생체모방 나노구조표면의 제조와 이의 접착/마찰 거동에 관한 연구
- 생체모방 나노구조표면의 제조와 이의 접착/마찰 거동에 관한 연구
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- In nature, the extraordinary properties and functions of biological systems always give us a novel paradigm for the design of engineering materials. They also offer remarkable hydrodynamic, aerodynamic, wetting and adhesive properties. In all living organisms, nature provides a multiplicity of materials, architectures, systems and functions. Nature is a school for materials science and its associated disciplines such as chemistry, biology, physics or engineering.
In Chapter 2, releasing one-dimensional (1D) nanoarrays from nanotemplates is a significant challenge for the integration of mechanically soft materials in a variety of newly emerging technological areas. To fabricate nanoarrays without defects, the combined effects of the surface energy and the geometric features of the nanotemplate should be considered. A previously reported approach based on the correlation between the adhesion energy and the real contact area was not satisfactory to describe the rupture conditions of the nanofibers while they were being peeled off of the porous template. Here I demonstrate that the aspect ratio rather than the contact area of the nanoporous template is the key factor determining the upper limit of the pore length of the nanotemplate with respect to rupture of the nanoarray during separation. I propose that the value of , which is calculated with a simple expression in which the adhesion energy is multiplied by the aspect ratio, can be used as an excellent criterion for the fabrication of 1D nanoarrays without defects with simple peel-off processes. My approach opens up new applications for unconventional lithographic techniques, such as soft lithography, imprint lithography, and others.
In Chapter 3, I propose a simple method to fabricate the hierarchical polymeric nanohairs with high aspect ratio using multi-branched anodic aluminum oxide (AAO) template and fiber yielding of polystyrene (PS) material. The multi-branched AAO template was prepared by two-step anodization and barrier layer thinning process and the surface of template was modified by silane with hydrophobic nature. The filled hierarchical nanohairs were elongated upon removal of the template due to adhesive force at the modified template and polymer interface. These nanohairs show excellent adhesion and friction property compared to the single-level nanohair and unstructured samples. Furthermore, this nanohairy surface shows remarkable superhydrophobic property similar to natural gecko foot hairs.
Chapter 4 described the fabrication of a mushroom-like superhydrophobic and highly oleophobic surfaces with a hierarchy. To generate multi-level re-entrant structures on the polymer surface, we have employed both photolithography process and anodic aluminum oxide (AAO) template. This method offers a facile route to prepare re-entrant polymeric structures optimized highly omniphobic properties. Additionally, these structures have the nanopost arrays on the top, thus hierarchical re-entrant texture could enhance the omniphobic properties. A hierarchical mushroom-like polymer structures show excellent superhydrophobic and highly oleophobic property compared to the micropost and unstructured samples.
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