Title Page
Abstract
Contents
Chapter 1. Introduction 11
1.1. Study background 11
1.2. Previous researches 13
1.3. Objective and overview of this study 16
Chapter 2. Preparation and Method 20
2.1. Material Preparation 20
2.2. Fabrication Process 23
2.3. Measurement and Analysis 26
Chapter 3. System Design and Optimization 29
3.1. Schematic and operating mechanism 29
3.2. Thermoelectric semiconductor 31
3.3. Optimizing the Design Parameters of Thermoelectric Pellets 32
3.4. Highly Thermally Conductive Elastomer 35
Chapter 4. Characterization and Performance Evaluation of Device 44
4.1. Active Mode for Accurate Thermal Control 44
4.2. Mechanical Reliability of the Device against Various Stress 52
4.3. Visualization Expression based on CIE1931 54
Chapter 5. Thermally Controlled Camouflageable Device 57
5.1. Contribution of Thermal Pixels 57
5.2. Multispectral Cloaking Performance 58
5.3. Active Camouflage Artificial Skin 62
Chapter 6. Conclusions 65
REFERENCES 66
국문 초록 70
Figure 1-1. Cross-sectional schematic of cephalopod skin showing their complex skin cells' architecture, which embedded pigment granule-packed chromatophore... 12
Figure 1-2. Previously developed representative biological-inspired camouflaging devices. (a) Early suggested visible and thermal cloaking soft device by using the... 15
Figure 1-3. Snapshots of cephalopod under the visible-to-infrared spectrum. This indicates the instantaneous camouflage ability of cephalopods to blend into the... 18
Figure 2-1. 3D visual illustrations of the device comprising thermochromic ink, Cu electrode, ahighly thermally conductive elastomer, and thermoelectric pellets,... 21
Figure 2-2. Simplified schematic representation of the cloaking device fabrication procedure. 24
Figure 2-3. The cause for mechanical failure after stretching for different bonding materials. (a) Image of thermoelectric pellets bonded to Cu electrode using different... 25
Figure 2-4. An experimental setup for night-time camouflage with IR view of (a) the heating and (b) cooling mode on skin. Note that the heating mode of the device... 27
Figure 3-1. Schematic representation of the device (a) A Single unit schematic that shows the device can actively cool down or heat up to camouflage in the... 30
Figure 3-2. The effect of temperature on figure of merit (ZT value)of p-type and n-type thermoelectric materials. 32
Figure 3-3. The effect of the thermoelectric pellet height on performance. (a) Numerically simulated result. (b) Experimentally conducted result. 34
Figure 3-4. The effect of the thermal conductivity of elastomer. (a) Numerical simulated result of pristine elastomer. (b) Thermal conductivity measurement... 36
Figure 3-5. Material schematics of the highly thermally conductive elastomer (HTCE). Note that synthesized silver plate is electrically conductive in the in-plane... 37
Figure 3-6. Thermal conductivity measurement and stretching test with the varying number of layers. (a) In-plane and cross-plane thermal conductivity of anisotropic... 38
Figure 3-7. The experiment result of the device performance in perspective of thermal uniformity. (a) Comparison between highly thermally conductive elastomer... 40
Figure 3-8. The transient temperature change and its corresponding IR/optical snapshots for the heating and cooling modes at each current increase. 42
Figure 4-1. Comparison of thermal response time and controllability between (a) slow passive mode and (b) fast active mode 45
Figure 4-2. Electrical current change for the fast active mode and passive slow mode. Note that for the fast active mode the electrical current follows a step-wise... 47
Figure 4-3. The detail data view of slow passive mode and fast active mode when the device displaying red color in figure 4.1. (a) The magnified initial head and (b)... 49
Figure 4-4. Overlapped graphs of the fast active mode and slow passive mode in cycles to demonstrate the high responsiveness of the fast active mode. 50
Figure 4-5. The IR images and temperature comparison on approaching target temperature above and below the room temperature between (a) slow passive mode... 51
Figure 4-6. Cyclic temperature change in which cooling and heating modes alternated in cycles with ΔT = 40 ℃. Note that the IR and optical images after the... 52
Figure 4-7. Cyclic bending test during which the 1 × 5 device was repetitively bent while recording electrical resistance to examine the mechanical robustness... 53
Figure 4-8. CIE 1931 diagram which maps the discrete colors (indicated as black-star points) expressed with the device at different thermal profiles. The series of the... 55
Figure 5-1. Thermal display displaying visible and IR letters A, N, T in visible colors and S, N, U in various temperature. 58
Figure 5-2. Schematic representation of the two different designs. (a) The polymer materials (HTCE) in between pixels serve to transfer heat and thus possibly result in... 59
Figure 5-3. Multispectral cloaking in the visible and IR regimes on the virtual map, in which the device worn on the hand moves across different visible and thermal... 61
Figure 5-4. Actual demonstration of multispectral imperceptible artificial skin worn on half of the face for military stealth application. The pixelization of the device... 63