我們報導一種類似空氣卻可以撐住水滴的「釘床」，此二階奈米結構是由兩種奈米結構所組成，其中奈米草提供了超疏水程度的接觸角，而奈米柱則降低了水滴在奈米草上的阻力。對奈米柱間隔 5 m 的試片而言，超過 99.98% 的表面都是由空氣組成，卻能夠支撐 234 Pa 的壓力。由於極低的固體比例與高穩定性，此類空氣表面展現了近乎完美的超疏水特性－具有接近 180 度的接觸角與 0 度的滾動角。

We report an air-like “bed of nails” that supports a drop of water without impalement by fabricating the two-tier superhydrophobic structures comprising two types of nanoscale features: a nanograss that provided a large water contact angle (157°) and nanopillars that reduced the stickiness of the water drop on the nanograss. These nanograsson-
nanopillar structures exhibited robust air-like surfaces. For the structure featuring a pillar separation of 5  m, 99.98% of the surface was composed of air, yet the structure could still support a water droplet subjected to a pressure of 234 Pa. Because of their very low solid fractions and high robustness, these air-like surfaces exhibit near-perfect superhydrophobicity－that is, water contact angles close to 180° and sliding angles close to 0°.