On-chip Magnetic 3D Soft Microactuators Made by Gray-scale Lithography

2008 IEEE/RSJ International Conference on Intelligent Robots and Systems, Acropolis Convention Center, Nice, France, Sept, 22-26, 200

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

Recent Advances on Nanocomposite Resists With Design Functionality for Lithographic Microfabrication

Nanocomposites formed by a phase-dispersed nanomaterial and a polymeric host matrix are highly attractive for nano- and micro-fabrication. The combination of nanoscale and bulk materials aims at achieving an effective interplay between extensive and intensive physical properties. Nanofillers display size-dependent effects, paving the way for the design of tunable functional composites. The matrix, on the other hand, can facilitate or even enhance the applicability of nanomaterials by allowing their easy processing for device manufacturing. In this article, we review the field of polymer-based nanocomposites acting as resist materials, i.e. being patternable through radiation-based lithographic methods. A comprehensive explanation of the synthesis of nanofillers, their functionalization and the physicochemical concepts behind the formulation of nanocomposites resists will be given. We will consider nanocomposites containing different types of fillers, such as metallic, magnetic, ceramic, luminescent and carbon-based nanomaterials. We will outline the role of nanofillers in modifying various properties of the polymer matrix, such as the mechanical strength, the refractive index and their performance during lithography. Also, we will discuss the lithographic techniques employed for transferring 2D patterns and 3D shapes with high spatial resolution. The capabilities of nanocomposites to act as structural and functional materials in novel devices and selected applications in photonics, electronics, magnetism and bioscience will be presented. Finally, we will conclude with a discussion of the current trends in this field and perspectives for its development in the near future.Fil: Martínez, Eduardo David. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia - Nodo Bariloche | Comision Nacional de Energia Atomica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia - Nodo Bariloche.; ArgentinaFil: Prado, A.. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia - Nodo Bariloche | Comision Nacional de Energia Atomica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia - Nodo Bariloche.; ArgentinaFil: Gonzalez, M.. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia - Nodo Bariloche | Comision Nacional de Energia Atomica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia - Nodo Bariloche.; ArgentinaFil: Anguiano, S.. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia - Nodo Bariloche | Comision Nacional de Energia Atomica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia - Nodo Bariloche.; ArgentinaFil: Tosi, Leandro. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia - Nodo Bariloche | Comision Nacional de Energia Atomica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia - Nodo Bariloche.; ArgentinaFil: Salazar Alarcón, Leonardo. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia - Nodo Bariloche | Comision Nacional de Energia Atomica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia - Nodo Bariloche.; ArgentinaFil: Pastoriza, Hernan. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia - Nodo Bariloche | Comision Nacional de Energia Atomica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia - Nodo Bariloche.; Argentin

Fabrication of Polymer and Nanocomposite Microstructures and Microactuators by Capillary Infiltration and Replica Molding.

Addition of micro- and/or nanoscale textures to surfaces can enable engineering of a wide range of properties. Passive surfaces (using fixed microstructures) can manipulate cell adhesion, liquid drag, and thermal and electrical contact resistance. Active surfaces (using shape-changing microstructures) can enable modulation of liquid wetting, adhesion, and optical properties. Nevertheless, it remains a challenge to fabricate the mechanically and environmentally robust microstructures and microactuators in large arrays. This thesis presents new fabrication methods for microstructured polymer and nanocomposite surfaces. Two approaches are pursued: capillary driven infiltration of fabricated carbon nanotube (CNT) microstructures and replica molding (REM) of master templates in liquid crystal networks (LCNs). First, it is demonstrated that CNT-polymer microstructures can function as robust large-area master molds. The fabricated microstructures include pins, tubes, re-entrant microwells, bent pillars, and high-aspect-ratio honeycombs (thickness of 400nm, aspect ratio 50:1). All are used as master structures for replica molding. A 25-fold replication sequence is shown with no physical degradation of the master or the replicas. Further, the increased stiffness and toughness of CNT-SU-8 microstructures is quantified. Second, active surfaces were created by capillary infiltration of paraffin into CNT forests. Large stroke sheet actuators, exhibiting up to 20% thermal strain at 175°C are shown. Third, thermally and optically active LCN microstructure replicas were created. Their generated strains were measured to be 6% and 0.25%, respectively. In situ monitoring of the LCN phase and order was also performed. Although having low strains, optically active microstructures are attractive for future work because they can be actuated individually and remotely. These scalable methods of fabricating microstructured surfaces, both with robust mechanical properties and active geometries, indicate promise for enhancement of liquid wetting, adhesion, optical properties, and thermal conductivity of surfaces and interfaces. However, further increases in the thermally and optically generated strains are needed to make useful active surfaces. This could be accomplished by either material reformulation, improvements in material processing, or strain amplification via design of microstructure geometry.PhDMechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/102390/1/copicd_1.pd

4D Microprinting Based on Liquid Crystalline Elastomers

Two-photon laser printing (2PLP) is a disruptive three-dimensional (3D) printing technique that can afford structural fabrication at the submicrometer scale. Apart from constructing static 3D structures, research in fabricating dynamic ones, known as "4D printing”, is becoming a burgeoning field. 4D printed structures exhibit adaptability or tunability towards their environment through the control of an external stimulus. In contrast to the rapid growth in macroscale fabrication, progress in microprinted actuators has only been scarcely reported. Liquid crystal elastomer (LCE) stands out among the promising classes of smart materials for fabricating microrobotics or microactuators due to its distinct anisotropic property, which enables the printed structures to exhibit automated reversible movements upon exposure to stimuli without environmental limitations. Nevertheless, the use of 2PLP for the manufacture of 4D printed LCE microstructures with high versatility and complexity have presented some challenges, limiting their implementation in final applications. This thesis aims to overcome two main obstacles faced in this regard: first, the limitation of two-photon printable stimuli-responsive materials; and second, the lack of a facile approach for aligning liquid crystal (LC) within three dimensions. The first part of this thesis aims on expanding the library of materials used for implementing light responsiveness into LC microstructures, as light provides a higher degree of temporal and spatial control compared to other stimuli. The initial approach has involved incorporation of acrylate-functionalized photoresponsive molecules, such as azobenzene and the donor-acceptor Stenhouse adduct (DASA), into a LC ink using a conventional synthetic method. However, several challenges, such as compatibility with the LC ink, have prevented the achievement of 4D printing via 2PLP. The second approach is based on post-modifying printed LC structures and successfully fabricated microactuators with five different photoresponsive features by individually incorporating each light-absorbing molecule. Furthermore, LC microactuators that exhibit distinct actuation patterns under different colors of light were fabricated by simultaneously implementing orthogonal photoresponsive molecules. The second project presented in this thesis focuses on developing a new strategy to induce alignment domains in a more flexible manner, with the aim of spatially tailoring the LC topology of the 3D printed microstructures. This is achieved by microprinting 3D scaffolds based on polydimethylsiloxane (PDMS) to manipulate the alignment directions of LC molecules. Taking advantage of 2PLP to fabricate arbitrary scaffolds, LC alignments, including planar and radial patterns, could be introduced freely and simultaneously in three-dimensional space with varying degrees of complexity. The applicability of this alignment approach was demonstrated by fabricating responsive LC microstructures within different PDMS environments, and distinct actuation patterns were observed. Overall, these two breakthroughs have unveiled a wide array of new potentials for the utilization of responsive LC microsystems with tunable functionalities and customizable actuation responses, that can be applied across various domains and applications

FABRICATION OF MAGNETIC TWO-DIMENSIONAL AND THREE-DIMENSIONAL MICROSTRUCTURES FOR MICROFLUIDICS AND MICROROBOTICS APPLICATIONS

Micro-electro-mechanical systems (MEMS) technology has had an increasing impact on industry and our society. A wide range of MEMS devices are used in every aspects of our life, from microaccelerators and microgyroscopes to microscale drug-delivery systems. The increasing complexity of microsystems demands diverse microfabrication methods and actuation strategies to realize. Currently, it is challenging for existing microfabrication methods—particularly 3D microfabrication methods—to integrate multiple materials into the same component. This is a particular challenge for some applications, such as microrobotics and microfluidics, where integration of magnetically-responsive materials would be beneficial, because it enables contact-free actuation. In addition, most existing microfabrication methods can only fabricate flat, layered geometries; the few that can fabricate real 3D microstructures are not cost efficient and cannot realize mass production. This dissertation explores two solutions to these microfabrication problems: first, a method for integrating magnetically responsive regions into microstructures using photolithography, and second, a method for creating three-dimensional freestanding microstructures using a modified micromolding technique. The first method is a facile method of producing inexpensive freestanding photopatternable polymer micromagnets composed NdFeB microparticles dispersed in SU-8 photoresist. The microfabrication process is capable of fabricating polymer micromagnets with 3 µm feature resolution and greater than 10:1 aspect ratio. This method was used to demonstrate the creation of freestanding microrobots with an encapsulated magnetic core. A magnetic control system was developed and the magnetic microrobots were moved along a desired path at an average speed of 1.7 mm/s in a fluid environment under the presence of external magnetic field. A microfabrication process using aligned mask micromolding and soft lithography was also developed for creating freestanding microstructures with true 3D geometry. Characterization of this method and resolution limits were demonstrated. The combination of these two microfabrication methods has great potential for integrating several material types into one microstructure for a variety of applications

마이크로미터 이하 패턴 제작을 위한 디지털 포토리소그래피 기술

학위논문(박사) -- 서울대학교대학원 : 자연과학대학 물리학과, 2021.8. 권여리.Digital photolithography based on digital micromirror device (DMD) is considered the next-generation low-cost lithographic technology. However, DMD-based digital photolithography has been implemented only for micrometer-scale pattern generation, whereas sophisticated photonic devices require feature sizes of submicron. In this thesis, we adopt a high-magnification imaging optical system for a custom-built digital photolithography system to generate submicron-scale patterns. We propose techniques to enhance the versatility of the digital photolithography, pattern tilting and grayscale exposure. We demonstrate that photonic crystal band-edge lasers of various lattice structures and periods can be quality-assessment testbeds. We also tried to enhance pattern uniformity. The experimentally determined pixel spread function predicted the exposure result well, which means that we can improve the pattern quality through preliminary correction.디지털 미세거울 장치에 기반한 디지털 포토리소그래피는 차세대 저비용 리소그래피 기술로 여겨진다. 그러나 디지털 미세거울 장치 기반 디지털 포토리소그래피는 주기가 1 마이크론 이상인 패턴 제작시에만 사용되었다. 광자결정레이저 등의 광소자 제작을 위해서는 패턴의 주기가 수백나노미터 수준이어야 하는데, 아직 디지털 포토리소그래피로 이러한 광소자를 제작한 사례는 없었다. 회절 한계를 계산해 보았을 때, 1 마이크론 이하 주기의 패턴 제작이 충분히 가능할 것으로 판단되어, 고배율 결상광학계를 활용하여 디지털 포토리소그래피 시스템을 구축하였다. 구축된 시스템을 사용하여 감광액이 코팅된 시편에 노광을 진행하였으며, 1 마이크론 이하 주기의 패턴 제작이 가능함을 보였다. 마이크로미터 이하 주기의 패턴을 제작할 때, 디지털 포토리소그래피의 패턴 설계 자유도를 향상시키기 위한 두 가지 방법인 패턴 기울임, 회색조 노광을 제안하였으며 실험적으로 시연하였다. 디지털 리소그래피 시스템의 검증에는 광자결정 띠 가장자리 레이저가 주로 사용되었는데, 레이저 발진 여부를 통해 노광 패턴의 품질을 파악할 수 있고 레이저 파장을 통해 노광 패턴의 주기를 파악할 수 있기 때문이다. 또한 픽셀 분산 함수를 도입하여 이미지의 회절 계산 및 패턴 품질 향상을 위한 밝기 보정을 제안하였다. 보정에 의해 패턴의 품질이 크게 향상되어, 전자빔 리소그래피로 제작한 것과 비교할 수 있는 수준이 되었다.Chapter1 Introduction 1 1.1. Photonic crystals 1 1.1.1. Introduction 1 1.1.2. Photonic crystal band-edge laser 4 1.1.3. Photonic crystal cavity laser 6 1.2. Conventional lithography techniques 8 1.3. Alternative lithography technique: digital photolithography 10 1.4. Outline of the manuscript 12 Chapter2 Submicron-scale digital photolithography 14 2.1. Introduction 14 2.1.1. Schematic of digital photolithography system 14 2.1.2. Proposed digital photolithography system 16 2.1.3. Pixel pitch at image plane 17 2.1.4. Resolving power of proposed digital photolithography system 19 2.2. Fabrication process of air-bridge photonic crystal 21 2.3. Square-lattice photonic crystal laser device 22 Chapter3 Fine-tuning the lattice constant: pattern tilting 26 3.1. Introduction 26 3.1.1. Wavelength division multiplexing application 26 3.1.2. Pattern tilting 28 3.1.3. All possible tilting configurations 30 3.2. Result and discussion 31 3.2.1. Tilting square-lattice 31 3.2.2. Tilting hexagonal-lattice 33 Chapter4 Fine structural tuning: grayscale exposure 36 4.1. Introduction 36 4.1.1. Implementation of gray pixel 36 4.2. Result and discussion 38 4.2.1. Grayscale exposed squre-lattice 38 4.2.2. Grayscale exposed hexagonal-lattice 41 Chapter5 Enhancing pattern uniformity 42 5.1. Introduction 42 5.1.1. Airy disk point spread function 42 5.1.2. Broadening factor and exposure dose profile 47 5.1.3. Experimental determination of broadening factor 49 5.2. Result and discussion 51 5.2.1. Diffraction simulation based on pixel spread function 51 5.2.2. Correction strategy 56 5.2.3. Analysis of correction result 58 Chapter6 Conclusion and perspective 61 References 63 Abstract in Korean 70박

4D Printing at the Microscale

3D printing of adaptive and dynamic structures, also known as 4D printing, is one of the key challenges in contemporary materials science. The additional dimension refers to the ability of 3D printed structures to change their properties—for example, shape—over time in a controlled fashion as the result of external stimulation. Within the last years, significant efforts have been undertaken in the development of new responsive materials for printing at the macroscale. However, 4D printing at the microscale is still in its early stages. Thus, this progress report will focus on emerging materials for 4D printing at the microscale as well as their challenges and potential applications. Hydrogels and liquid crystalline and composite materials have been identified as the main classes of materials representing the state of the art of the growing field. For each type of material, the challenges and critical barriers in the material design and their performance in 4D microprinting are discussed. Importantly, further necessary strategies are proposed to overcome the limitations of the current approaches and move toward their application in fields such as biomedicine, microrobotics, or optics

Cantilever beam microactuators with electrothermal and electrostatic drive

Microfabrication provides a powerful tool for batch processing and miniaturization of mechanical systems into dimensional domain not accessible easily by conventional machining. CMOS IC process compatible design is definitely a big plus because of tremendous know-how in IC technologies, commercially available standard IC processes for a reasonable price, and future integration of microma-chined mechanical systems and integrated circuits. Magnetically, electrostatically and thermally driven microactuators have been reported previously. These actuators have applications in many fields from optics to robotics and biomedical engineering. At NJIT cleanroom, mono or multimorph microactuators have been fabricated using CMOS compatible process. In design and fabrication of these microactuators, internal stress due to thermal expansion coefficient mismatch and residual stress have been considered, and the microactuators are driven with electro-thermal power combined with electrostatical excitation. They can provide large force, and in- or out-of-plane actuation. In this work, an analytical model is proposed to describe the thermal actuation of in-plane (inchworm) actuators. Stress gradient throughout the thickness of monomorph layers is modeled as linearly temperature dependent Δσ. The nonlinear behaviour of out-of-plane actuators under electrothermal and electrostatic excitations is investigated. The analytical results are compared with the numerical results based on Finite Element Analysis. ANSYS, a general purpose FEM package, and IntelliCAD, a FEA CAD tool specifically designed for MEMS have been used extensively. The experimental results accompany each analytical and numerical work. Micromechanical world is three dimensional and 2D world of IC processes sets a limit to it. A new micromachining technology, reshaping, has been introduced to realize 3D structures and actuators. This new 3D fabrication technology makes use of the advantages of IC fabrication technologies and combines them with the third dimension of the mechanical world. Polycrystalline silicon microactuators have been reshaped by Joule heating. The first systematic investigation of reshaping has been presented. A micromirror utilizing two reshaped actuators have been designed, fabricated and characterized

Polymer NdFeB Hard Magnetic Scanner for Biomedical Scanning Applications

Micromirror scanners are the most significant of the micro-optical actuator elements with applications in portable digital displays, automotive head-up displays, barcode scanners, optical switches and scanning optical devices in the health care arena for external scanning diagnostics and in vivo scanning diagnostics. Recent development in microscanning technology has seen a shift from conventional electrostatic actuation to electromagnetic actuation mechanisms with major advantages in the ability to produce large scan angles with low voltages, remote actuation, the absence of the pull-in failure mode and the acceptable electrical safety compared to their electrostatic counterparts. Although attempts have been made to employ silicon substrate based MEMS deposition techniques for magnetic materials, the quality and performance of the magnets are poor compared to commercial magnets. In this project, we have developed novel low-cost single and dual-axis polymer hard magnetic micromirror scanners with large scan angles and low power consumption by employing the hybrid fabrication technique of squeegee coating to combine the flexibility of polydimethylsiloxane (PDMS) and the superior magnetic performance of fine particle isotropic NdFeB micropowders. PCB coils produce the Lorentz force required to actuate the mirror for scanning applications. The problem of high surface roughness, low radius of curvature and the magnetic field interaction between the gimbal frame and the mirror have been solved by a part PDMS-part composite fabrication process. Optimum magnetic, electrical and time dependent parameters have been characterized for the high performance operating conditions of the micromirror scanner. The experimental results have been demonstrated to verify the large scan angle actuation of the micromirror scanners at low power consumption