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A Miniaturized, Eye-conformable, and Long-term Reliable Retinal Prosthesis using Monolithic Fabrication of Liquid Crystal Polymer (LCP) : 액정폴리머를 기반의 소형, 안구밀착형, 장기안정적인 인공망막장치

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dc.contributor.advisor김성준-
dc.contributor.author정준수-
dc.date.accessioned2017-07-13T07:09:59Z-
dc.date.available2017-07-13T07:09:59Z-
dc.date.issued2015-08-
dc.identifier.other000000053362-
dc.identifier.urihttps://hdl.handle.net/10371/119099-
dc.description학위논문 (박사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2015. 8. 김성준.-
dc.description.abstractA novel retinal prosthetic device was developed using liquid crystal polymer (LCP) to address the problems associated with conventional metal- and polymer-based devices: the hermetic metal package is bulky, heavy and labor-intensive, whereas a thin, flexible and MEMS-compatible polymer-based system is not durable enough for chronic implantation. Exploiting the advantageous properties of LCP such as a low moisture absorption rate, thermo-bonding and thermo-forming, a small, light-weight, long-term reliable retinal prosthesis was fabricated that can be conformally attached on the eye-surface. A LCP fabrication process using monolithic integration and conformal deformation was established enabling miniaturization and a batch manufacturing process as well as eliminating the need for feed-through technology. The fabricated 16-channels LCP-based retinal implant had 14 mm-diameter with the maximum thickness of 1.4 mm and weight of 0.4 g and could be operated wirelessly up to 16 mm of distance in the air.
The long-term reliability of the all-LCP retinal device was evaluated in vitro as well as in vivo. Because an all-polymer implant introduces intrinsic gas permeation for which the traditional helium leak test for metallic packages was not designed to quantify, a new set of reliability tests were designed and carried out specifically for all-polymer implants. Moisture ingress through various pathways were classified into polymer surface, polymer-polymer and polymer-metal adhesions each of which were quantitatively investigated by analytic calculation, in vitro aging test of electrode part and package part, respectively. The functionality and long-term implantation stability of the device was verified through in vivo animal experiments by measuring the cortical potential and monitoring implanted dummy devices for more than a year, respectively. Samples of the LCP electrodes array failed after 114 days in 87°C salin as a result of water penetration through the LCP-metal interface. An eye-confirmable LCP package survived more than 35 days in an accelerated condition at 87°C. The in vivo results confirmed that no adverse effects around the retina were observed after implantation of the device for more than a year.		-
dc.description.tableofcontentsABSTRACT i
Contents iv
List of Figures xi
List of Tables xxi

Chapter 1 : Introduction 1
1.1. Neuroprosthetic devices 1
1.2. Retinal prosthesis 2
1.2.1. Concept 2
1.2.2. Three approaches 3
1.2.3. Camera vs. Photodiode 4
1.3. Conventional devices 5
1.4. Liquid Crystal Polymer (LCP) 7
1.4.1. Low moisture absorption and permeability 9
1.4.2. Thermoplastic property 9
1.4.3. Compatibility with MEMS technologies 10
1.4.4. RF characteristics 10
1.5. LCP-based retinal prosthesis 11
1.6. Long-term reliability 12
1.7. Dissertation outline 14

Chapter 2: Methods 16
2.1. System Overview 16
2.2. Microfabrication on LCP 18
2.2.1. Limitations of the previous microfabrication technique on LCP 19
2.2.2. Improved LCP-based microfabrication 22
2.2.2.1. Electroplated micro-patterning 23
2.2.2.2. Laser-thinning for higher flexibility 24
2.2.2.3. Laser-ablation for site opening 25
2.3. All-LCP Monolithic Fabrication 26
2.3.1. Multilayered integration 29
2.3.1.1. Electrical components 29
2.3.1.2. Thermal lamination 32
2.3.1.3. Layer configuration 34
2.3.2. Thermal deformation 35
2.3.2.1. Deformation process 35
2.3.2.2. Wavy lines for stretchability 36
2.3.2.3. Electrical properties of the deformed coil 40
2.3.3. Circuit Assembly 40
2.3.3.1. Stimulation ASIC 40
2.3.3.2. Surrounding circuitries 41
2.3.4. Packaging 43
2.3.5. Laser Machining 44
2.4. Device characterization 44
2.4.1. Transmitter Circuit and Wireless Operation 45
2.4.1.1. Transmitter circuit 45
2.4.1.2. Transmitter coil 46
2.4.1.3. Wireless operation test 46
2.4.2. Electrochemical measurements 48
2.5. Long-term reliability tests in vitro 49
2.5.1. Failure mechanisms of an all-LCP device 49
2.5.2. Analytic calculation 51
2.5.3. Long-term reliability tests in accelerated environment 55
2.5.3.1. Long-term reliability of electrode array 55
2.5.3.2. Long-term reliability of package 57
2.5.3.3. Long-term reliability of complete device 58
2.5.4. Long-term electrochemical stability 59
2.6. Acute and Chronic Evaluation in vivo 60
2.6.1. Surgical implantation 60
2.6.2. Acute functionality test 62
2.6.3. Long-term implantation stability 63

Chapter 3: Results 64
3.1. Microfabrication on LCP 64
3.1.1. Electroplated micro-patterning 64
3.1.2. Laser-ablation for site opening 67
3.1.3. Laser-thinning for higher flexibility 69
3.2. All-LCP Monolithic fabrication 71
3.2.1. Multilayered integration 71
3.2.2. Thermal deformation 73
3.2.2.1. Deformation results 73
3.2.2.2. Wavy lines for stretchability 74
3.2.2.3. Effect on the electrical properties 74
3.2.3. Circuit assembly 76
3.2.4. Packaging 77
3.2.5. Laser machining 79
3.3. Device Characterization 80
3.3.1. General specifications 81
3.3.2. Transmitter circuit and coil 83
3.3.3. Wireless operation 83
3.3.4. Electrochemical measurements 84
3.4. Long-term reliability tests in vitro 86
3.4.1. Analytic calculation 87
3.4.2. Long-term reliability tests in accelerated condition 90
3.4.2.1. Long-term reliability of electrode arrays 90
3.4.2.2. Long-term reliability of package 92
3.4.2.3. Long-term reliability of complete device 93
3.4.3. Long-term Electrochemical stability 93
3.5. Acute and chronic evaluation in vivo 95
3.5.1. Surgical implantation 95
3.5.2. Acute functionality test 96
3.5.3. Long-term implantation stability 97

Chapter 4: Discussion 100
4.1. Comparison with conventional devices 100
4.2. Potential applications 102
4.3. Opportunities for further improvements 102
4.4. Long-term reliability 104

Chapter 5: Conclusion 108
Reference 110
국문초록 118
감사의 글 121		-
dc.formatapplication/pdf-
dc.format.extent5013577 bytes-
dc.format.mediumapplication/pdf-
dc.language.isoen-
dc.publisher서울대학교 대학원-
dc.subjectretinal prosthesis-
dc.subjectliquid crystal polymer-
dc.subjectneural prosthesis-
dc.subjectconformable-
dc.subjectmonolithic integration-
dc.subject.ddc621-
dc.titleA Miniaturized, Eye-conformable, and Long-term Reliable Retinal Prosthesis using Monolithic Fabrication of Liquid Crystal Polymer (LCP)-
dc.title.alternative액정폴리머를 기반의 소형, 안구밀착형, 장기안정적인 인공망막장치-
dc.typeThesis-
dc.contributor.AlternativeAuthorJOONSOO JEONG-
dc.description.degreeDoctor-
dc.citation.pagesxxii, 125-
dc.contributor.affiliation공과대학 전기·컴퓨터공학부-
dc.date.awarded2015-08-
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