There is a tremendous progress in both the scientific understanding and applications of self-assumblies of small particles. Forming superstructures in which particles of different nature occupy presdeisnged sites represents a major challenge of the current state-of-the art. We proposed a versatile approach to direct placement of mocroparticles using nematic liquid crystals with spatially varuing molecular orientation pre-imposed bu photo-alignment [1]. The particles are sbukect to elastic forces originating in the orientational order of the nematic that drive them into predesigned locations as shown in the figure. This development is the first step to sort mocroparticles according to their surface properties, wchich is of importance in sensing and "lab on a chip" devices.
[1] C. Peng et al, Control of colloidal placement and assembly by modulated molecular orientation in nematic cells, Science Advances 2, e1600932 (2016); the paper was invited to the special issue of Science Advances on Materials by Design.