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소장정보 검색

국회도서관 홈으로 정보검색 소장정보 검색
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Title Page

Contents

Abstract 11

Chapter 1. Introduction 13

1.1. Background and rationale 13

1.2. Structure of thesis 15

References 18

Chapter 2. Theoretical background 20

2.1. Introduction 20

1) Polymers 20

2) Inorganic-based materials 23

2.2. Thin film instability 24

2.2.1. Hydrodynamic 25

2.2.2. Interfacial pressure 29

2.2.3. Linear stability analysis and dispersion relation 33

2.3. Electrohydrodynamic instability 34

2.4. Surface wettability 38

1) Surface chemistry 40

2) Surface roughness 41

2.5. Conclusion 44

References 45

Chapter 3. Experimental preparations and analytical techniques 49

3.1. Sample preparation 49

3.1.1. Preparation of precursor solutions 49

3.1.2. Substrate cleaning 51

3.1.3. Spin coating 52

3.2. High voltage EHD process 53

3.3. Characterizations 54

3.3.1. AFM analysis 54

3.3.2. SEM Analysis 55

3.3.3. Contact angle measurement 56

3.4. Conclusion 57

References 58

Chapter 4. Pillar structure Formation 60

4.1. Introduction 60

4.2. EHD-induced pillar structure formation 61

1) Basic concept of pillar structure formation 61

2) Influence by air gap 62

3) Low voltage vs. high voltage 63

4.3. Aspect ratio controlled by film filling ratio 66

1) Theory 66

2) Results and discussions 67

4.4. Tuning the surface wettability 69

1) Surface wettability by resulting pillars 69

2) Application: Pattern transfer on non - traditional substrates 71

4.4. Templated-assisted EHD-induced patterns 74

1) Secondary instability 75

2) Results and discussion 78

4.6. Conclusion 78

References 80

Chapter 5. Conclusions 82

5.1. Conclusions 82

5.2. Future research 83

References 85

List of Tables

Table 2.1. Properties of organic materials 50

Table 2.2. Properties of inorganic materials 50

List of Figures

Figure 2.1. Schematic illustration of thin film instability on substrate. Surface fluctuations with wavelength λ＝2π/q. The velocity profile υ for... 26

Figure 2.2. Schematic illustration of the polarized dielectric in the electric field. The electrostatic pressure resulting due to opposing charges by the applied... 36

Figure 2.3. Schematic diagram of relationship between the contact angle and the interfacial surface energies 39

Figure 2.4. Wetting states explained by (a) Wenzel model and (b) Cassie-Baxter model. 42

Figure 4.1. Schematic illustrations for overview process (a) Pillar growth induced by the external electric field over time (b) Pattern film transferred assisted by... 61

Figure 4.2. Optical images for pillar pattern evolution influenced by air gap (a) Spatiotemporal evolution of pillar formation over time with the air gap... 64

Figure 4.3. Surface wettability corresponding to their surface roughness (a) Interplay of filling ratio applied by the uniform electric field determines the... 70

Figure 4.4. Peeling and transferring process (a) Schematic representation for the peeling process (b) Sacrificial layer between pillar and substrate all dissolves... 72

Figure 4.5. Pillar film transferred on non-conventional substrates (a) PDMS, PET, Lens (b) Transferred thin film still have hydrophobic property by the water... 74

Figure 4.6. Formation of secondary instability (a) Photographic image of line patterned master stamp (b) Line pattern s are replicated with the low voltage... 75

Figure 4.7. Surface wettability corresponding to their surface roughness (a) Interplay of filling ratio applied by electric field determines the final geometry... 76

Figure 4.8. Peeling and transferring process (a) Schematic representation for the peeling process (b) Sacrificial layer between pattern and substrate all dissolves... 77

초록보기

 Lithography has come a long way in recent years, with many innovative methods being developed for creating micro and nanostructures in thin films. Despite the progress, most processes still involve multiples steps that can be time-consuming and high cost. Among these lithographic methods, electrohydrodynamic method is the most cost-effective method that is promising for the replication of numerous patterns with high-fidelity features over a large area.

The electrohydrodynamic (EHD) method is a process that creates structures using external electric field to control the flow of thin film. The thin fluid film in the capacitor device of the EHD process is fully driven towards the top electrode by the induced instabilities, leading to creating the desired structures in a small amount of time. Carefully controlling the parameters of the process leads to the production of a wide range of patterns simple line to complex structures with high uniform and precise patterns. The development of surface structures with controlled patterns has become increasingly important for enhancing surface properties of materials with potential applications.

What' s more, the use of unique structures on non-traditional substrates like flexible materials has opened up new possibilities such as flexibility and compatibility with wearable devices. The direct pattern transfer methods have certain limitations that must be taken into consideration. One such limitation is the requirement of conformal contact; the pattern can become damaged during the process. Instead of the traditional pattern transfer method, capillary peeling method is a trustworthy method to transfer unique surface structures on irregular surfaces without any conformal contact.

In this study, we report the combination of electrohydrodynamic patterning for high fidelity features and the capillary transfer method for transferring patterns on the desired surface, that address the current limitations in creating patterns on non-conventional substrates. By altering the electrode gap in the EHD patterning process, the density and shape of patterns can have a significant impact on the properties of the surface like wettability. With further research and development, coupling EHD-induced structures with the pattern transfer method can lead to potential applications in a variety of fields.

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