This paper examines self-assembly in a quasi-two-dimensional, mesoscale system. The system studied
here involves hexagonal plates (“hexagons”) of poly(dimethylsiloxane) (PDMS; 5.4 mm in diameter, 0.9−2.0
mm thick), with faces functionalized to be hydrophilic or hydrophobic, floating at the interface between
perfluorodecalin (PFD) and H2O. The hexagons assemble by capillary forces originating in the interactions of
the menisci at their hydrophobic and hydrophilic rectangular faces. The strength and directionality of the
interactions can be tailored by manipulating the heights of the faces, the pattern of the hydrophobic faces, the
pattern of hydrophobic regions on these faces, and the densities of the three interacting phases (organic liquid,
aqueous liquid, polymeric solid). Examination of all 14 possible combinations of hydrophobic and hydrophilic
faces on the hexagonal plates led to three outcomes: (i) the extension of the strategies of self-assembly from
the molecular to the mesoscale, (ii) the demonstration of a system in which small objects can be designed to
self-assemble into a variety of arrays, and (iii) the hypothesis that capillary forces between objects can, in
some circumstances, be considered to form the basis for a “bond” between themthe capillary bondand be
used in synthesis in a way analogous to that in which noncovalent bonds are employed in molecular-scale
synthesis.