The tilted-nanohair arrays (TNAs) and tilted-Janusian-nanohair arrays (TJNAs) with the structural and chemical asymmetries are fabricated using a facile two-step process combining Faraday-cage-assisted plasma nanotexturing and plasma polymerization. The directional liquid transport (DLT) against the tilt direction of nanohair and in the reverse direction is achieved on TNAs and TJNAs, respectively. A two-dimension model involving the asymmetric geometry of tilted nanohairs and the related imbibition priority of water meniscus in the inter-nanohair spaces is presented to predict the preferential direction of liquid spreading. Channels with TNAs and TJNAs can be fabricated for exquisite flow control in diverse functional fluidic devices.
Plasma surface engineering technologies recently present an advance in specific surface functionalization of polymer materials, such as the plasma treatment by a reactive or inert gas and the synthesis of plasma polymer coatings from a precursor. Maskless plasma nanotexturing of polymer substrates leads to the formation of various functional nanotextures exemplified by flexible nanowires, rigid nanopillars, slender nanohairs, nanocones and large nanobundles, etc. Plasma polymerization is an efficient one-step process to fabricate new surfaces with controlled amounts of specific chemical functionality at the outer surface of material. Plasma technologies also are flexibly utilized to endow specific biomimetic functionalities on polymer surfaces.
Superior nanometre-scale structures mostly endow the unique properties in natural creatures to adapt the extremely harsh living environments. The cicada and drangonfly wings with the nanocone and the nanopillar structures, respectively, display excellent antireflection and antiwetting properties. In this work, the biomimetic nanocones and nanopillars on various polymer substrates inspired by cicada and drangonfly wings were fabricated by the combination of the plasma etching and the plasma polymerization deposition. The natural crystalline state and degree of different polymer materials could have obvious effect on the size and distribution of nanostructures. All polymer surfaces with nanocones and nanopillars demonstrated the reduced reflectance over the visible and near-infrared spectrum compared with the pristine surfaces. The weaker angle dependence of reflectance was achieved for the surfaces with nanocones. The surfaces with nanocones and nanopillars exhibit also superhydrophobicity due to the plasma polymerization deposition of fluorocarbon film. The stable superhydrophobicity of the nanocones and nanopillars with the Cassie state was found in waterdrop-impact experiments. The nanocone arrays exhibit better anti-warterdrop impacting ability than the nanopillars. The nanocones and nanopillars on flexible and curved polymeric materials enhance the superhydrophobicity showing reduce of the impalement probability and the contact time of waterdrops. The plasma nanotexturing methods composed of the plasma etching and the plasma polymerization deposition could be appropriate to fabricate biomimetic nanostructures of cicada and drangonfly wings on the polymer substrates.
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