Thermo mechanical and Control Behaviour of Copper based Shape Memory Alloy Bimorph Actuator towards the Development of Micro Positioning System

A shape memory alloy (SMA) bimorph actuator is a composite structure composed of flexible polyimide substrate and SMA thin film deposited using thermal evaporation technique. In this work, the substrate thickness in the range of 25 - 75 mm was selected for the development of CuAlNiMn SMA bimorph actuator. An investigation on the control behavior of copper based SMA bimorph towards the development of micro positioning system has been performed. The actuation behavior of the SMA bimorph was studied using electrical actuation. Subsequently, a proportional integral derivative (PID) controller was designed to control the bimorph actuator with proper tuning of gain parameters. The displacement of the bimorph actuator was controlled through dedicated experimental setup consisted of laser displacement sensor, data acquisition system and LabVIEW software. The CuAlNiMn SMA bimorph actuator resulted in a satisfying control performance which can be extended to MEMS applications. A preliminary prototype of the SMA bimorph actuator based micro positioning system has been developed

형상기억 합금을 이용한 마이크로스케일 고속 구동기의 제작 및 평가

학위논문 (박사)-- 서울대학교 대학원 공과대학 기계항공공학부, 2017. 8. 안성훈.We designed, fabricated, and evaluated a shape memory alloy-based microscale actuator. To achieve complex shape fabrication and an in situ mechanical characterization, a manipulation and characterization platform equipped with high-resolution nanopositioners (with multiple degrees of freedom) and a micro-force sensor was developed. The challenges inherent in precise and accurate fabrication of samples with complex geometry were overcome so that the platform can be used for mechanical property characterization with an in situ method in the high vacuum chamber of a focused ion beam (FIB) system. Using the developed platform, diamond-shaped frame structures 1–1.5 μm in thickness were manufactured using an FIB milling process with a shape memory alloy (SMA). The behavior of these structures under mechanical deformation and changes in thermal conditions was investigated with respect to use as a driving force for a high-speed microscale actuator. Thermal energy was delivered by an optical method, including ion beam irradiation and laser irradiation. Because this method does not require any wiring, unlike other heating methods such as Joule heating, we could realize the fabricated SMA structure without any structural interruptions that could negatively affect the fast actuation motion. As an application, a microscale actuator is proposed. Due to the scale effect, a microscale linear motion actuator can vibrate at over 500 Hz with laser-induced heating. The reaction force and response speed were investigated according to changes in the laser switching speed and power. Additionally, a gripper having a negative Poissons ratio structure could grab small objects and deliver an objective by triggering the shape memory effect. We expect the proposed actuators to contribute to the development of micro- and nanoscale devices for microscale investigations and medical purposes.Chapter 1. Introduction 1.1. Toward miniaturization 1.2. Shape Memory Alloy (SMA) 1.3. Shape memory alloy based microscale actuator 1.4. Focused Ion Beam technique in micro- and nanoscale structuring 1.5. In-situ characterization in SEM/FIB system 1.6. Goals of this research Chapter 2. Platform for manufacturing and test 2.1. Focused Ion Beam (FIB) system 2.2. Platform design of in-situ fabrication and evaluation 2.3. Application of developed platform: Case studies Chapter 3. Fabrication and evaluation of SMA microstructure 3.1. Test platform 3.2. Thin film fabrication using FIB milling. 3.3. Patterning method in FIB milling process 3.4. Prediction of damages at the surface caused by FIB milling process 3.5. Characterization of SMA cells 3.6. Force depend on angle 3.7. Investigation of deformation behavior with computational simulation Chapter 4. Development of SMA based actuator. 4.1. Evaluation of shape memory effect. 4.2. Shape memory effect under ion beam irradiation condition 4.3. Shape memory effect under ambient heating 4.4. Shape memory effect with laser induced heating 4.5. Development of hardware for laser-induced SMA actuation Chapter 5. Development of high-speed micro-actuator and robot 5.1. High-speed linear actuation 5.2. Design and fabrication of Micro Gripper 5.3. High-speed linear vibration actuator 5.4. Actuation with 2-way shape memory effect Chapter 6. ConclusionsDocto

Thermomechanische Modellierung von Formgedächtnislegierung-basierten Mikroaktuatoren

Modeling finite deformation inelasticity often involves an incompressibility constraint on the inelastic stretches, which arises from physical considerations. Regularly, this constraint is fulfilled by use of the exponential map as a geometric integrator for the evolution equations. However, in this dissertation, a new geometric integrator for the unimodularity constraint is developed and analyzed. It builds on the work of Hurtado et al. from 2014, where this projection scheme was introduced for crystal plasticity. However, to make use of this projection scheme efficiently in a finite element context, additional numerical problems have to be overcome. The work at hand aims to contribute to this aim and extend existing works for shape memory alloys. It comprises of three publications of the author and his co-authors concentrating on the modeling of materials with an incompressibility constraint. The overall goal is to implement an efficient shape memory alloy model for the simulation of cooperative bistable shape memory nanoactuators.Die Modellierung von Inelastizität unter finiten Deformationen beinhaltet häufig eine Inkompressibilitätsbeschränkung für die inelastischen Dehnungen, welche sich aus physikalischen Überlegungen ergibt. In der Regel wird diese Bedingung durch die Verwendung der Exponentialabbildung als geometrischer Integrator für die Evolutionsgleichungen exakt erfüllt. In dieser Dissertation wird jedoch ein neuer geometrischer Integrator für die Unimodularitätsbeschränkung entwickelt und analysiert. Er baut auf der Arbeit von Hurtado et al. aus dem Jahr 2014 auf, wo dieses Projektionsschema für die Kristallplastizität eingeführt wurde. Um dieses Projektionsschema in einem Finite-Elemente-Kontext effizient nutzen zu können, müssen jedoch zusätzliche numerische Probleme überwunden werden.Die vorliegende Arbeit soll dazu beitragen und bestehende Arbeiten für Formgedächtnislegierungen erweitern. Sie ist ein Zusammenschluss von drei Publikationen des Autors und seiner Mitautoren, die sich auf die Modellierung von Materialien mit einer Inkompressibilitätsbeschränkung konzentrieren. Das übergeordnete Ziel ist es, ein effizientes Modell für Formgedächtnislegierungen zur Simulation von kooperativen bistabilen Formgedächtnis-Nanoaktuatoren zu implementieren

Development of Microactuators Based on the Magnetic Shape Memory Effect

The giant magneto-strain effect in Ni-Mn-Ga alloys is particularly attractive for actuator applications. Two different approaches are being pursued to develop MSM microactuators. To observe large deflections of Ni-Mn-Ga microactuators, the material should be exhibiting low twinning stress and large magnetic anisotropy. In addition, design rules and boundary conditions for operating the Ni-Mn-Ga actuator material are having significant importance for evolution of performance characteristics

형상기억합금 기반의 변형가능한 어그제틱 플라즈모닉 메타물질

학위논문 (석사) -- 서울대학교 대학원 : 공과대학 기계공학부, 2020. 8. 안성훈.금속 나노구조체의 표면 플라즈몬 공명은 독특한 전자기 특성으로인해 지금까지 꾸준한 관심을 끌고있다. 특히, 입사광의 파장보다 작은 크기의 전도성 나노 입자, 나노 구조체로 빛이 입사할 때 발생하는 국소 표면 플라즈몬 공명은 파장 흡수기, 색 필터 및 센서 등에 적용돼 왔다. 이는 공진 주파수가 나노 구조체의 크기, 형상 또는 주위의 유전체 특성에 따라 달리 결정되기 때문이다. 그러나, 이전까지의 연구에서 개발된 플라즈모닉 물질들은 고정된 구조에서 벗어나지 못해 공진 주파수를 연속적으로 변경시킬 수 없다는 한계를 가지고 있다. 이 문제는 플라즈모닉 메타물질의 실제적 적용에 어려움을 주었다. 이번 연구에서는, 가시광 영역에서 공명 주파수를 이동시킬 수 있는 어그제틱 나노 패턴이 새겨진 플라즈모닉 메타물질이 개발되었다. 이 메타물질은 직경이 25 µm인 형상기억합금 와이어로 제작되어 패턴이 인장되고 열에 의해 복원될 수 있다. 이러한 메타물질을 제작을 위해서 집속이온 빔을 이용하여 1 µm 두께의 형상기억합금 필름을 제작했고, 뛰어난 기계적 물성을 가진 어그제틱 패턴을 그 위에 새겼다. 이후, 이온 코터 스퍼터링과 전자빔 증착방식을 사용하여 패턴위에 금과 은 나노입자를 증착하였다. 패턴의 인장을 위해서는 마이크로 그리퍼를 사용하였으며, 인장 후 355 nm 레이저를 이용하여 패턴을 원래의 형상으로 되돌릴 수 있었다. 패턴 크기의 변화에 따른 반사 효과를 확인하기 위해, 우리는 스펙트로미터를 이용한 흡수픽을 측정했을 뿐만 아니라, 광학현미경을 통해 직접 색을 확인했다. 또한, finite difference time domain (FDTD) 방식을 이용하여 동일한 모델에 대해 반사율을 계산했고 그 결과를 실험결과와 비교했다. 위와 같은 실험을 통해, 먼저 여러가지 패턴의 크기에 따라 다양한 색이 나타나는 것을 확인했다. 또한 패턴을 잡아당겨 그 크기를 약 10% 까지 늘렸을 때, 흡수픽이 이동하고 반사색이 변화하는 것을 확인했다. 최종적으로, 형상기억효과를 이용하여 원래의 패턴크기로 되돌림으로서 변형가능한 어그제틱 플라즈모닉 메타물질을 증명했다.Surface plasmon resonance of metallic nanostructures has attracted steady attention for their distinct electromagnetic properties. In particular, localized surface plasmon resonance (LSPR) occurs when light enters conductive nanostructures or nanoparticles smaller than the incident wavelength has been applied to wave absorbers, color filters, and sensors. This is because the resonant frequency can be determined depending on the size, geometry, and dielectric environment of the structures. However, the plasmonic materials developed in the previous researches have a limitation that the resonant frequency could not be changed continuously due to their stationary structure. This problem makes it difficult for practical applications.  In this research, we develop plasmonic metamaterials with auxetic nano patterns that can shift the resonant frequency in the visible region. Shape memory alloy (SMA) wire with 25 µm diameter is used to stretch the patterns and bring them back. Using focused ion beam (FIB), 1 µm thick SMA thin film is fabricated from wire, and the auxetic nano patterns showing remarkable mechanical property are engraved on the film. Gold and silver nanoparticles are sputtered onto the patterned thin film using an ion coater sputtering and e-beam evaporation. We use a micro-gripper to stretch the patterns, and patterns are returned to its original shape by 355 nm laser. To confirm the effect of changing the size of patterns, we not only measure the absorption peak through the spectrometer but also observe the color directly through the microscope. Besides, the finite difference time domain (FDTD) method is used to calculate the reflectance and compare with the experimental results. Through the above experiment, it is confirmed that various colors appeared depending on the size of auxetic patterns. Also, when the pattern is pulled to increase the size to about 10%, it is measured that the absorption peak moved and the reflection color changed. By returning to the original pattern size using the shape memory effect, deformable auxetic plasmonic metamaterials are demonstrated.Chapter 1. Introduction 1 Chapter 2. Background 3 2.1. Localized surface plasmon resonance 3 2.2. Applications of localized surface plasmon resonance 4 2.3. Comparison with other principles 7 Chapter 3. Design, fabrication process, experimental setup 11 3.1. Design of auxetic pattern 12 3.2. Fabrication process 16 3.3. Experimental setup 19 Chapter 4. Localized surface plasmon resonance depending on the auxetic pattern size 21 4.1. The influence of Ag film in LSPR 22 4.2. Reflectance depending on the pattern size with Ag film 24 4.3. Reflectance depending on the pattern size with Au film 29 Chapter 5. Localized surface plasmon resonance of pattern under tension loading 31 5.1. Reflectance change of pattern under tension loading 33 5.2. Applications of deformable metamaterials 36 Chapter 6. Conclusions 38 References 40Maste

Temperature Homogenization of Co-Integrated Shape Memory—Silicon Bimorph Actuators

The high work density and beneficial downscaling of shape memory alloy (SMA) actuation performance provide a basis for the development of actuators and systems at microscales. Here, we report a novel monolithic fabrication approach for the co-integration of SMA and Si microstructures to enable SMA-Si bimorph microactuation. Double-beam cantilevers are chosen for the actuator layout to enable electrothermal actuation by Joule heating. The SMA materials under investigation are NiMnGa and NiTi(Hf) films with tunable phase transformation temperatures. We show that Joule heating of the cantilevers generates increasing temperature gradients for decreasing cantilever size, which hampers actuation performance. In order to cope with this problem, a new method for design optimization is presented based on finite element modeling (FEM) simulations. We demonstrate that temperature homogenization can be achieved by the design of additional folded beams in the perpendicular direction to the active beam cantilevers. Thereby, power consumption can be reduced by more than 35 % and maximum deflection can be increased up to a factor of 2 depending on the cantilever geometry

The Performance Evaluation of SMA Spring as Actuator for Gripping Manipulation

This paper is to present the evaluation of a TiNi Shape Memory Alloy (SMA) spring as actuator for the gripping manipulation. The SMA spring employed was a TiNi tensile spring which has a diameter of 50 mm wire and 350 gram hanging mass. The gripper fabricated consists of two fingers and each finger is actuated by the SMA spring. The total angular displacement of the gripper is 300. The power consumptions, the movements and force generations experimentations have been conducted. The DC signal and PWM signal with 12, 12Hz, 25Hz, 125Hz, 250Hz and the 1150Hz have been employed for driving the SMA. The experimental results indicated that the 125Hz of PWM signal was likely to be had a better performance than the other signals. The 125Hz PWM signal generated faster movement, lower power consumption, and constant rate of force. In this study, closed-loop control for gripping manipulation was also conducted. The close loop controller used is PID controller. The Ziegler-Nichols method has been used to predict the optimal gain of the controller, but the best performance was determined by experimentally tuning of the gains. The experimental results indicated that the PID controller is likely to be reliable controller for gripping manipulation of the SMA spring. To obtain the better performance, it is important to consider the SMA cooling responses and the long time of retain in certain position of the gripper

A Review of Smart Materials in Tactile Actuators for Information Delivery

As the largest organ in the human body, the skin provides the important sensory channel for humans to receive external stimulations based on touch. By the information perceived through touch, people can feel and guess the properties of objects, like weight, temperature, textures, and motion, etc. In fact, those properties are nerve stimuli to our brain received by different kinds of receptors in the skin. Mechanical, electrical, and thermal stimuli can stimulate these receptors and cause different information to be conveyed through the nerves. Technologies for actuators to provide mechanical, electrical or thermal stimuli have been developed. These include static or vibrational actuation, electrostatic stimulation, focused ultrasound, and more. Smart materials, such as piezoelectric materials, carbon nanotubes, and shape memory alloys, play important roles in providing actuation for tactile sensation. This paper aims to review the background biological knowledge of human tactile sensing, to give an understanding of how we sense and interact with the world through the sense of touch, as well as the conventional and state-of-the-art technologies of tactile actuators for tactile feedback delivery