Two devices are presented: a 1×2 splitter integrated with one analytical chamber and a 1×4 array device for multipoint excitation. A photomultiplier tube was used to assess the analytical performance of the chip, in response to standard aliquots of fluorophore (31 nM to 1.25 μM).