In-situ optical spectroscopy on nanoporous silicon thin films and photonic crystals for high spatial resolution in imbibition experiments

Nanoporous silicon is investigated for sensing applications in a variety of fields. Combinations of layered structures and porosity modulations are among others used to improve the sensing performance. In view of the fluidics inside nanopores a combination of a thin film interference layer followed by a photonic crystal unlocks much more than that. ^[1] In-situ optical spectroscopy of capillary imbibition into this structure allows the observation of fluid front broadening, the liquid meniscus and ultra-thin precursor films at micro-second resolution. The method compares local and collective filling dynamics by differentiating in between optical features. Overall, we introduce an exceptionally precise technique for fluid and in particular polymer characterization inside nanopores on a chip.