I. INTRODUCTION
The patterns formed in dewetting processes have attracted strong interest since Reiter analysed the
process quantitatively in the early nineties. In these experiments, that proved to be a paradigm in
our understanding of dewetting, a uniform thin ﬁlm of polystyrene (tens of nanometers thick) is
deposited on a ﬂat silicon oxide substrate is brought above the glass transition temperature. The
ﬁlm ruptures in several places, forming holes which subsequently grow, competing for space. As a
result, a random polygonal network of liquid rims emerges. The rims may further decay into lines
of small drops due to a Rayleigh-type instability [1–3]. The related problems of retracting contact
lines on partially wetting substrates and the opening of single holes in rather thick ﬁlms have also
been studied [4, 5].
Subsequent work has mainly focused on many different aspects of the dewetting process for simple
non-volatile liquids and polymers (for reviews see Refs. [6–8]). All stages of the dewetting of a
ﬁlm are studied: the initial ﬁlm rupture via nucleation or a surface instability (called spinodal
dewetting) [1, 9–13], the growth process of individual holes [14–16], the evolution of the resulting
hole pattern [3, 13], and the stability of the individual dewetting fronts [17–19]. We note in
passing, that descriptions of dewetting patterns may also be found in historic papers, particularly
for the dewetting of a liquid ﬁlm on a liquid substrate. Tomlinson [20, footnote 18 on p. 40]
considered turpentine on water and Marangoni [21, p. 352f] oil on water.
More recently, interest has turned to the dewetting processes of solutions and suspensions. How-
ever, these systems have not yet been investigated in any great depth. Such systems are compli-
cated because their behaviour is determined by the interplay between the various solute (or colloid)
and solvent transport processes. Furthermore, the solvents that are used often evaporate, i.e., one
has to distinguish between ‘normal’ convective dewetting and evaporative dewetting. A number
of experiments have been performed employing (colloidal) solutions of polymers [22–25], macro-
molecules like collagen and DNA [26–31] and nanoparticles [32–40]. The latter are sometimes
referred to as ‘nanoﬂuids’. The initial focus of much of the research in the ﬁeld has been on
investigating the structures that are formed which are similar to the ones observed in the ‘classi-
cal’ dewetting of non-volatile liquids. Labyrinthine structures and polygonal networks result from
spinodal dewetting and heterogeneous nucleation and growth, respectively. They are ‘decorated’
with the solute and therefore conserve the transient dewetting pattern as a dried-in structure when
all the solvent has evaporated [28, 34]. The picture is, however, not complete. The solute may
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