自然界中的許多生物表面，如蝴蝶翅膀、稻葉與豬籠草的捕蟲籠唇(peristome)都具有多功能潤濕性質，能藉由方向性潤濕引導水流。舉例來說，藉由水流在表面的擴散，豬籠草的捕蟲籠唇表面會變得滑溜，啟動捕捉昆蟲的陷阱。豬籠草唇表面具有方向性潤濕性質的原因在於它特殊的多階層結構與親水性。本研究藉由翻模與表面改質合成啟發自豬籠草唇的方向性潤濕表面，首先使用翻模技術成功以PDMS (polydimethylsiloxane) 複製出豬籠草唇的多階層結構，接著藉由大氣電漿誘發，使PEG (polyethylene glycol) 接枝在PDMS表面，使之由疏水性變為親水性。我們量測其接觸角並透過高速攝影機的拍攝，測量所合成表面的潤濕性與水流動態行為，另外也使用SEM (Scanning Electron Microscope)與XPS (X-ray photoelectron spectroscopy) 定性表面型態與接枝效果。透過結構的設計與表面改質，本研究成功做出可調控潤濕性、高效率、具穩定機械與化學性質的仿生表面，其特殊的方向性潤濕性質將可用於許多領域。

Multi-functional wetting properties was discovered in many species, like butterfly wings, rice leaves, and Nepenthes peristome, which can induce unidirectional wetting to guild the water flow. For instance, water can spread efficiently on the Nepenthes peristome, the rim of insects-capturing pitcher, to induce a slippery surface. The unidirectional wetting behavior of peristome is due to its unique hierarchical structure and intrinsic hydrophilicity. Inspired from Nepenthes peristome, the artificial unidirectional wetting surface was made of PDMS (polydimethylsiloxane) via replication method followed by surface modification. The replica successfully reproduced the hierarchical structure of Nepenthes peristome. Then, to change the wettability of PDMS surface from hydrophobic to hydrophilic, PEG (polyethylene glycol) was grafted on PDMS induced by atmospheric pressure plasma. The wettability and dynamic wetting behavior were evaluated by static contact angle measurements and high speed camera. Surface morphology and grafting quality was characterized by SEM and XPS. Through structural design and surface modification, unidirectional wetting surfaces with tunable wettability, high efficiency, mechanical and chemical stability were successfully synthesized and can be potentially applied in various fields.

List of tables VI
Figure Caption VII
Chapter 1 Introduction 1
Chapter 2 Literature Review 5
2.1 Wetting 5
2.1.1 Classic Wetting Models 5
2.1.2 Super-hydrophilicity in the Wenzel State 6
2.1.3 Anisotropic Wetting and Unidirectional Water Spreading 7
2.1.4 Anisotropic Wetting of Biological Surfaces 9
2.2 Surface Properties of Nepenthes 22
2.2.1 Capture Mechanisms 22
2.2.2 Directional Wetting of Nepenthes Peristome 23
2.3 Replication Method 28
2.4 Surface Modification 33
2.4.1 Atmospheric Pressure Plasma Treatment 33
2.4.2 Polymer Grafting 34
Chapter 3 Experimental methods 39
3.1 Synthesis of Biomimetic Surface 39
3.1.1 Preparation of Biological Surface 39
3.1.2 Replication process 39
3.2 Polymer Grafting Induced by Atmospheric Pressure Plasma Technique 46
3.2.1 Atmospheric pressure plasma treatment 46
3.2.2 Preparation of APTES-grafted PDMS 47
3.2.3 Preparation of PEG-grafted PDMS 47
3.3 Characterization 51
3.3.1 Microstructural Characterization 51
3.3.2 Contact Angle Measurement 51
3.3.3 Electron Spectroscopy for Chemical Analysis (ESCA) 52
3.3.4 Water Flow Behavior Observed by High Speed Camera 52
Chapter 4 Results and Discussion 57
4.1 Hierarchical Structure Replicated from Nepenthes Peristome 59
4.1.1 Microstructure 59
4.1.2 Contact Angle Measurement 59
4.2 Surface Modification by Grafting Hydrophilic Polymers 65
4.2.1 APTES Grafting 65
4.2.2 PEG Grafting 66
4.2.3 XPS analysis of PEG-grafted PDMS 67
4.2.4 Long-term Durability of PEG-grafted PDMS 68
4.3 Dynamic Behavior of Water Flow on PEG-grafted PDMS Replica 76
4.3.1 Unidirectional Wetting Behavior 76
4.3.2 Tilt Test 77
Chapter 5 Conclusions 81
5.1 Wettability of Different Materials with Nepenthes Peristome Structure 81
5.2 Surface Modification by Grafting Polyethylene Glycol (PEG) on Polydimethylsiloxane (PDMS) 82
5.3 Dynamic Wetting Behavior of PEG-grafted PDMS Replica 82
Chapter 6 Future work 83
6.1 Improving the Polymer Grafting Process 83
6.2 Synthesis of Gradient Wetting Surfaces 84
6.3 Synthesis of Larger and Simpler Directional Wetting Surfaces 84

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