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국회도서관 홈으로 정보검색 소장정보 검색
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Title Page

초록

Abstract

Contents

Chapter 1. Introduction 13

1.1. Wearable devices 13

1.2. Strain Sensor 14

1.2.1. The basic mechanism of the strain sensor 15

1.2.2. Carbon Nanomaterials 16

1.2.3. Carbon nanotubes 17

1.2.4. Graphene 18

1.2.5. Metal nanoparticles with the high aspect ratio 19

1.3. Energy harvesting devices 19

1.3.1. Triboelectric nanogenerator 19

1.4. Soft-lithography 21

1.5. Scope of the thesis 23

1.6. References 24

Chapter 2. Enhanced sensitivity of strain sensor by transferring patterned graphene layer 32

2.1. Introduction 32

2.2. Experimental Section 34

2.2.1. Preparation of the GNP/PSS dispersion and PVA solution 34

2.2.2. Fabrication of the patterned PMMA films 34

2.2.3. LbL assembly process 35

2.2.4. Sensor fabrication 35

2.2.5. Characterization 35

2.3. Results and Discussion 36

2.4. Conclusion 51

2.5. References 52

Chapter 3. Ultra-sensitive strain sensor by utilizing zigzag-shaped silver nanoplates 56

3.1. Introduction 56

3.2. Experimental details 57

3.2.1. Chemicals and Materials 57

3.2.2. Synthesis of Zigzag-shaped Ag Nanoplates 58

3.2.3. Fabrication of Strain Sensors 58

3.2.4. Characterizations 59

3.3. Results and Discussion 59

3.4. Conclusion 79

3.5. References 79

Chapter 4. Well-ordered patterning of polymer film for triboelectric generator application 86

4.1. Introduction 86

4.2. Experimental Section 87

4.2.1. Synthesis of Polystyrene Colloidal Particles 87

4.2.2. Fabrication of 3D Colloid-Crystal Master Molds 87

4.2.3. Preparation of the PDMS Replica Mold 87

4.2.4. Patterning PMMA Films and PDMS Films 88

4.2.5. Device fabrication and characterization 88

4.3. Results and Discussion 89

4.4. Conclusion 98

4.5. References 99

Chapter 5. Concluding Remarks 101

Curriculum Vitae 104

List of Tables

Table 1.1. Triboelectric series for some common materials following a tendency of easy losing electrons... 20

Table 3.1. Selected parameters extracted from recently reported papers on strain sensors fabricated from... 70

Table 4.1. Size measurement results of synthesized PS particles and fabricated PMMA patterns and the... 94

List of Figures

Figure 1.1. Surface sensors need to be as flexible and stretchy as the skin they are mounted on. 14

Figure 1.2. Basic mechanism of strain sensors (A) normal, (B) stretched and (C) compressed... 15

Figure 1.3. Carbon nanomaterials with their modification for the various applications 17

Figure 1.4. Schematic illustration of the four major steps involved in soft lithography and three... 22

Figure 2.1. (a) Photograph of the PSS-stabilized GNP which is dispersed in DI water, and (b)... 34

Figure 2.2. Steps in the fabrication of the patterned graphene strain sensor. (a) A PMMA film... 36

Figure 2.3. Optical microscopy image of the patterned PMMA film 37

Figure 2.4. (a) Photograph of GNP-coated PMMA films formed by LbL assembly. (b) SEM... 38

Figure 2.5. Sheet resistance of the GNP-coated PMMA film as a function of the number of BLs. 39

Figure 2.6. (a) A GNP-coated PMMA film is attached to a Petri dish using double-sided... 40

Figure 2.7. Schematic illustration of sensor fabrication after transferring GNP layer. (a) A... 41

Figure 2.8. Plots of (a) RRC and (b) GF of the patterned graphene strain sensors with graphene... 42

Figure 2.9. Resistance of the graphene strain sensors versus applied strain at different numbers... 42

Figure 2.10. (a) Photograph of graphene strain sensors with (left) and without (right) patterning.... 43

Figure 2.11. Schematic illustration of the piezoresistivity of the sensors induced by thickness... 44

Figure 2.12. (a) RRCs and (b) GF of non-patterned graphene strain sensors prepared through... 45

Figure 2.13. Schematic illustration of the possible electric current paths (yellow arrows) in the... 45

Figure 2.14. SEM images of the GNP layers (3 BLs) on PDMS, transferred from (a) the non-... 46

Figure 2.15. RRCs in graphene sensors with (a) 2, (b) 3, (c) 5, and (d) 7 BLs upon repeated... 47

Figure 2.16. RRC of the graphene sensor with 3 BLs as a function of applied strain up to 10 %,... 47

Figure 2.17. (a) Applied strain (blue) and measured resistance (black) of the patterned graphene... 48

Figure 2.18. (a-c) OM images of the GNP layer, which is sandwiched by the PDMS layer,... 48

Figure 2.19. Photographs of the graphene strain sensors (a) with and (b) without patterning of... 49

Figure 2.20. Photograph of a large graphene strain sensor. 49

Figure 2.21. (a) Photograph of a patterned graphene strain sensor strapped to a wrist to monitor... 51

Figure 3.1. (a-c) TEM images and (d) XRD pattern of Ag nanoplates grown in the presence of... 61

Figure 3.2. Two representative AFM images and height profiles of the zigzag-shaped Ag... 62

Figure 3.3. High-resolution TEM images, taken from the flat top faces of one of the nanoplates... 63

Figure 3.4. High-resolution TEM images, taken from the flat top faces of several nanoplates... 64

Figure 3.5. TEM images of synthesized Ag nanoplates as denoted as (a) polygonal Ag... 65

Figure 3.6. (a) Schematic illustration of the fabrication of the Ag nanoplate strain sensor. (b)... 67

Figure 3.7. SEM images of Ag nanoplate thin films comprised of zigzag-shaped Ag nanoplates... 68

Figure 3.8. Gauge factors of the fabricated Ag nanoplate strain sensors as a function of the... 69

Figure 3.9. Gauge factors as a function of maximum stretchability extracted from recently... 71

Figure 3.10. (a) TEM and (b) SEM images of Ag nanowires used in the present study,... 72

Figure 3.11. Schematic illustration of the strain sensor including (upper panel) high aspect ratio... 73

Figure 3.12. SEM top view image of the Ag nanoplate sensors based on zigzag-shaped Ag... 74

Figure 3.13. SEM images with different magnifications that show the microstructures of the... 75

Figure 3.14. Schematic illustrations for percolation network through islands after stretching in... 76

Figure 3.15. (a) Impulse response test by applying the drum beating sound with frequency of... 77

Figure 3.16. (a) Photographs (left) and ∆R/R0 response (right) of our fabricated Ag nanoplate...(이미지참조) 78

Figure 4.1. SEM images of PS particles with the sizes of (a) 800 nm, (b) 1200 nm, (c) 1600... 89

Figure 4.2. Schematic illustration of experimental procedure 90

Figure 4.3. AFM images of patterned triboelectric layers with the four different sizes; PDMS... 91

Figure 4.4. SEM top images of patterned PMMA film, fabricated from the PDMS replica mold... 92

Figure 4.5. Schematic illustration of patterned structure from (a) 3 μm particles and (b) 1.5 μm... 92

Figure 4.6. Illustration of patterned region, estimated from the AFM data 94

Figure 4.7. (a) Illustration of assembling TENG with indication by the color (upper panel) and... 95

Figure 4.8. (a) Voc and (b) Jsc of the assembled TENG devices and (c) durability test for 1600...(이미지참조) 96

Figure 4.9. Overall mechanism of assembled TENG device 97

Figure 4.10. (a) Maximum voltage peaks (black line) and current densities (red line) of... 97

Figure 4.11. (a) Assembled TENG device was connected with the rectifier for converting... 98

초록보기

최근 웨어러블 기기의 등장 이후로 전자 제품 및 부품의 소형화 및 유연화에 대한 많은 기술의 발전이 이뤄지고 있다. 특히 기존에 사용되고 있는 금속 또는 세라믹 반도체기반의 무기소재들은 높은 밀도와 그 자체의 딱딱한 특징으로 인하여, 가볍고 유연한 탄소나노소재, 전도성 고분자 등 신소재의 활용에 대한 관심이 증가하고 있다. 이러한 신소재들을 실제 공정에 적용하기 위해서는 소프트 리소그래피와 같은 용액 공정을 기반으로 하여 대면적 공정을 위한 소재 선택 및 기능화가 필요하다. 본 학위논문에서는 유연한 고분자를 기반으로 하여 용액 공정의 장점을 활용하여 다양한 웨어러블 소자를 제작하고자 하였다. 특성 조절이 용이한 용액공정을 통해 전도성 소재를 가공, 제작하고, 전사 혹은 패터닝 공정을 이용하여 유연한 소재에 적용한 결과, 기존보다 향상된 특성을 보이는 웨어러블 센서 및 에너지추출 소자의 제작이 가능하였다. 실제로 제작된 소자들은 그 특성을 조절이 가능하였으며 저전력에서 구동되는 웨어러블 기기에 적합하도록 최적화가 가능하였다.

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