A scalable fibre-optic sensing architecture for lab-on-a-chip devices

Advancements in continuous and digital microfluidics (DMF) for integrated optics technologies are improving the feasibility of biophotonic sensors within lab-on-a-chip devices. Lab-on-a-chip diagnostic devices are achieving unprecedented high levels of throughput. Digital microfluidics, with its reconfigurable nature, is often utilized over continuous microfluidic systems due to reagent economy, precision, potential for scalability, and independent fluid actuation. However, scalability within DMF systems is currently inhibited by the DMF sensing architectures that are presently used, being capacitance and resistance sensing. These electrical- based sensing architectures probe each microdroplet location and this is difficult to scale. In this work, a fibre-optic sensing architecture is developed to improve scalability and achieve independent sensing of microdroplets. The sensing architecture utilizes an m x n (column and row) perpendicular overlap grid structure of embedded fibre-optic cables that yields m x n sensing positions with m + n measurement points. To evaluate both localized and practical scalability of the system, actuation contact time and differentiation of multiple microdroplets are assessed. The embedded fibre-optic cables will distribute light proportional to the number of microdroplets in contact along the column or row. Differentiation of multiple microdroplets is assessed with a theoretical model and through experimental measurements. The DMF sensing architecture is demonstrated for a three by three grid with multiple microdroplets present. The results show compatibility with high-speed DMF operation (due to fast contact times) and demonstrate scalable sensing of multiple microdroplets.