  Thin films made of deformable micro- and nano-units, such as biological
membranes, polymer interfaces, and particle-laden liquid surfaces, exhibit a
complex behavior during drying, with consequences for various applications like
wound healing, coating technologies, and additive manufacturing. Studying the
drying dynamics and structural changes of soft colloidal films thus holds the
potential to yield valuable insights to achieve improvements for applications.
In this study, we employ interfacial monolayers of core-shell microgels with
varying degrees of softness as model systems and investigate their drying
behavior on differently modified solid substrates (hydrophobic vs.
hydrophilic). By leveraging on video microscopy, particle tracking, and thin
film interference, we shed light on the interplay between microgel adhesion to
solid surfaces and the immersion capillary forces that arise in the thin liquid
film. We discovered that a dried replica of the interfacial microstructure can
be more accurately achieved on a hydrophobic substrate relative to a
hydrophilic one, particularly when employing softer colloids as opposed to
harder counterparts. These observations are qualitatively supported by
experiments with a thin film pressure balance which allows mimicking and
controlling the drying process and by computer simulations with coarse-grained
models.
