  We study theoretically and experimentally the solvent-mediated critical
Casimir force acting on colloidal particles immersed in a binary liquid mixture
of water and 2,6-lutidine and close to substrates which are chemically
patterned with periodically alternating stripes of antagonistic adsorption
preferences. These patterns are experimentally realized via microcontact
printing. Upon approaching the critical demixing point of the solvent, normal
and lateral critical Casimir forces generate laterally confining effective
potentials for the colloids. We analyze in detail the rich behavior of the
spherical colloids close to such substrates. For all patterned substrates we
investigated, our measurements of these effective potentials agree with the
corresponding theoretical predictions. Since both the directions and the
strengths of the critical Casimir forces can be tuned by minute temperature
changes, this provides a new mechanism for controlling colloids as model
systems, opening encouraging perspectives for applications.
