Fabrication of Liquid Metal-based Deformable Acoustic Devices for Skin-Attachable User Interactive Electronic System
- 주제(키워드) Liquid Metal-based Deformable Acoustic Devices , Skin-Attachable User Interactive Electronic System
- 발행기관 고려대학교 KU-KIST융합대학원
- 지도교수 하정숙
- 발행년도 2020
- 학위수여년월 2020. 2
- 학위구분 박사
- 학과 KU-KIST융합대학원 NBIT융합전공
- 원문페이지 171 p
- UCI I804:11009-000000127505
- DOI 10.23186/korea.000000127505.11009.0000954
- 본문언어 영어
- 제출원본 000046023558
초록/요약
Recently, interest in deformable electronic devices for wearable and bio-implantable systems is rapidly increasing. Numerous kinds of deformable and wearable electronic devices such as actuators, sensors, energy storage and energy harvesting devices have been proposed. Considering the immense range of applications that can be achieved with sound, it would be essential to develop deformable devices for user-interactive wearable systems. Such a system can perform a function of playing music, recoding voice, measuring bio-acoustic signals, hearing aid, or feeding back information to a user while attached to a human body without any limitation of time and space. In order to develop a practical wearable sound system, several requirements should be satisfied. First, all components that configure a wearable acoustic system should be mechanically deformable and durable to maintain performance, because many electronic devices are vulnerable to the strain exerted by the deformation of the skin or joints. Second, in order to develop a skin-attachable device, the performance loss of the device should be minimized in the process of thinning and softening the device. Third, not only the development of flexible acoustic devices, but also their own energy supply devices are needed to drive the systems without wired power supplies. Wired connections to the outside are not suitable for such systems that perform various functions while attached to the skin. In order to satisfy these conditions, we developed deformable acoustic devices using a Gallium-based liquid metal (Galinstan). Galinstan is a eutectic liquid metal in which Gallium, indium and tin are alloyed at specific atomic ratios. Its metallic conductivity and liquid phase properties at room temperature make it an ideal material that satisfies the above conditions of ensuring high deformability and performance simultaneously. High conductivity of Galinstan ensures high performance of the device by minimizing losses due to resistance, while it reversibly deforms in response to external strain to minimize degradation. Deformable acoustic devices using Galinstan are driven by two different principles. The first is a dynamic acoustic device that uses electromagnetic interactions between a magnet and a coil. We have developed a deformable sound source and an acoustic sensor by replacing the non-deformable metal wire coils and peripheral materials with deformable liquid metal coils and elastomers. The second is a liquid metal acoustic device driven by an electrochemical method. It utilizes the movement of liquid metal induced by electrochemically adjustable interfacial tension of Galinstan in a basic electrolyte (NaOH(aq)) environment. Both types of liquid metal acoustic devices emit sound audible to humans in the audible frequency band (20 Hz – 20 kHz). They can also play not only single frequency tone, but also piano sounds, beeper sound of alarm clock and human voices. In addition, the dynamic liquid metal device also functions as a microphone capable of recording external sounds using the principle of electromagnetic induction between the coil and the magnet. Both types of acoustic devices have been successfully driven under external mechanical strain, confirming their applicability to wearable and skin-attachable systems. In addition to the development of the liquid metal acoustic device, the device for supplying energy to the wearable system is also introduced. We have developed a highly durable and flexible transparent electrode (FTE) for a high performance, flexible perovskite solar cell that can be applied to wearable systems. This is because the flexible transparent electrodes, which have both conductivity, transparency and durability, are rare. In particular, low durability of conventional FTE has hampered the development of flexible solar cells by significantly limiting the range of flexible solar cell fabrication processes that can be selected. In order to ensure good durability and performance simultaneously, the materials constituting the flexible transparent conductor and the flexible transparent substrate are carefully selected. As a result, A highly durable FTE is developed by applying a composite consisted of a thin Cr/Au metal grid and a doped conducting polymer (PEDOT:PSS) onto a colorless polyimide-coated NOA63 substrate. The developed electrode has the good performance, heat resistance, acid resistance and processability applicable to the flexible perovskite solar cells. The flexible perovskite solar cell fabricated based on the developed FTE has good performance and durability enough to drive commercial display devices outdoors. In addition to the experimental results and discussions, various background knowledge, measurement methods, and the related theories are included with many references. I expect our research to be the foundation for the development of future acoustic devices with high deformability, thus accelerating the emergence of practical skin-attachable user interactive electronic systems.
more목차
1. Introduction 1
Figures of Chapter 1 5
2. Theoretical Background 9
2.1 Liquid metal-based electronics 10
2.1.1 About Gallium based Liquid metal 10
2.1.2 Application using electrical & mechanical properties of liquid metal 10
2.1.3 Application using electrochemical properties of liquid metal 11
2.2 Strategies for the development of soft acoustic devices using liquid metals 12
2.2.1 Liquid metal acoustic device driven by dynamic principles 12
2.2.2 Liquid metal acoustic device driven by electrochemical principles 14
2.2.3 Performance analysis of elastic acoustic device 14
2.3 Challenges in developing highly durable flexible transparent electrodes 16
2.4 The Strategies for Development of Highly Durable Flexible Transparent Electrodes 17
2.5 Performance and durability evaluation of flexible transparent electrodes 18
Figures of Chapter 2 21
3. Stretchable Loudspeaker Using Liquid Metal Microchannel 36
3.1 Introduction 37
3.2 Experimental details 37
3.2.1 Fabrication of microchannel molds with planar coil patterns 37
3.2.2 Production of deformable elastomer microchannel 38
3.2.3 Fabrication of planar Galinstan coil 38
3.2.4 Wiring and sealing process of the liquid metal coil 39
3.2.5 Fabrication of the dynamic acoustic device 39
3.3 Results and Discussion 40
3.3.1 Electrical stability against mechanical deformation of liquid metal coils 40
3.3.2 Performance of Liquid Metal Acoustic Devices as Sound Sources. 40
3.3.3 Performance of Liquid Metal Acoustic Devices as Sound Sensors. 44
3.3.4 Comparison of the fabricated devices with commercial products 45
3.3.5 Application 46
3.4 Conclusion 47
Figures of chapter 3 49
4. A Flexible Loudspeaker Using the Movement of Liquid Metal Induced by Electrochemically Controlled Interfacial Tension 68
4.1 Introduction 69
4.2 Experimental details 69
4.2.1 Fabrication of A flexible liquid metal loudspeaker (LML) 69
4.2.2 Measurement of acoustic performance of the fabricated LML 70
4.2.3 Electrical characterization of the fabricated LML. 70
4.2.4 Measurements of the interfacial tension and the motion of the liquid metal droplet 71
4.3 Results and Discussion 71
4.3.1 Acoustic performance of the fabricated LML 71
4.3.2 Real-time motion analysis of a Galinstan droplet with electrical characterization. 73
4.3.3 Analysis of the effect of device structure on performance 76
4.3.4 Device flexibility and its application 78
4.3.5 Estimated lifetime of the fabricated device 78
4.3.6 Further analysis and discussion of remaining issues 79
4.4 Conclusion 81
Figures of chapter 4 83
5. Highly Durable and Flexible Transparent Electrode for Flexible Optoelectronic Applications 105
5.1 Introduction 106
5.2 Experimental details 106
5.2.1 Preparation of a NOA63/CPI substrate as a flexible transparent substrate 106
5.2.2 Deposition of Cr/Au grid and EG-PEDOT:PSS as a flexible transparent conductor 107
5.2.3 Converting the fabricated FTE into n-type electrode for FPSC 108
5.2.4 Fabrication of FPSC 108
5.2.5 Preparation of a FPLED 109
5.2.6 Characterization method 109
5.3 Results and Discussion 110
5.3.1 Performance of the produced flexible transparent electrode 110
5.3.2 Durability of the fabricated flexible transparent electrode 111
5.3.3 Modification the FTE into n-type electrode for FPSC applications 113
5.3.4 Application 115
5.4 Conclusion 117
Figures of chapter 5 118
6. Summary 136
7. References 138
8. Acknowledgement 147
