There is an ever increasing need for methods to perform chemical reactions involving individual molecules, or small molecular assemblies in applications ranging from single enzyme dynamics to molecular electronics. To meet these demands, a transition from traditional 3D, to 2D or 1D reactor systems that reduces the dimensionality, and hence exponentially reduces the number of interacting particles would be beneficial. Low-dimensional systems, unlike bulk ensembles, exhibit some degree of order and can be made on small foot-prints using nanofabrication techniques. However, whereas chemistry can easily be performed in e.g. test tubes, and droplets, initiating and controlling chemistry with the same ease on planar surfaces has been a tremendous challenge. We here present a 2D micro-/nano-fluidic technique with such a capability, and where reactant-doped molecular liquid crystal lipid films spread and mix on patterned amphiphilic substrates. These substrates can be micro- and nanopatterned photoresist, or even micropatterned Teflon. Eventually, all reactants are present in two dimensions, mimicking a situation in the lipid bilayer of cells or cell compartments. Phospholipid monolayer films are spread and contain complementary DNA strands modified with a lipophilic anchor and with a fluorescent dye. By using resonance energy transfer, we monitor the hybridization of the complementary strands, and are able to detect the double-stranded DNA in flowing streams on lanes as small as 250 nm wide, with as few as 900 molecules in the cross section. Our results show that the density and number of different reactants, can be controlled within liquid crystal films confined to patterned substrates. The technology introduced here provides a platform for nanochemistry with the potential for kinetic control where molecules with 2D orientational order can be synthesized, controlled, routed, and probed. Therefore, this technology could become a model system for dynamic biological surfaces.
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