  We present an isogeometric collocation method for solving the biharmonic
equation over planar bilinearly parameterized multi-patch domains. The
developed approach is based on the use of the globally $C^4$-smooth
isogeometric spline space [34] to approximate the solution of the considered
partial differential equation, and proposes as collocation points two different
choices, namely on the one hand the Greville points and on the other hand the
so-called superconvergent points. Several examples demonstrate the potential of
our collocation method for solving the biharmonic equation over planar
multi-patch domains, and numerically study the convergence behavior of the two
types of collocation points with respect to the $L^2$-norm as well as to
equivalents of the $H^s$-seminorms for $1 \leq s \leq 4$. In the studied case
of spline degree $p=9$, the numerical results indicate in case of the Greville
points a convergence of order $\mathcal{O}(h^{p-3})$ independent of the
considered (semi)norm, and show in case of the superconvergent points an
improved convergence of order $\mathcal{O}(h^{p-2})$ for all (semi)norms except
for the equivalent of the $H^4$-seminorm, where the order
$\mathcal{O}(h^{p-3})$ is anyway optimal.
