Separation of colloidal nanoparticles using capillary immersion forces

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Capillary force assembly (CFA) of colloidal particles usually results in closed-packed films or particle aggregation within topographic features. In this work, it is shown that CFA can also be exploited to both localize and separate nanoparticles (d=50–200nm) when template shape and wettability are controlled. Well-defined geometric arrangements of one to four closely spaced particles (30–50nm separation) were realized in large arrays using this technique to demonstrate that particle aggregation during dewetting can be eliminated. Ordered SiO2 nanopillars in tight groupings were obtained by combining low-resolution e-beam lithography (>100nm) with CFA and etching. This approach provides a simple route to fast and precise placement of nanostructures using relatively low-resolution pattern making techniques.