Creating regular matrices of aligned silica nanohelices: theory and realization

Here we exercise nanoscale control over the assembly of highly anisotropic silica helices using convective flow by using the physical properties occurring during evaporation-induced self-assembly. Organizing and patterning such chiral elongated objects over large surfaces in a controllable and reproducible fashion is challenging, but desirable to opti-mize the performance of biomimetic structures, nano-sensors (mechanical properties of helices) or optical materials (chiral objects have asymmetric interactions with light as absorption is different for left- and right-handed polariza-tion). The coupling of evaporation forces and physicochemical solution properties induce specific orientation of the helices and the stick-slip phenomenon produces a periodical deposition of bands with controllable and regular spac-ing. Helix orientation, packing density and spacing can then be tuned. We observe the effect of polymer additives, silica helix concentration, and substrate withdrawal speed on the quality and the or...