Directional Clustering of Slanted Nanopillars by Elastocapillarity

A strategy to induce the directional clustering of nanopillars by controlling their tilted angles was proposed. Regularly spaced nanopillar arrays with different tilted angles of 0°, 15°, 30°, and 45° was prepared and their clustering was demonstrated by dispersing and drying a deionized water droplet on them. By observing their clustering patterns, a simple model was developed to explain the features of tilted-angle-dependent clustering, and a criterion was proposed to classify the continuity of clustering. It was observed that the tilted-angle-dependent clustering of nanopillar arrays after drying the water droplet. It was noncontinuous and island-like with 0°?and 15° tilt, but continuous and unidirectional with 30° and 45° tilt. The designed asymmetric, directional clustering of tilted nanopillars would be applicable to the directional self-assembly of high aspect ratio nanostructures and directional transport of specific materials.