  Cellular elastomeric metamaterials are interesting for various applications,
e.g. soft robotics, as they may exhibit multiple microstructural pattern
transformations, each with its characteristic mechanical behavior. Numerical
literature studies revealed that pattern formation is restricted in (thick)
boundary layers causing significant mechanical size effects. This paper aims to
experimentally validate these findings on miniaturized specimens, relevant for
real applications, and to investigate the effect of increased geometrical and
material imperfections resulting from specimen miniaturization. To this end,
miniaturized cellular metamaterial specimens are manufactured with different
scale ratios, subjected to in-situ micro-compression tests combined with
digital image correlation yielding full-field kinematics, and compared to
complementary numerical simulations. The specimens' global behavior agrees well
with the numerical predictions, in terms of pre-buckling stiffness, buckling
strain and post-buckling stress. Their local behavior, i.e. pattern
transformation and boundary layer formation, is also consistent between
experiments and simulations. Comparison of these results with idealized
numerical studies from literature reveals the influence of the boundary
conditions in real cellular metamaterial applications, e.g. lateral
confinement, on the mechanical response in terms of size effects and boundary
layer formation.
