Photo-Induced Electric Field Effects on Water Droplets Generated in a LiNbO₃ Opto-Microfluidic Platform

In this work, droplets elongation as a result of the photo-induced photovoltaic electric field is presented and modeled. Moving water droplets are generated in microfluidics channels by means of a droplet-based opto-microfluidic platform integrated in lithium niobate (LN). A cross-junction is engraved on the substrate as droplets generator, on top of which a z-cut iron-doped lithium niobate (Fe:LN) crystal is placed in order to build up photo-induced electric field as a result of photovoltaic effect promoted upon suitable illumination. Droplets detection is realized by optical waveguides, designed in a Mach-Zehnder Interferometer (MZI) configuration on the same substrate. The dynamics of droplet elongation is investigated, highlighting the impact of the photovoltaic electric field on the droplet dimension and surface tension.