Enhanced sensing to characterize microdroplets through induced optical phenomena in integrated opto-microfluidic lab-on-a-chip

This research reports concept, realization and testing of an opto-microfluidic lab-on-a-chip fully integrated in lithium niobate. Such a device aims at the integration between optical sensing and microfluidics, a perspective with many fields of application like micro-analytical chemistry and biomedical analysis. The integration is achieved herein by arranging several parallel waveguides with a T-junction of two micrometric channels on the same LiNbO3 surface. While the Tjunction enables the generation of microdroplets of a liquid sample, light can be brought to the channel by the waveguides once one of them is lighted from its input. Thanks to this configuration, an intensity signal can be collected through the waveguides to a photodiode, resulting in the detection of a time signal linked to the shape and composition of the flowing microdroplets. In this research, after introducing the detection process, particular attention is paid to the experimental test of the device sensing performance. As an example, the light absorption due to the introduction of a protein dispersion in a concentration reactive dye is reported. By comparing two droplet classes of different content and same shape, the two related mean signals are clearly discriminated, showing a significant sensitivity enhancement for two different protein concentrations. These results prove the device as a fully efficient system for content analyses, merging low consumption of the liquid sample with an effective detection strategy.