Graphene based flexible strain sensor for wearable device

학위논문 (석사)-- 서울대학교 대학원 : 공과대학 기계항공공학부, 2019. 2. 이정훈.최근 로보틱스와 웨어러블 기기, 헬스케어 관련 분야에서의 높은 활용 가능성으로 인해 변형률 센서 연구가 활발히 이루어지고 있다. 나노와이어, 나노 입자, 탄소나노튜브 및 그래핀을 비롯한 다양한 소재로 유연하고 민감한 변형률 센서에 대한 연구가 진행되고 있다. 그 중에서도 그래핀은 높은 전도성, 유연성 및 기계적 강도로 인해 많은 주목을 받고 있다. 본 연구에서는 그래핀 기반 유연한 변형률 센서의 친환경적 공정 및 패터닝 방법에 대해 다룬다. 그리고 제작된 센서를 이용하여 물체와의 거리를 인식하고 물체의 표면 형상을 재구성하는 실험을 수행하였다.Recently, strain sensors have been actively studied due to their high utilization potential in robotics, wearable devices, and health care related fields. Many researchers are working on a variety of materials including nanowires, nanoparticles, carbon nanotubes(CNTs), and graphenes to fabricate these flexible and sensitive strain sensors. Among them, graphene is attracting much attention due to its high conductivity, flexibility and mechanical strength. In this study, we tried to maximize the advantages of graphene - based strain sensor by studying human - friendly manufacturing method and easy patterning process. Experiments were carried out to recognize the distances to objects and to reconstruct the shapes of the objects by analyzing the signals using the produced graphene - based strain sensors.국문초록 i 목차 ii 그림 목차 iii 제 1 장 서론 1 제 1 절 연구배경 1 제 2 절 작동 원리 5 제 2 장 Graphene coating 7 제 1 절 Stencil method 7 제 2 절 Layer by Layer coating method 12 제 1 절 Inkjet printing method 14 제 3 장 Reduction process 19 제 1 절 Flash reduction 19 제 2 절 Chemical reduction 20 제 4 장 Discussion 21 제 1 절 Fabrication protocol 21 제 2 절 Result 23 제 5 장 Conclusion 26 참고문헌 27 Abstract 29Maste

Effects of low temperature deuterium annealing on electrical properties at SiSiO₂ interface

학위논문(석사) --서울대학교 대학원 :전기. 컴퓨터공학부,2007.Maste

The Development of real-time image enlargement/ reduction module for G4 fax

Maste

Antitumor efficacy of hypoxia and alpha-fetoprotein-dependent oncolytic adenovirus and systemically injectable adenovirus-liposome hybrid vector

의과학과/박사종양 선택적 살상 adenovirus(Ad) 는 기존의 복제 불능 Ad보다 치료 효과 및 유전자 전달효율이 높게 나타남에 따라 암 유전자 치료의 새로운 치료제로 연구가 활발히 진행 중이다. 이에 따라, 본 실험실에서는 E1B19 kDa 이 제거된 살상 Ad(Ad-∆E1B19)를 개발하여 강력한 세포 살상효과를 보고한 바 있다. 하지만, Ad-∆E1B19는 암세포뿐 만 아니라 정상세포까지 살상하는 한계가 드러났다. 따라서 본 연구에서는 간암 세포 특이적인 세포 살상 효과를 획득하기 위해 향상된 human alpha-fetoprotein (hAFP) promoter를 Ad의 복제를 조절하는데 사용하였다. 또한 종양 내의 저산소 환경에서 promoter의 활성을 증가시키기 위해 6 또는 12 copies의 hypoxia response element(HRE)를 삽입하여 hAFP promoter 또는 HREs/hAFP 에 의해 E1A 발현이 조절되는 종양 선택적 살상 Ad를 제작하였다. HRE12가 삽입된 Ad-HRE12/hAFP∆19는 대조군인 Ad-hAFP∆19과 비교하여 향상된 종양 선택성과 세포 살상능을 나타냈다. 비침습성 분자 영상으로 Ad-HRE12/hAFP∆19의 종양 살상능을 관찰하였을 때 피하모델과 원발성 간암 모델 모두에서 생체 외 결과와 일치하게 증대된 종양 선택성과 종양 성장 억제능을 나타냈다. 또한, 종양의 조직학적 실험을 진행하였을 때 저산소 지역에서 바이러스의 복제가 활발히 일어나는 것을 확인하였다. 아울러 Ad-HRE12/hAFP∆19를 정맥주사 한 생쥐에서는 심각한 면역반응, 간 독성 또는 조직 독성이 관찰되지 않았다. 이러한 결과들을 바탕으로 본 연구에서는 hAFP promoter와 HREs가 삽입된 Ad-∆E1B19는 향상 된 간암 조직 특이성과 종양 환경 선택성을 나타내는 것을 검증하였다. 따라서 증대된 선택성과 종양 살상능을 가진 Ad-HRE12/hAFP∆19는 AFP를 발현하는 간암에 효과적인 치료제가 될 것으로 사료된다. 그러나 원발암이나 전이암을 치료하기 위한 목적으로 정맥 주사를 통한 Ad의 전달은 체내에 존재하는 Ad에 대한 항체에 의해 치료효과가 떨어진다. 뿐만 아니라 간에 대한 높은 친화력으로 인해 간 이외의 원하는 암 조직에는 전달이 용이하지 않은 단점을 가지고 있다. 이러한 점을 극복하고자 본 연구에서는 비 바이러스성 벡터인 liposome에 Ad의 DNA를 삽입하여 hybrid 벡터를 제작하였다. 사용된 DNA는 HRE와 변형된 TERT promoter에 의해 E1A 단백질이 조절 되고, 분비되는 TRAIL 단백질을 발현함으로서 암세포 살상능과 선택성이 증대 된 Ad DNA(H5mT-Rd19/stTR)이며 폐암을 표적화 하는 DOTAP :DOPE 또는 PEG:DOTAP:DOPE를 liposome으로 이용하여 Ad DNA와 liposome이 1:6의 비율로 혼합된 약 150 nm의 size를 갖는 hybrid 벡터를 제작하였다. Hybrid 벡터는 폐암세포에서 선택적인 세포 살상능을 나타냈으며, 생쥐에 정맥주사 하였을 때 면역반응과 간 독성은 관찰되지 않았다. 이러한 결과를 통해 Ad DNA-liposome hybrid 벡터는 국소적인 암 치료뿐 아니라 전이 암의 치료제로서 유용하게 이용될 수 있을 것으로 사료된다.ope

미세 가공된 대류전자 기반 테르헤르츠 장치에 대한 실험 연구

학위논문(박사)--서울대학교 대학원 :자연과학대학 물리·천문학부,2016. 8. 박건식.For the last decade, terahertz waves have been the focus of many researches to lead to a diverse range of potential applications, such as bio-medical imaging systems, security inspection systems, material analysis systems, and high-data-rate communications systems. Though many types of terahertz components have been developed, e.g., terahertz antennas, filters, guides, and detectors, realistic terahertz applications remain rare due to the lack of powerful, efficient, practically sized, inexpensive, and stable terahertz sources which would fill the terahertz gap. While time-domain spectroscopy (TDS) systems are the main streams of terahertz sources due to the instant spectroscopic capabilities throughout the terahertz range, vacuum electronic devices (VEDs) have also garnered interest due to their high-power capabilities resulting from the high kinetic energy of their convection electrons. In this dissertation, 0.1 THz coupled cavities backward wave oscillator (CCBWO) is proposed and studied as preliminary research on terahertz VEDs, applying two-step LIGA as well as ultra nano CNC machining. The circuits are fabricated with less tolerance than a micron and the cold measurements are in excellent agreement with numerical simulation. All other components of the 0.1THz CCBWO system such as 12kV, 50mA electron gun, 2800gauss of PPM, 8% of band center frequency transmitting vacuum window, and -9kV depressed collector are designed, fabricated, and experimented and all the results match strongly to the design. All parts are assembled together and with the bias voltage at beam focusing electrode, desired perveance is observed in the beam test. 0.22THz staggered extended interaction oscillator is also investigated, focusing on the strong interaction even with relatively low voltage. In the half π phase shifted double grating resonator, The large fraction of the fundamental TE mode is longitudinally polarized, and it excites the intense plasma-terahertz wave coupling at the shallow grating, which enables highly efficient RF generation at a relatively low operating voltage. A particle-in-cell (PIC) simulation predicts that the half-period phase-staggered grating resonator generates 0.22 THz wave with output power exceeding 100 W and interaction efficiency of more than 15 % at a low beam acceleration voltage of 5.2 kV.Chapter 1 Introduction 1 1.1 Terahertz 1 1.1.1 THz gap 2 1.1.2 Present THz sources 4 1.2 Vacuum Electronic Devices (VEDs) 6 1.3 Terahertz VEDS and problems 10 1.4 Motivation and Goal 10 1.5 Outline 11 Bibliography 13 Chapter 2 Experimental study of 0.1THz Coupled Cavities Backward Wave Oscillator (CCBWO) 19 2.1 Introduction 19 2.2 0.1THz CCBWO circuit 20 2.2.1 Design of 0.1THz CCBWO circuit 20 2.2.2 Two step LIGA fabrication 35 2.2.3 Ultra-Nano machining 37 2.2.4 Cold test of 0.1THz CCBWO circuit 42 2.3 Electron gun 45 2.3.1 Design of electron gun 45 2.3.2 Fabrication of electron gun 50 2.3.3 Beam-emission test 56 2.4 Periodic Permanent Magnet (PPM) focusing 58 2.4.1 Design of PPM 60 2.4.2 Fabrication of PPM 63 2.4.3 Measurement of PPM 65 2.5 Wide band width anti-reflecting vacuum window 67 2.5.1 Transmission analysis of pillbox window 69 2.5.2 Design of broadband width of 0.1THz vacuum window 79 2.5.3 Cold test of 0.1THz vacuum window 83 2.6 Depressed collector 85 2.6.1 Design of depressed collector 86 2.6.2 Fabrication of depressed collector 88 2.7 System assembly of 0.1THz CCBWO 92 2.7.1 RF test of 0.1THz CCBWO 98 2.8 Conclusion 99 Bibliography 100 Chapter 3 Theoretical study on 0.22 THz sheet beam staggered Extended Interaction Oscillator (sEIO) 102 3.1 Introduction 102 3.2 Design of 0.22THz sEIO 103 3.2.1 sEIO – Powerfully modified EIO 103 3.3 Particle-In-Cell (PIC) numerical hot test 108 3.4 Conclusion 119 Bibliography 120 Chapter 4 Conclusion 121 List of Publications 122 Domestic Conference proceedings and abstracts 128 국문 초록 130Docto

Design of a Fault Tolerant Multilayer Perceptron Neural Network Minimizing the Effect of Quantization

Docto

파형 제어된 2주기 미만 광 펄스에 의한 고체 및 기체 내 전자 역학의 극초고속 제어와 관측

DoctorMeasurement and manipulation of electron dynamics is a flourishing area of research which catches attention nowadays. Fundamental phenomena, in which electrons are involved, such as electron transition between bands in condensed matter and energy states in atoms, mostly occur at femtosecond or sub-femtosecond time scale. The observation and control of electrons’ behavior has been facilitated owing to the utmost development of laser technology. In this thesis, one of the state-of-the-art light sources, waveform-controlled sub-2-cycle optical laser, was employed to explore the interaction with media in solid and gas phases. In a study with solid media, semimetallization was observed in dielectric crystals subjected to strong laser field. A current was generated and directed by the instantaneous light field. A series of theoretical calculation, based on quadruple sub-band model, showing good agreement with experiment, implies that the semimetallization was brought about by electron transition between and within valence and conduction sub-bands. Semimetallization was observed to be a general response of dielectrics to intense light field. It is accounted for by Wannier-Stark localization, a confinement of electrons in a unit cell of crystal lattice under strong field; the effect of long range crystal structure becomes less important. On the other hand, for a study with gaseous medium, an instrument for single-isolated attosecond pulse, which permits one to trace sub-femtosecond electron dynamics, was constructed. By means of high harmonics generation, a train of XUV attosecond pulses were produced and then underwent spectral filtering to select single XUV burst. The temporal profile of the XUV pulse was attained by analyzing the photoelectron kinetic energy spectrogram, ensuring the generation of a single-isolated attosecond pulse. The attosecond pulse was utilized to examine the AC Stark splitting of noble gas atom exposed to intense light field. The attosecond transient absorption spectroscopy was applied to xenon atoms exposed to an NIR intensity of ~1013W/cm2. The asymmetric AC Stark splitting (or, in other words, Autler-Townes splitting) and sub-cycle oscillation in absorption lines were revealed. Theoretical estimation relying on TDCIS, which was in accordance with experimental findings, asserted that the counter rotating wave effect is responsible for the observation

A cyclic RGD-coated peptide nanoribbon as a selective intracellular nanocarrier

We have synthesized a peptide-based supramolecular building block consisting of a cyclic Arg-Gly-Asp (cRGD) peptide segment and a beta-sheet-forming peptide segment. The block peptide was shown to self-assemble into a cRGD-coated nanoribbon structure, as revealed by circular dichroism (CD), dynamic light scattering (DLS), and transmission electron microscopy (TEM) studies. We have shown that this cRGD-coated nanoribbon can encapsulate hydrophobic guest molecules and deliver them into cells. Colocalization of the nanoribbon with LysoTracker and the selective intracellular delivery results suggests that the cRGD-coated nanoribbon is likely to be internalized into the cells through integrin receptors.ope

Ionically crosslinked Ad/chitosan nanocomplexes processed by electrospinning for targeted cancer gene therapy

For effective cancer gene therapy, systemic administration of tumor-targeting adenoviral (Ad) complexes is critical for delivery to both primary and metastatic lesions. Electrospinning was used to generate nanocomplexes of Ad, chitosan, poly(ethylene glycol) (PEG), and folic acid (FA) for effective FA receptor-expressing tumor-specific transduction. The chemical structure of the Ad/chitosan-PEG-FA nanocomplexes was characterized by NMR and FT-IR, and the diameter and surface charge were analyzed by dynamic light scattering and zeta potentiometry, respectively. The average size of Ad/chitosan-PEG-FA nanocomplexes was approximately 140 nm, and the surface charge was 2.1 mV compared to -4.9 mV for naked Ad. Electron microscopy showed well-dispersed, individual Ad nanocomplexes without aggregation or degradation. Ad/chitosan nanocomplexes retained biological activity without impairment of the transduction efficiency of naked Ad. The transduction efficiency of Ad/chitosan-PEG-FA was increased as a function of FA ratio in FA receptor-expressing KB cells, but not in FA receptor-negative U343 cells, demonstrating FA receptor-targeted viral transduction. In addition, the transduction efficiency of Ad/chitosan-PEG-FA was 57.2% higher than chitosan-encapsulated Ad (Ad/chitosan), showing the superiority of FA receptor-mediated endocytosis for viral transduction. The production of inflammatory cytokine, IL-6 from macrophages was significantly reduced by Ad/chitosan-PEG-FA nanocomplexes, implying the potential for use in systemic administration. These results clearly demonstrate that cancer cell-targeted viral transduction by Ad/chitosan-PEG-FA nanocomplexes can be used effectively for metastatic tumor treatment with reduced immune reaction against Ad.ope

Enhanced delivery of adenovirus, using proteoliposomes containing wildtype or V156K apolipoprotein A-I and dimyristoylphosphatidylcholine

The delivery of genes or viruses via liposomes is a common approach used to enhance delivery efficiency. In the current study, to enhance delivery efficiency, proteoliposomes (PLs) containing adenovirus (Ad) were synthesized with dimyristoylphosphatidylcholine (DMPC), cholesterol, and apolipoprotein A-I (apoA-I). Wildtype apoA-I (WT) or V156K-apoA-I (V156K) was then used as an apolipoprotein to compare the structural and functional differences of the PLs. The particle diameter of V156K-PL-Ad was slightly larger than that of WT-PL-Ad, based on native gel electrophoresis. V156K showed more rapid phospholipid bilayer formation than did the WT, based on DMPC clearance. In addition, V156K exhibited maximal fluorescence that was more blue than that of WT in the PL state. Moreover, isothermal denaturation in response to the addition of guanidine hydrochloride (Gnd-HCl) revealed that V156K was more resistant, with no denaturation until 3 M Gnd-HCl was added. In addition, electron microscopy revealed that the viral particles were well associated with PL particles, which had a discoidal structure and were shaped like rouleaux. In addition, treatment of Ad in the PL state showed enhanced green fluorescent protein (GFP) expression when compared with treatment with Ad alone or with DMPC-Ad in hepatoma and brain glioma cells. Cells treated with WT-PL-Ad and V156K-PL-Ad showed approximately 50% more GFP expression than cells treated with Ad alone or with DMPC-Ad after 24 hr of incubation at 37 degrees C, indicating that viral stability was highly increased in the PL state. Furthermore, V156K-PL-Ad showed the highest expression of GFP in adult zebrafish (9 weeks old) at 5 days postinjection (10.5- and 3.8-fold more GFP expressed than by Ad only and DMPC-Ad, respectively). In conclusion, the efficiency of viral delivery and the stability of the virus were significantly enhanced when PLs containing apoA-I were used in cellular and zebrafish models.ope