We present a simple technique to
switch off the tack adhesion in
selected areas of a colloidal nanocomposite adhesive. It is made from
a blend of soft colloidal polymer particles and hard copolymer nanoparticles.
In regions that are exposed to IR radiation, the nanoparticles sinter
together to form a percolating skeleton, which hardens and stiffens
the adhesive. The tack adhesion is lost locally. Masks can be made
from silicone-coated disks, such as coins. Under the masks, adhesive
island regions are defined with the surrounding regions being a nontacky
coating. When optimizing the nanocomposite’s adhesive properties,
the addition of the hard nanoparticles raises the elastic modulus
of the adhesive significantly, but adhesion is not lost because the
yield point remains relatively low. During probe–tack testing,
the soft polymer phases yield and enable fibrillation. After heating
under IR radiation, the storage modulus increases by a factor of 5,
and the yield point increases nearly by a factor of 6, such that yielding
and fibrillation do not occur in the probe–tack testing. Hence,
the adhesion is lost. Loading and unloading experiments indicate that
a rigid skeleton is created when the nanoparticles sinter together,
and it fractures under moderate strains. This patterning method is
relatively simple and fast to execute. It is widely applicable to
other blends of thermoplastic hard nanoparticles and larger soft particles
