  We present an investigation of the role of micropatterning on adhesion
properties at soft deformable polydimethylsiloxane (PDMS)/ acrylic adhesive
interfaces. Contrary to what has been observed for low aspect ratio rigid
patterns, where the adhesion enhancement was found to only result from the
increase of interfacial area due to patterning, we show that for soft elastic
arrays of cylindrical pillars, the elastic deformation of the patterns can lead
to noticeable extra adhesion increase. The effect of the geometrical
characteristics of the patterning for hexagonal arrays of PDMS micropillars on
the adhesion energy are presented. We show that varying the size of the pattern
allows one to tune the adhesion energy, and that this adhesion enhancement
saturates when the pillars become too close to each other, due a coupling of
the elastic deformation fields inside the underlying substrate. A mechanical
model has been developed and found in good quantitative agreement with
experimental data, with as unique fitting parameter the rupture criteria for
the adhesive on the top of the pillars. Such a rupture a rupture criteria can
thus be extracted from systematic experiments on controlled patterned surfaces.
This criteria remain sensitive to the chemistry of the surfaces.
