Atomic Layer Deposition Reinforcement of Methylcellulose Nanowire Forests

Micro‐ and nanostructured surfaces are widely used as functional surfaces in various fields including the maritime and medical industries. Many micro‐ and nanocoating technologies are delicate processes that have high costs at scale. Herein, an electrospray deposition (ESD) technique is investigated as an affordable method for obtaining micro/nanostructured surfaces. When processed via ESD from water:ethanol blends, methylcellulose (MC), a fibril gel former, can form nanowire coatings. These nanowires are formed via enhanced gelation by shear forces and surface charges that lead to electrospinning on a drop‐by‐drop basis. However, these ESD MC nanostructures can be easily destroyed upon water exposure. In this work, conformal coating of these MC nanostructures with atomic layer deposition (ALD) of Al₂O₃ is explored to impart further stability. Upon subsequent heating of the ALD‐coated MC nanostructures, superhydrophobicity can be obtained. It is found that the final ALD‐coated structures exhibit a trade‐off between mechanical stability and hydrophobicity depending on MC nanowire size, with smaller wires being more mechanically robust and larger wires being more hydrophobic.