  Many biological systems can form strong adhesion to various materials with
complex shapes. The adhesion is further switchable between strongly adhering
and completely non-adhering in a simple and fast manner. By contrast, no
engineering system has yet achieved the same robust adherence and switching.
This limitation severely hinders the advancement of several emerging
technologies including biomimetic robots, assembly-based manufacturing,
precision medicine, wearable and implantable devices, as well as on-demand
material dismantling and recycling for sustainability. Here we present a design
approach for strong and highly switchable adhesion by synergizing the surface
stickiness, bulk energy dissipation, and stimuli-responsive polymer chains in a
thermo-switchable soft sticky adhesive. The adhesive has a high adhesion
strength of about 80 kPa with diverse materials at room temperature. The
adhesion is highly switchable to near-vanishing (about 0.6 kPa) at an elevated
temperature due to the thermo-responsive surface polymer chain retraction. This
adhesion switching is reversible and repeatable for many cycles, enabling
selective pick-and-release of objects with various materials, shapes, sizes,
and weights. The switching time is around 10 s with an adhesive layer of 1 mm,
governed by thermal conduction through the adhesive, faster than or comparable
to most state-of-the-art methods. The adhesive is self-healing, and can be
recycled, dried, stored, reswollen, and reused with nearly intact adhesion and
switching properties. The synergistic design combining strong adhesion and
stimuli-responsive switching can be potentially extended to various polymer
systems, and further enhanced by optimized surface architectures.
