Transport of fluids and particles at the microscale is an important theme
both in fundamental and applied science. One of the most successful approaches
is to use an electric field, which requires the system to carry or induce
electric charges. We describe a versatile approach to generate electrokinetic
flows by using a liquid crystal (LC) with surface-patterned molecular
orientation as an electrolyte. The surface patterning is produced by
photo-alignment. In the presence of an electric field, the spatially varying
orientation induces space charges that trigger flows of the LC. The active
patterned LC electrolyte converts the electric energy into the LC flows and
transport of embedded particles of any type (fluid, solid, gaseous) along a
predesigned trajectory, posing no limitation on the electric nature (charge,
polarizability) of these particles and interfaces. The patterned LC electrolyte
exhibits a quadratic field dependence of the flow velocities; it induces
persistent vortices of controllable rotation speed and direction that are
quintessential for micro- and nanoscale mixing applications.Comment: 35 pages, 10 figure
