  The efficient and voidless filling of microcavities is of great importance
for Lab-on-a-Chip applications. However, predicting whether microcavities will
be filled or not under different circumstances is still difficult due to the
local flow effects dominated by surface tension. In this work, a close-up study
of the microcavity filling process is presented, shedding light on the
mechanisms of the filling process using experimental insights accompanied by 3D
numerical simulations. The movement of a fluid interface over a microcavity
array is investigated optically under consideration of different fluids,
capillary numbers, and cavity depths, revealing a regime map of different
filling states. Moreover, the transient interface progression over the cavities
is analyzed with attention to small-scale effects such as pinning. Besides the
visual analysis of the image series, quantitative data of the dynamic contact
angle and the interface progression is derived using an automated evaluation
workflow. In addition to the experiments, 3D Volume-of-Fluid simulations are
employed to further investigate the interface shape. It is shown that the
simulations can not only predict the filling states in most cases, but also the
transient movement and shape of the interface. The data and code associated
with this work are publicly available at Bosch Research GitHub and at the
TUDatalib data repository.
