Monitoring of DNA molecules in a lab on a chip with femtosecond laser written waveguides

Using femtosecond laser writing, optical waveguides were monolithically integrated into a commercial microfluidic lab-on-a-chip device, with the waveguides intersecting a microfluidic channel. Continuous-wave laser excitation through these optical waveguides confines the excitation window to a width of 12 um, enabling high-resolution monitoring of the passage of different types of fluorescent analytes, when migrating and being separated in the microfluidic channel by microchip capillary electrophoresis. We demonstrate on-chip-integrated waveguide excitation and detection of a biologically relevant species, fluorescently labeled Deoxyribonucleic acid (DNA) molecules, as well as separation of different dyes, Rhodamine-6G and Rhodamine-B during microchip capillary electrophoresis. Well-controlled plug formation as required for on-chip integrated capillary electrophoresis separation of DNA molecules, and the combination of waveguide excitation and a low detection limit will enable monitoring of extremely small quantities with high spatial resolution.