자성 조절이 가능한 고분자-나노복합체를 이용한 미세 구조물의 제어

학위논문 (박사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2013. 8. 권성훈.In this dissertation, I introduce a new magnetic nanocomposite material system and in situ fabrication process that is not shape limited and allows the programming of heterogeneous magnetic anisotropy at the microscale. The key idea is to combine the self-assembling behavior of superparamagnetic nanoparticles, which have stronger magnetization than that of general paramagnetic materials, with a spatially modulated photopatterning process. By repetitively tuning the nanoparticle assembly and fixing the assembled state using photopolymerization, I fabricate microactuators for which all parts move in different directions under a homogeneous magnetic field. To show the feasibility of this concept, I demonstrate polymeric nanocomposite actuators capable of two dimensional and three-dimensional complex actuations that have rarely been achieved using conventional microactuators. This approach greatly simplifies the manufacturing process and also offers effective rules for designing novel and complex microcomponents using a nanocomposite material with engineered magnetic anisotropy. First, I investigate the self-assembling behavior of both ferromagnetic magnetite nanoparticles and superparamagnetic nanoparticles using Monte Carlo simulation. Magnetic materials used to fabricate magnetic polymer composite include ferrimagnetic magnetite nanoparticles with 50nm of averaged diameter and superparamagnetic magnetite nanoparticles with 280nm of averaged diameter. Magnetic particle interactions, that critically affect to the self-assembling behavior of the magnetic nanoparticles, such as particle-field interaction, particle-particle dipole interaction, magnetic anisotropy and steric layer repulsion are considered. I adopt cluster-moving Monte Carlo simulation method to analyze the magnetic self-assembly of magnetic nanoparticles and investigate the self-assembling behavior of the magnetite nanoparticles varying the intensity of the applied magnetic field during the chain formation and the concentration of the magnetic nanoparticles. The result shows that the well-defined magnetic chains are formed as both the intensity of the applied magnetic field and the magnetic nanoparticle concentration increase. Also, a novel method to fabricate magnetic nanoparticle embedded polymer composite microstructure is introduced. Briefly, the combination of photocurable polymer and magnetic nanoparticles is photopolymerized to immobilize the various states of magnetic nanoparticles. I especially adopt a system called optofluidic maskless lithography system to fabricate various shapes of polymeric microstructures within a second. Also, I develop a model system to describe the actuation of a magnetic polymer composite. The magnetic torque, the derivative of system energy, of the composite microstructure embedding magnetic chains is calculated based on the expanded Monte Carlo simulation result. And, the steady state elastic modulus of the magnetic composite microbeam is induced by utilizing the simulated torque and cantilever bending experiment result. The movement of cantilever type microstructure is investigated at equilibrium state that the magnetic torque equals to the mechanical restoring torque. As an application, I demonstrate multiaxial microactuators. Polymeric microcomponents are widely used in microelectromechanicalsystems (MEMS) and lab-on-a-chip devices, but they suffer from the lack of complex motion, effective addressability and precise shape control. To address these needs, I fabricated polymeric nanocomposite microactuators driven by programmable heterogeneous magnetic anisotropy. Spatially modulated photopatterning was applied in a shape independent manner to microactuator components by successive confinement of self-assembled magnetic nanoparticles in a fixed polymer matrix. By freely programming the rotational axis of each component, I demonstrate that the polymeric microactuators can undergo predesigned, complex two- and three dimensional motion. Finally I also introduce a novel color changing microactuators based on the self-assembling behavior of the magnetic nanoparticles. I propose a color-tunable microactuator utilizing the optical and magnetic behaviors of one-dimensionally assembled superparamagnetic nanoparticles that play the role of a one-dimensional Bragg reflector and establish a magnetic easy axis. By combining these properties with rapid photopolymerization, I developed red, blue, and green micropixels whose colors could be tuned by the application of an external magnetic field. This strategy offers very simple methods for the fabrication and operation of soft color tunable surfaces with high resolution.Abstract i Contents v List of Figures vii List of Tables xxi Chapter 1 Introduction 1 1.1 Polymer Nanocomposite 4 1.2 Magnetic Polymer Composite 7 1.3 Magnetic Self-assembly 11 1.4 Main Concept 15 Chapter 2 Magnetic Nanoparticle Self-assembly 18 2.1 Material Specification 19 2.1.1 Crystalline Structure of Magnetite 19 2.1.2 Synthesis of Superparamagnetic Nanoparticles 22 2.1.3 Magnetic Anisotropy of Magnetite Nanoparticles 23 2.2 Interacting Magnetic Nanoparticle with MC Simulation 27 2.2.1 Interaction Energy of Magnetic Nanoparticles 27 2.2.2 2D Cluster-moving Monte Carlo Simulation 31 2.3 Self-assembly of Magnetic Nanoparticles 34 2.3.1 Self-assembly of Ferrimagnetic Nanoparticles 36 2.3.2 Self-assembly of Superparamagnetic Nanoparticles 41 2.4 Conclusion 46 Chapter 3 Magnetic Nanoparticle Embedded Polymer Composite 47 3.1 Optofluidic Maskless Lithography 48 3.2 In-situ Fabrication Process 50 3.3 Torque on Magnetic Composite Structure 54 3.3.1 Magnetic Torque from Self-assembled Nanoparticles 54 3.3.2 Magnetic Torque on Arbitrary Structure 59 3.3.3 Elastic Modulus of Magnetic Composite Beam 61 3.4 Deisgn Principles 65 3.4.1 Simple Cantilever 66 3.5 Conclusion 70 Chapter 4 Multiaxial Microactuators 71 4.1 Fabrication 72 4.1.1 Various Types of Microfluidic Devices 74 4.1.2 Micropatterning of PDMS Thin Film on Glass Substrate 76 4.1.3 Grey Mask for Flexible Hinge 77 4.2 Microfluidic Components 79 4.3 Various Types of Multiaxial Microactuators 82 4.4 Rotating Microstructures 87 4.5 Microrobot 89 4.6 Conclusion 92 Chapter 5 Magnetochromatic Microactuators 93 5.1 Fabrication 94 5.2 Structural Color Generation 97 5.3 Color Change of Microsurface 100 5.4 Micropatterns 103 5.5 Conclusion 105 Conclusion and Future Work 106 Bibliography 109 국문 초록 119Docto

Design and optimization of magnetostrictive actuator

Magnetostnctive ("MS') technology and Magneto-Rheologlcal Fluid ("MRF") technology are old "newcomers" coming to the market at high speed. Various industries including the automotive industry are full of potential MS and MRF applications. Magnetostrictive technology and Magneto-Rheological Fluid technology have been successfully employed in some low and high volume applications A structure based on "MSm-technology might be the next generation in design for products where power density, accuracy and dynamic performance are key features. Since the introduction of active (MS) materials such as Terfenol-D, \nth stable characteristics over a wide range of temperatures and high magnetoelastic properties, interest in MS technology has been growing. Additionally, for products where is a need to control fluid motion by varying the viscosity, a structure based on MRF might be an improvement in performance. Two aspects of this technology, direct shear mode (used in brakes and clutches) and valve mode (used in dampers) have been studied thoroughly and several applications are already present on the market. Excellent features like fast response, slmple interface between electrical input and hydraulic output make MRF technology attractive for many applications. This dissertation is the introduction of an actuator based on "MS"-technology The possible control arrangement is based on "MR"-technology. The thesis is submitted for the degree of the PhD The dissertation contains the layout definition, analytical calculations, simulations, and design verification and optimization with evaluation of experimental results for the actuator based on "MS"-technology in combination of a possible control device based on "MR"-technology

Synthesis of gold nano-particles in a microfluidic platform for water quality monitoring applications

A microfluidic lab-on-a-chip (LOC) device for in-situ synthesis of gold nano-particles was developed. The long term goal is to develop a portable hand-held diagnostic platform for monitoring water quality (e.g., detecting metal ion pollutants). The LOC consists of micro-chambers housing different reagents and samples that feed to a common reaction chamber. The reaction products are delivered to several waste chambers in a pre-defined sequence to enable reagents/ samples to flow into and out of the reaction chamber. Passive flow actuation is obtained by capillary driven flow (wicking) and dissolvable microstructures called ‘salt pillars’. The LOC does not require any external power source for actuation and the passive microvalves enable flow actuation at predefined intervals. The LOC and the dissolvable microstructures are fabricated using a combination of photolithography and soft lithography techniques. Experiments were conducted to demonstrate the variation in the valve actuation time with respect to valve position and geometric parameters. Subsequently, analytical models were developed using one dimensional linear diffusion theory. The analytical models were in good agreement with the experimental data. The microvalves were developed using various salts: polyethylene glycol, sodium chloride and sodium acetate. Synthesized in-situ in our experiments, gold nano-particles exhibit specific colorimetric and optical properties due to the surface plasmon resonance effect. These stabilized mono-disperse gold nano-particles can be coated with bio-molecular recognition motifs on their surfaces. A colorimetric peptide assay was thus developed using the intrinsic property of noble metal nano-particles. The LOC device was further developed on a paper microfluidics platform. This platform was tested successfully for synthesis of gold nano-particles using a peptide assay and using passive salt-bridge microvalves. This study proves the feasibility of a LOC device that utilizes peptide assay for synthesis of gold nano-particles in-situ. It could be highly significant in a simple portable water quality monitoring platform

Microelectromechanical Systems and Devices

The advances of microelectromechanical systems (MEMS) and devices have been instrumental in the demonstration of new devices and applications, and even in the creation of new fields of research and development: bioMEMS, actuators, microfluidic devices, RF and optical MEMS. Experience indicates a need for MEMS book covering these materials as well as the most important process steps in bulk micro-machining and modeling. We are very pleased to present this book that contains 18 chapters, written by the experts in the field of MEMS. These chapters are groups into four broad sections of BioMEMS Devices, MEMS characterization and micromachining, RF and Optical MEMS, and MEMS based Actuators. The book starts with the emerging field of bioMEMS, including MEMS coil for retinal prostheses, DNA extraction by micro/bio-fluidics devices and acoustic biosensors. MEMS characterization, micromachining, macromodels, RF and Optical MEMS switches are discussed in next sections. The book concludes with the emphasis on MEMS based actuators

Hydrogel-based logic circuits for planar microfluidics and lab-on-a-chip automation

The transport of vital nutrient supply in fluids as well as the exchange of specific chemical signals from cell to cell has been optimized over billion years of natural evolution. This model from nature is a driving factor in the field of microfluidics, which investigates the manipulation of the smallest amounts of fluid with the aim of applying these effects in fluidic microsystems for technical solutions. Currently, microfluidic systems are receiving attention, especially in diagnostics, \textit{e.g.} as SARS-CoV-2 antigen tests, or in the field of high-throughput analysis, \textit{e.g.} for cancer research. Either simple-to-use or large-scale integrated microfluidic systems that perform biological and chemical laboratory investigations on a so called Lab-on-a-Chip (LoC) provide fast analysis, high functionality, outstanding reproducibility at low cost per sample, and small demand of reagents due to system miniaturization. Despite the great progress of different LoC technology platforms in the last 30 years, there is still a lack of standardized microfluidic components, as well as a high-performance, fully integrated on-chip automation. Quite promising for the microfluidic system design is the similarity of the Kirchhoff's laws from electronics to predict pressure and flow rate in microchannel structures. One specific LoC platform technology approach controls fluids by active polymers which respond to specific physical and chemical signals in the fluid. Analogue to (micro-)electronics, these active polymer materials can be realized by various photolithographic and micro patterning methods to generate functional elements at high scalability. The so called chemofluidic circuits have a high-functional potential and provide “real” on-chip automation, but are complex in system design. In this work, an advanced circuit concept for the planar microfluidic chip architecture, originating from the early era of the semiconductor-based resistor-transistor-logic (RTL) will be presented. Beginning with the state of the art of microfluidic technologies, materials, and methods of this work will be further described. Then the preferred fabrication technology is evaluated and various microfluidic components are discussed in function and design. The most important component to be characterized is the hydrogel-based chemical volume phase transition transistor (CVPT) which is the key to approach microfluidic logic gate operations. This circuit concept (CVPT-RTL) is robust and simple in design, feasible with common materials and manufacturing techniques. Finally, application scenarios for the CVPT-RTL concept are presented and further development recommendations are proposed.:1 The transistor: invention of the 20th century 2 Introduction to fluidic microsystems and the theoretical basics 2.1 Fluidic systems at the microscale 2.2 Overview of microfluidic chip fabrication 2.2.1 Common substrate materials for fluidic microsystems 2.2.2 Structuring polymer substrates for microfluidics 2.2.3 Polymer chip bonding technologies 2.3 Fundamentals and microfluidic transport processes 2.3.1 Fluid dynamics in miniaturized systems 2.3.2 Hagen-Poiseuille law: the fluidic resistance 2.3.3 Electronic and microfluidic circuit model analogy 2.3.4 Limits of the electro-fluidic analogy 2.4 Active components for microfluidic control 2.4.1 Fluid transport by integrated micropumps 2.4.2 Controlling fluids by on-chip microvalves 2.4.3 Hydrogel-based microvalve archetypes 2.5 LoC technologies: lost in translation? 2.6 Microfluidic platforms providing logic operations 2.6.1 Hybrids: MEMS-based logic concepts 2.6.2 Intrinsic logic operators for microfluidic circuits 2.7 Research objective: microfluidic hydrogel-based logic circuits 3 Stimuli-responsive polymers for microfluidics 3.1 Introduction to hydrogels 3.1.1 Application variety of hydrogels 3.1.2 Hydrogel microstructuring methods 3.2 Theory: stimuli-responsive hydrogels 3.3 PNIPAAm: a multi-responsive hydrogel 4 Design, production and characterization methods of hydrogel-based microfluidic systems 4.1 The semi-automated computer aided design approach for microfluidic systems 4.2 The applied design process 4.3 Fabrication of microfluidic chips 4.3.1 Photoresist master fabrication 4.3.2 Soft lithography for PDMS chip production 4.3.3 Assembling PDMS chips by plasma bonding 4.4 Integration of functional hydrogels in microfluidic chips 4.4.1 Preparation of a monomer solution for hydrogel synthesis 4.4.2 Integration methods 4.5 Effects on hydrogel photopolymerization and the role of integration method 4.5.1 Photopolymerization from monomer solutions: managing the diffusion of free radicals 4.5.2 Hydrogel adhesion and UV light intensity distribution in the polymerization chamber 4.5.3 Hydrogel shrinkage behavior of different adhesion types 4.6 Comparison of the integration methods 4.7 Characterization setups for hydrogel actuators and microfluidic measurements . 71 4.7.1 Optical characterization method to describe swelling behavior 4.7.2 Setup of a microfluidic test stand 4.8 Conclusion: design, production and characterization methods 5 VLSI technology for hydrogel-based microfluidics 5.1 Overview of photolithography methods 5.2 Standard UV photolithography system for microfluidic structures 5.3 Self-made UV lithography system suitable for the mVLSI 5.3.1 Lithography setup for the DFR and SU-8 master exposure 5.3.2 Comparison of mask-based UV induced crosslinking for DFR and SU-8 5.4 Mask-based UV photopolymerization for mVLSI hydrogel patterning 5.4.1 Lithography setup for the photopolymerization of hydrogels 5.4.2 Hydrogel photopolymerization: experiments and results 5.4.3 Troubleshooting: photopolymerization of hydrogels 5.5 Conclusion: mVLSI technologies for hydrogel-based LoCs 6 Components for chemofluidic circuit design 6.1 Passive components in microfluidics 6.1.1 Microfluidic resistor 6.1.2 Planar-passive microfluidic signal mixer 6.1.3 Phase separation: laminar flow signal splitter 6.1.4 Hydrogel-based microfluidic one-directional valves 6.2 Hydrogel-based active components 6.2.1 Reversible hydrogel-based valves 6.2.2 Hydrogel-based variable resistors 6.2.3 CVPT: the microfluidic transistor 6.3 Conclusion: components for chemofluidic circuits 7 Hydrogel-based logic circuits in planar microfluidics 7.1 Development of a planar CVPT logic concept 7.1.1 Challenges of planar microfluidics 7.1.2 Preparatory work and conceptional basis 7.2 The microfluidic CVPT-RTL concept 7.3 The CVPT-RTL NAND gate 7.3.1 Circuit optimization stabilizing the NAND operating mode 7.3.2 Role of laminar flow for the CVPT-RTL concept 7.3.3 Hydrogel-based components for improved switching reliability 7.4 One design fits all: the NOR, AND and OR gate 7.5 Control measures for cascaded systems 7.6 Application scenarios for the CVPT-RTL concept 7.6.1 Use case: automated cell growth system 7.6.2 Use case: chemofluidic converter 7.7 Conclusion: Hydrogel-based logic circuits 8 Summary and outlook 8.1 Scientific achievements 8.2 Summarized recommendations from this work Supplementary information SI.1 Swelling degree of BIS-pNIPAAm gels SI.2 Simulated ray tracing of UV lithography setup by WinLens® SI.3 Determination of the resolution using the intercept theorem SI.4 Microfluidic master mold test structures SI.4.1 Polymer and glass mask comparison SI.4.2 Resolution Siemens star in DFR SI.4.3 Resolution Siemens star in SU-8 SI.4.4 Integration test array 300 μm for DFR and SU-8 SI.4.5 Integration test array 100 μm for SU-8 SI.4.6 Microfluidic structure for different technology parameters SI.5 Microfluidic test setups SI.6 Supplementary information: microfluidic components SI.6.1 Compensation methods for flow stabilization in microfluidic chips SI.6.2 Planar-passive microfluidic signal mixer SI.6.3 Laminar flow signal splitter SI.6.4 Variable fluidic resistors: flow rate characteristics SI.6.5 CVPT flow rate characteristics for high Rout Standard operation proceduresDer Transport von lebenswichtigen Nährstoffen in Flüssigkeiten sowie der Austausch spezifischer chemischer Signale von Zelle zu Zelle wurde in Milliarden Jahren natürlicher Evolution optimiert. Dieses Vorbild aus der Natur ist ein treibender Faktor im Fachgebiet der Mikrofluidik, welches die Manipulation kleinster Flüssigkeitsmengen erforscht um diese Effekte in fluidischen Mikrosystemen für technische Lösungen zu nutzen. Derzeit finden mikrofluidische Systeme vor allem in der Diagnostik, z.B. wie SARS-CoV-2-Antigentests, oder im Bereich der Hochdurchsatzanalyse, z.B. in der Krebsforschung, besondere Beachtung. Entweder einfach zu bedienende oder hochintegrierte mikrofluidische Systeme, die biologische und chemische Laboruntersuchungen auf einem sogenannten Lab-on-a-Chip (LoC) durchführen, bieten schnelle Analysen, hohe Funktionalität, hervorragende Reproduzierbarkeit bei niedrigen Kosten pro Probe und einen geringen Bedarf an Reagenzien durch die Miniaturisierung des Systems. Trotz des großen Fortschritts verschiedener LoC-Technologieplattformen in den letzten 30 Jahren mangelt es noch an standardisierten mikrofluidischen Komponenten sowie an einer leistungsstarken, vollintegrierten On-Chip-Automatisierung. Vielversprechend für das Design mikrofluidischer Systeme ist die Ähnlichkeit der Kirchhoff'schen Gesetze aus der Elektronik zur Vorhersage von Druck und Flussrate in Mikrokanalstrukturen. Ein spezifischer Ansatz der LoC-Plattformtechnologie steuert Flüssigkeiten durch aktive Polymere, die auf spezifische physikalische und chemische Signale in der Flüssigkeit reagieren. Analog zur (Mikro-)Elektronik können diese aktiven Polymermaterialien durch verschiedene fotolithografische und mikrostrukturelle Methoden realisiert werden, um funktionelle Elemente mit hoher Skalierbarkeit zu erzeugen.\\ Die sogenannten chemofluidischen Schaltungen haben ein hohes funktionales Potenzial und ermöglichen eine 'wirkliche' on-chip Automatisierung, sind jedoch komplex im Systemdesign. In dieser Arbeit wird ein fortgeschrittenes Schaltungskonzept für eine planare mikrofluidische Chiparchitektur vorgestellt, das aus der frühen Ära der halbleiterbasierten Resistor-Transistor-Logik (RTL) hervorgeht. Beginnend mit dem Stand der Technik der mikrofluidischen Technologien, werden Materialien und Methoden dieser Arbeit näher beschrieben. Daraufhin wird die bevorzugte Herstellungstechnologie bewertet und verschiedene mikrofluidische Komponenten werden in Funktion und Design diskutiert. Die wichtigste Komponente, die es zu charakterisieren gilt, ist der auf Hydrogel basierende chemische Volumen-Phasenübergangstransistor (CVPT), der den Schlüssel zur Realisierung mikrofluidische Logikgatteroperationen darstellt. Dieses Schaltungskonzept (CVPT-RTL) ist robust und einfach im Design und kann mit gängigen Materialien und Fertigungstechniken realisiert werden. Zuletzt werden Anwendungsszenarien für das CVPT-RTL-Konzept vorgestellt und Empfehlungen für die fortlaufende Entwicklung angestellt.:1 The transistor: invention of the 20th century 2 Introduction to fluidic microsystems and the theoretical basics 2.1 Fluidic systems at the microscale 2.2 Overview of microfluidic chip fabrication 2.2.1 Common substrate materials for fluidic microsystems 2.2.2 Structuring polymer substrates for microfluidics 2.2.3 Polymer chip bonding technologies 2.3 Fundamentals and microfluidic transport processes 2.3.1 Fluid dynamics in miniaturized systems 2.3.2 Hagen-Poiseuille law: the fluidic resistance 2.3.3 Electronic and microfluidic circuit model analogy 2.3.4 Limits of the electro-fluidic analogy 2.4 Active components for microfluidic control 2.4.1 Fluid transport by integrated micropumps 2.4.2 Controlling fluids by on-chip microvalves 2.4.3 Hydrogel-based microvalve archetypes 2.5 LoC technologies: lost in translation? 2.6 Microfluidic platforms providing logic operations 2.6.1 Hybrids: MEMS-based logic concepts 2.6.2 Intrinsic logic operators for microfluidic circuits 2.7 Research objective: microfluidic hydrogel-based logic circuits 3 Stimuli-responsive polymers for microfluidics 3.1 Introduction to hydrogels 3.1.1 Application variety of hydrogels 3.1.2 Hydrogel microstructuring methods 3.2 Theory: stimuli-responsive hydrogels 3.3 PNIPAAm: a multi-responsive hydrogel 4 Design, production and characterization methods of hydrogel-based microfluidic systems 4.1 The semi-automated computer aided design approach for microfluidic systems 4.2 The applied design process 4.3 Fabrication of microfluidic chips 4.3.1 Photoresist master fabrication 4.3.2 Soft lithography for PDMS chip production 4.3.3 Assembling PDMS chips by plasma bonding 4.4 Integration of functional hydrogels in microfluidic chips 4.4.1 Preparation of a monomer solution for hydrogel synthesis 4.4.2 Integration methods 4.5 Effects on hydrogel photopolymerization and the role of integration method 4.5.1 Photopolymerization from monomer solutions: managing the diffusion of free radicals 4.5.2 Hydrogel adhesion and UV light intensity distribution in the polymerization chamber 4.5.3 Hydrogel shrinkage behavior of different adhesion types 4.6 Comparison of the integration methods 4.7 Characterization setups for hydrogel actuators and microfluidic measurements . 71 4.7.1 Optical characterization method to describe swelling behavior 4.7.2 Setup of a microfluidic test stand 4.8 Conclusion: design, production and characterization methods 5 VLSI technology for hydrogel-based microfluidics 5.1 Overview of photolithography methods 5.2 Standard UV photolithography system for microfluidic structures 5.3 Self-made UV lithography system suitable for the mVLSI 5.3.1 Lithography setup for the DFR and SU-8 master exposure 5.3.2 Comparison of mask-based UV induced crosslinking for DFR and SU-8 5.4 Mask-based UV photopolymerization for mVLSI hydrogel patterning 5.4.1 Lithography setup for the photopolymerization of hydrogels 5.4.2 Hydrogel photopolymerization: experiments and results 5.4.3 Troubleshooting: photopolymerization of hydrogels 5.5 Conclusion: mVLSI technologies for hydrogel-based LoCs 6 Components for chemofluidic circuit design 6.1 Passive components in microfluidics 6.1.1 Microfluidic resistor 6.1.2 Planar-passive microfluidic signal mixer 6.1.3 Phase separation: laminar flow signal splitter 6.1.4 Hydrogel-based microfluidic one-directional valves 6.2 Hydrogel-based active components 6.2.1 Reversible hydrogel-based valves 6.2.2 Hydrogel-based variable resistors 6.2.3 CVPT: the microfluidic transistor 6.3 Conclusion: components for chemofluidic circuits 7 Hydrogel-based logic circuits in planar microfluidics 7.1 Development of a planar CVPT logic concept 7.1.1 Challenges of planar microfluidics 7.1.2 Preparatory work and conceptional basis 7.2 The microfluidic CVPT-RTL concept 7.3 The CVPT-RTL NAND gate 7.3.1 Circuit optimization stabilizing the NAND operating mode 7.3.2 Role of laminar flow for the CVPT-RTL concept 7.3.3 Hydrogel-based components for improved switching reliability 7.4 One design fits all: the NOR, AND and OR gate 7.5 Control measures for cascaded systems 7.6 Application scenarios for the CVPT-RTL concept 7.6.1 Use case: automated cell growth system 7.6.2 Use case: chemofluidic converter 7.7 Conclusion: Hydrogel-based logic circuits 8 Summary and outlook 8.1 Scientific achievements 8.2 Summarized recommendations from this work Supplementary information SI.1 Swelling degree of BIS-pNIPAAm gels SI.2 Simulated ray tracing of UV lithography setup by WinLens® SI.3 Determination of the resolution using the intercept theorem SI.4 Microfluidic master mold test structures SI.4.1 Polymer and glass mask comparison SI.4.2 Resolution Siemens star in DFR SI.4.3 Resolution Siemens star in SU-8 SI.4.4 Integration test array 300 μm for DFR and SU-8 SI.4.5 Integration test array 100 μm for SU-8 SI.4.6 Microfluidic structure for different technology parameters SI.5 Microfluidic test setups SI.6 Supplementary information: microfluidic components SI.6.1 Compensation methods for flow stabilization in microfluidic chips SI.6.2 Planar-passive microfluidic signal mixer SI.6.3 Laminar flow signal splitter SI.6.4 Variable fluidic resistors: flow rate characteristics SI.6.5 CVPT flow rate characteristics for high Rout Standard operation procedure

The Design, Fabrication, and Magnetic Actuation of a Microactuator to Accomplish Propulsion and Large Deflection in Viscous and Elastic Environments

Biomimetics is the study of the structure and function of biological organisms, properties, or substances to inform or inspire the creation of artificial mimics. Nature's evolutionarily evolved answers to its own obstacles can become great solutions to our problems in the fields of physics, materials science, and engineering. The field of biomimetics has both led to technological advances and utilized biomimetic systems to glean knowledge about their biological inspirations. I have developed a single biomimetic system which both mimics a biological system well enough to inform biology and is capable of advancing technology. This biomimetic system is composed of novel core-shell microrods that closely mimic the size of biological cilia and generate fluid transport in both viscous and viscoelastic fluids. Complex biological processes such as the determination of left-right asymmetry in the vertebrate embryonic node and mucociliary clearance in the lung are dependent on the successful transport of fluids, both buffer-like and viscoelastic. A biomimetic system such as the one I have developed allows us to compare cilia-driven transport in both aqueous and viscoelastic fluids. In addition, I have used arrays of these core-shell microrods, comprising a flexible poly(dimethylsiloxane) core surrounded by a 100 nm shell of nickel, to assess the time evolution of fluid properties at the microscale, such as the formation of blood clots, which act to stem the flow of blood in the event of trauma or tissue damage. Using this system as an assay for the onset of clot development results in clinically relevant clotting time measurements. I will discuss these applications for the use of this biomimetic cilia system, as well as the system's design parameters and the fabrication procedure.Doctor of Philosoph

국소영역 집속이온빔 화학기상증착을 이용한 나노구조물 제작

학위논문 (박사)-- 서울대학교 대학원 : 공과대학 기계항공공학부, 2018. 2. 안성훈.In the time since focused ion beam-induced chemical vapor deposition (FIB-CVD) process was first introduced in the 1980s, it has become widely used not only for repair of semi-conductors, but also in the fabrication of various micro/nano structure devices including electronic components, sensors/actuators, and even nanomaterials. As the usability of the process increases, many researchers have studied the fundamentals of the process to improve process performances such as precision, efficiency, and purity of the deposited material. Despite these studies, however, due to the sensitive process parameters, and the complicated deposition mechanisms interacting with ions, electrons, precursor gases and a solid substrate, the fundamental mechanism of the process has not been yet clearly defined. The FIB-CVD process is a process in which some components of a precursor compound are deposited on the substrate by chemical reaction of the precursor gas. In general, temperature condition is an important factor in determining the chemical reaction rate. The temperature is inevitably one of the crucial process parameters. Previous studies on the effect of temperature on the process have been reported on the deposition characteristics according to the temperature of the precursor reservoir and the substrate temperature. However, even though the temperature of the precursor gas is directly related to the chemical reaction, little research on this has been done. This is mainly due to the fact that it is difficult to construct an experiment in which only the temperature of the precursor gas is used as a dependent variable at a gas injection system (GIS) responsible for supplying precursor gas. In this study, the effect of precursor gas temperature on FIB-CVD process was investigated from the viewpoint of deposition rate. In order to experimentally explore the influence of the gas temperature, a GIS which can independently control the precursor gas temperature was developed. With the developed GIS, the effect of the precursor gas temperature on the deposition rate of C14H10 precursor in FIB-CVD process was investigated. In addition, to theoretically understand the experimental results, a numerical model of the FIB-CVD deposition mechanism was developed. In order to solve the difficulties of the distance calculation between the deposition surface evolved in real time and the emitted electrons, which was difficult to consider in the conventional numerical methods, the Hausdorff distance concept generally used for object recognition in image processing was firstly adapted. Finally, the shape memory (SMA) based micro bending actuator was fabricated by modifying the deflection behavior of a SMA linear actuator with a localized carbon block deposited via FIB-CVD process using optimized precursor gas temperature.Chapter 1. Introduction 1 1.1 Technologies for micro/nanoscale structure prototyping 1 1.2 Focused ion beam induced chemical vapor deposition 2 1.3 Thesis motivation and framework 8 Chapter 2. System Integration 12 2.1 Development of a gas injection system (GIS) 12 2.1.1 Design 12 2.1.2 Evaluation 24 2.2 Experimental setup of FIB-CVD process 30 Chapter 3. Experiment 39 3.1 Preliminary experiment 39 3.2 Surface diffusion and precursor gas temperature 46 Chapter 4. Modeling and Simulation 53 4.1 Dynamics of precursor gas flow 56 4.2 Simulation of precursor gas transfer model 59 4.2.1 Parameter initialization 63 4.2.2 Discretization of simulated space 67 4.2.3 Implementation of simulation 68 4.2.4 Results of the precursor gas transfer simulation 71 4.3 Simulation of FIB-CVD process 73 4.3.1 Simulation overview 73 4.3.2 The trajectory of a primary ion 76 4.3.3 The trajectory of a secondary electron 84 4.3.4 Dynamics of precursor molecules on the surface of substrate 91 4.3.5 Cellular automata model for evolution of deposition 95 4.3.6 Hausdorff distance transformation 98 4.3.7 Simulation of FIB-CVD process 103 4.3.8 Results of the simulation 108 Chapter 5. Fabrication of micro-actuator 120 5.1 Introduction 120 5.2 Fabrication process of a micro-actuator 122 5.3 Deflection behavior of SMA carbon composite actuator 127 5.4 Mechanical analysis of the stiffness of the deposited carbon block 130 Chapter 6. Conclusions 139 Bibliography 141 국문 초록 149Docto