Curvature Directed Assembly

Colloquium: Prof. Kathleen Stebe, University of Pennsylvania

In materials science, the control over the spatial arrangement of colloids in soft matter hosts
implies control over a wide variety of materials properties, ranging from the system’s rheology,
to its optics, to its catalytic activity. To direct particle assembly, colloids are often manipulated
using external fields to steer them into well-defined structures at given locations. We have
been developing alternative strategies based on fields that arise when a colloid is placed within
soft matter to form an inclusion that generates a potential field in its host. Such potential fields
allow particles to interact with each other. If the soft matter host is deformed in some way,
the potential allows the particles to interact with the global system distortion. The concept is
quite general, and applied within any medium in which distortions cost energy. We have
explored these ideas in three media: curved fluid interfaces, where particles interact with the
host interface via capillarity; confined nematic liquid crystals, where particles interact with the
host director field via elastic interactions, and deformed lipid bilayers, where particles interact
o tense membranes. These example systems have important analogies and pronounced
differences which we seek to understand and exploit.