Assembly of Silica Particles at Free Standing Smectic-A Films*

The ability of liquid crystals (LCs) to organize particles into regular structures provides novel routes to control ordering transitions, with the possibility of building complex artificial structures for diverse applications. Since LCs are readily reconfigurable, they offer opportunities to make responsive devices including smart energy-efficient windows, responsive optical components, and sensors. Furthermore, colloidal particles at complex fluid interfaces and within films assemble to form ordered structures via interactions that include capillarity, elasticity, and other fields. Here we study microparticle interactions within free-standing smectic-A films, in which the elasticity arising from the director field distortion and capillary interactions arising from interface deformation compete to direct the assembly of particles. New colloidal assemblies and patterns, ranging from 1D chains to 2D aggregates, sensitive to the initial wetting conditions of particles at the smectic film, are reported. This work paves the way to exploiting LC interfaces as a means to direct spontaneously formed, reconfigurable, and optically active materials.