  We study the critical Casimir force for a film geometry in the Ising
universality class. We employ a homogeneous adsorption preference on one of the
confining surfaces, while the opposing surface exhibits quenched random
disorder, leading to a random local adsorption preference. Disorder is
characterized by a parameter p, which measures, on average, the portion of the
surface that prefers one component, so that p=0, 1 correspond to homogeneous
adsorption preference. By means of Monte Carlo simulations of an improved
Hamiltonian and finite-size scaling analysis, we determine the critical Casimir
force. We show that by tuning the disorder parameter p, the system exhibits a
crossover between an attractive and a repulsive force. At p=1/2, disorder
allows to effectively realize Dirichlet boundary conditions, which are
generically not accessible in classical fluids. Our results are relevant for
the experimental realizations of the critical Casimir force in binary liquid
mixtures.
