  The wettability of surfaces determines their antifouling, antifogging,
anti-icing, and self-cleaning properties as well as their usability for
sensing, oil-water separation, water collection, and water purification.
Solvent-free high-temperature capillary stamping of stimuli-responsive polymers
yielding arrays of stimuli-responsive polymer microdots on differently modified
substrates enables the flexible generation of switchable surfaces with
different water contact angles (WCAs). Potential problems associated with the
deposition of polymer solutions, such as the handling of volatile organic
solvents, phase separation induced by solvent evaporation, and
capillarity-driven flow processes, are circumvented. We used composite stamps
with topographically patterned contact surfaces consisting of metallic nickel
cores and porous MnO2 coatings taking up the stimuli-responsive polymers. The
short transport paths from the MnO2 contact layers to the counterpart
substrates enabled the stamping of polymer melts containing components impeding
flow, such as carbon nanotubes (CNTs). Thus-obtained arrays of polymer-CNT
hybrid microdots prevent problems associated with continuous coatings including
delamination and crack propagation. Moreover, the range within which the
properties of the stamped stimuli-responsive polymer microdots are switchable
can be tuned by orthogonal substrate modification. As an example, we stamped
hybrid microdots consisting of poly(2-(methacryloyloxy)ethyl
ferrocenecarboxylate) (PFcMA) and CNTs onto indium tin oxide (ITO) substrates.
Coating the ITO substrates with a poly(ethylene oxide)-terminated silane
shifted the WCAs obtained by switching the PFcMA between its oxidized and
reduced states by nearly 50{\deg}.
