Nanobiophotonics

Digital droplet-based bioassays (ddAssays) have been applied in numerous fields, though many existing microfluidic platforms are tailored to specific assay classes and require complex workflows involving multiple processing steps. Here, we present a fully integrated microfluidic platform for generic digital bioassays that combines droplet generation and storage for on-chip incubation and optical readout on a single disposable device. This microfluidic platform enables the parallel execution of test and control experiments, each using more than 200 000 monodisperse droplets of 35 pL. CFD simulations of the step emulsification unit, together with experimental characterization, confirm the predicted device performance. The device is prepared by variothermal compression molding. A dual-layer photoresist strategy was used to create the master for replicating the channel systems with two different channel heights and step transitions between them. The core functionality and the applicability of various optical modalities for image-based readout are demonstrated by exemplary biochemical and microbial growth reporter assays. The platform is compatible with automated image-based analysis for high-throughput digital assay readout.