Workshop on "Robotic assembly of 3D MEMS".

Proceedings of a workshop proposed in IEEE IROS'2007.The increase of MEMS' functionalities often requires the integration of various technologies used for mechanical, optical and electronic subsystems in order to achieve a unique system. These different technologies have usually process incompatibilities and the whole microsystem can not be obtained monolithically and then requires microassembly steps. Microassembly of MEMS based on micrometric components is one of the most promising approaches to achieve high-performance MEMS. Moreover, microassembly also permits to develop suitable MEMS packaging as well as 3D components although microfabrication technologies are usually able to create 2D and "2.5D" components. The study of microassembly methods is consequently a high stake for MEMS technologies growth. Two approaches are currently developped for microassembly: self-assembly and robotic microassembly. In the first one, the assembly is highly parallel but the efficiency and the flexibility still stay low. The robotic approach has the potential to reach precise and reliable assembly with high flexibility. The proposed workshop focuses on this second approach and will take a bearing of the corresponding microrobotic issues. Beyond the microfabrication technologies, performing MEMS microassembly requires, micromanipulation strategies, microworld dynamics and attachment technologies. The design and the fabrication of the microrobot end-effectors as well as the assembled micro-parts require the use of microfabrication technologies. Moreover new micromanipulation strategies are necessary to handle and position micro-parts with sufficiently high accuracy during assembly. The dynamic behaviour of micrometric objects has also to be studied and controlled. Finally, after positioning the micro-part, attachment technologies are necessary

A multi-fingered micromechanism for coordinated micro/nano manipulation,"

ABSTRACT Micromanipulators for coordinated manipulation of microand nano-scale objects are critical for advancing several emerging applications such as microassembly and manipulation of biological cells. Most of existing designs for micromanipulators accomplish either primarily microgripping or primarily micropositioning tasks, and relatively, only a very few are capable of accomplishing both microgripping and micropositioning, however, they are generally bulky. This paper presents conceptualization, design, fabrication and experimental characterization a novel micromanipulation station for coordinated planar manipulation combining both gripping and positioning of micro-and nano-scale objects. Conceptually, the micromanipulation station is comprised of multiple, independently actuated, fingers capable of coordinating with each other to accomplish the manipulation and assembly of micron-scale objects within a small workspace. A baseline design is accomplished through a systematic design optimization of each finger maximizing the workspace area of the manipulation station using the optimization toolbox in MATLAB. The device is micromachined on a SOI (silicon-oninsulator) wafer using the DRIE (Deep Reactive Ion Etching) process. The device prototype is experimentally characterized for the output displacement characteristics of each finger for known input displacements applied through manual probing. An excellent correlation between the experimental results and the theoretical results obtained through a finite element analysis in ANSYS software, which validates both the design and the fabrication of the proof-of-the-concept, is demonstrated

A microgripper for single cell manipulation

This thesis presents the development of an electrothermally actuated microgripper for the manipulation of cells and other biological particles. The microgripper has been fabricated using a combination of surface and bulk micromachining techniques in a three mask process. All of the fabrication details have been chosen to enable a tri-layer, polymer (SU8) - metal (Au) - polymer (SU8), membrane to be released from the substrate stress free and without the need for sacrificial layers. An actuator design, which completely eliminates the parasitic resistance of the cold arm, is presented. When compared to standard U-shaped actuators, it improves the thermal efficiency threefold. This enables larger displacements at lower voltages and temperatures. The microgripper is demonstrated in three different configurations: normally open mode, normally closed mode, and normally open/closed mode. It has-been modelled using two coupled analytical models - electrothermal and thermomechanical - which have been custom developed for this application. Unlike previously reported models, the electrothermal model presented here includes the heat exchange between hot and cold arms of the actuators that are separated by a small air gap. A detailed electrothermomechanical characterisation of selected devices has permitted the validation of the models (also performed using finite element analysis) and the assessment of device performance. The device testing includes electrical, deflection, and temperature measurements using infrared (IR) thermography, its use in polymeric actuators reported here for the first time. Successful manipulation experiments have been conducted in both air and liquid environments. Manipulation of live cells (mice oocytes) in a standard biomanipulation station has validated the microgripper as a complementary and unique tool for the single cell experiments that are to be conducted by future generations of biologists in the areas of human reproduction and stem cell research

Fast identification algorithms for manipulating biological cells

The physical manipulation of biological cells is very attractive now in biotechnology (Butler, 1991)) because it opens the possibility of examining and manipulating single molecules. Other methods are based on chemical effects, electrical effects, etc., and they generally do not allow researchers to examine single molecules cell and, thus, to understand their interaction which may encode many useful pieces of information. Such physical manipulation is fully performed by robotic devices. In order to automate the process of physical manipulation, micro machine vision for the fast identification of the objects involved is required. Typical objects that are involved are cells, cell elements, holders and injectors. In the research described in this thesis, which was carried out in the Advanced Engineering Design Laboratory of the Mechanical Engineering Department, University of Saskatchewan, algorithms for the three objects (the cell, holder and injector) were developed, implemented and tested. The results obtained have shown that the fastest identification times for these three objects are respectively 0.12s for the cell oocyte, 6.78s/100 frames for the holder, and 6.72s/100 frames for the injector. These performances are acceptable in the context of the physical manipulation of biological cells. The goal of the research described in this thesis was to develop algorithms that would give a fast recognition of the cell manipulation system. With the aid of the algorithms, an automatic operation of the cell manipulation system would be achieved. Image process and pattern recognition techniques were used in developing the Visual C++ GUI algorithms that would automatically recognize the components of the cell manipulation system for the purpose of manipulating the cells

Automated Micromanipulation of Micro Objects

In recent years, research efforts in the development of Micro Electro Mechanical Systems, (MEMS) including microactuators and micromanipulators, have attracted a great deal of attention. The development of microfabrication techniques has resulted in substantial progress in the miniaturization of devices such as electronic circuits. However, the research in MEMS still lags behind in terms of the development of reliable tools for post-fabrication processes and the precise and dexterous manipulation of individual micro size objects. Current micromanipulation mechanisms are prone to high costs, a large footprint, and poor dexterity and are labour intensive. To overcome such, the research in this thesis is focused on the utilization of microactuators in micromanipulation. Microactuators are compliant structures. They undergo substantial deflection during micromanipulation due to the considerable surface micro forces. Their dominance in governing micromanipulation is so compelling that their effects should be considered in designing microactuators and microsensors. In this thesis, the characterization of the surface micro forces and automated micromanipulation are investigated. An inexpensive experimental setup is proposed as a platform to replace Atomic Force Microscopy (AFM) for analyzing the force characterization of micro scale components. The relationship between the magnitudes of the surface micro forces and the parameters such as the velocity of the pushing process, relative humidity, temperature, hydrophilicity of the substrate, and surface area are empirically examined. In addition, a precision automated micromanipulation system is realized. A class of artificial neural networks (NN) is devised to estimate the unmodelled micro forces during the controlled pushing of micro size object along a desired path. Then, a nonlinear controller is developed for the controlled pushing of the micro objects to guarantee the stability of the closed loop system in the Lyapunov sense. To validate the performance of the proposed controller, an experimental setup is designed. The application of the proposed controller is extended to precisely push several micro objects, each with different characteristics in terms of the surface micro forces governing the manipulation process. The proposed adaptive controller is capable of learning to adjust its weights effectively when the surface micro forces change under varying conditions. By using the controller, a fully automated sequential positioning of three micro objects on a flat substrate is performed. The results are compared with those of the identical sequential pushing by using a conventional linear controller. The results suggest that artificial NNs are a promising tool for the design of adaptive controllers to accurately perform the automated manipulation of multiple objects in the microscopic scale for microassembly

Control of micromanipulation in the presence of van der waals force

Master'sMASTER OF ENGINEERIN

Micro parylene actuators for aqueous cellular manipulation.

Chan, Ho Yin.Thesis (M.Phil.)--Chinese University of Hong Kong, 2003.Includes bibliographical references (leaves 92-94).Abstracts in English and Chinese.ABSTRACT --- p.i摘要 --- p.iiiACKNOWLEDGEMENTS --- p.ivPUBLISHED PAPERS --- p.viTABLE OF CONTENTS --- p.viiLIST OF FIGURES --- p.ixLIST OF TABLES --- p.xiChapter Chapter 1 --- Introduction --- p.1Chapter 1.1 --- Traditional methods of cell manipulation --- p.1Chapter 1.2 --- New methods of cell manipulation using MEMS technology --- p.2Chapter 1.2.1 --- Electrostatic actuation --- p.2Chapter 1 2.2 --- Shape memory effect --- p.4Chapter 1.2.3 --- Pneumatic --- p.5Chapter 1.2.4 --- Electromagnetic --- p.5Chapter 1.2.5 --- Thermal --- p.6Chapter 1.3 --- Objective of this project --- p.1Chapter Chapter 2 --- Literature review --- p.11Chapter Chapter 3 --- "Design, modeling and heat transfer analysis" --- p.14Chapter 3.1 --- Design and the temperature-radius relationship of thermal actuators --- p.14Chapter 3.2 --- Heat transfer analysis --- p.17Chapter 3.2.1 --- Heat dissipation from the actuator --- p.18Chapter 3.2.2 --- Thermal transient response in liquid environment --- p.23Chapter 3.3 --- "Temperature, radius of curvature and tip deflection and actuation voltage relationship" --- p.24Chapter Chapter 4 --- Fabrication process of the thermal actuators --- p.28Chapter 4.1 --- Basic processes involved in fabricating the thermal actuators --- p.28Chapter 4.1.1 --- Photolithography --- p.28Chapter 4.1.1.1 --- Spin on and pattern photoresist --- p.29Chapter 4.1.1.2 --- Methods for alignment --- p.31Chapter 4.1.2 --- Lift off and etching processes --- p.33Chapter 4.1.3 --- Sacrificial release process --- p.35Chapter 4.1.4 --- Deposition --- p.38Chapter 4.1.4.1 --- Sputtering --- p.39Chapter 4.1.4.2 --- Thermal evaporation --- p.39Chapter 4.1.4.3 --- Thermal oxidation --- p.40Chapter 4.1.4.4 --- Parylene deposition --- p.41Chapter 4.2 --- Fabrication process of thermal actuators/grippers --- p.45Chapter 4.2.1 --- Fabrication of thermal actuators --- p.45Chapter 4.2.1.1 --- Mask design and making --- p.45Chapter 4.2.1.2 --- Process flow --- p.49Chapter 4.2.1.3 --- Fabricated samples --- p.53Chapter 4.2.1.4 --- Problems encountered during fabrication process --- p.54Chapter 4.2.2 --- Fabrication of multi-finger gripper --- p.55Chapter 4.2.2.1 --- Mask design --- p.55Chapter 4.2.2.2 --- Process flow --- p.57Chapter 4.2.2.3 --- Fabricated samples --- p.57Chapter Chapter 5 --- Testing thermal actuators --- p.58Chapter 5.1 --- Actuation by applying voltage (underwater) --- p.58Chapter 5.1.1 --- Experimental setup --- p.58Chapter 5.1.2 --- Experimental results --- p.59Chapter 5.1.3 --- Discussion --- p.63Chapter 5.2 --- Actuation by water bath heating --- p.66Chapter 5.2.1 --- Experimental setup --- p.66Chapter 5.2.2 --- Experimental results --- p.66Chapter 5.2.3 --- Discussion --- p.68Chapter 5.3 --- Frequency response and force analysis --- p.69Chapter 5.3.1 --- Frequency response --- p.69Chapter 5.3.2 --- Force analysis --- p.70Chapter Chapter 6 --- Cell grasping system --- p.73Chapter 6.1 --- Demonstration of cell grasping using single arm gripper --- p.73Chapter 6.2 --- MEMS chip with multi-finger grippers --- p.75Chapter 6.2.1 --- Mask design for MEMS chip --- p.76Chapter 6.2.2 --- Actuation of thermal gripper in air --- p.78Chapter 6.2.3 --- Demonstration of actuation and cell grasping --- p.79Chapter 6.2.4 --- A flexible cell grasping motion --- p.80Chapter 6.3 --- Proposed cell grasping system --- p.82Chapter Chapter 7 --- Summary and future work --- p.83Chapter 7.1 --- Summary --- p.83Chapter 7.2 --- Future work --- p.84APPENDIX --- p.87BIBLIOGRAPHY --- p.9

Design, characterisation and testing of SU8 polymer based electrothermal microgrippers

Microassembly systems are designed to combine micro-component parts with high accuracy. These micro-components are fabricated using different manufacturing processes in sizes of several micrometers. This technology is essential to produce miniaturised devices and equipment, especially those built from parts requiring different fabrication procedures. The most important task in microassembly systems is the manipulator, which should have the ability to handle and control micro-particles. Different techniques have been developed to carry out this task depending on the application, required accuracy, and cost. In this thesis, the most common methods are identified and briefly presented, and some advantages and disadvantages are outlined. A microgripper is the most important device utilized to handle micro-objects with high accuracy. However, it is a device that can be used only in sequential microassembly techniques. It has the potential to become the most important tool in the field of micro-robotics, research and development, and assembly of parts with custom requirements. Different actuation mechanisms are employed to design microgrippers such as electromagnetic force, electrostatic force, piezoelectric effect, and electrothermal expansions. Also, different materials are used to fabricate these microgrippers, for example metals, silicon, and polymers such as SU-8. To investigate the limitation and disadvantages of the conventional SU-8 electrothermal based microgrippers, different devices designed and fabricated at IMT, Romania, were studied. The results of these tests showed a small end-effector displacement and short cycling on/off (lifetime). In addition, the actuator part of these microgrippers was deformed after each operation, which results in reduced displacement and inconsistent openings at off state every time it was operated in a power ON/OFF cycle. One of these limitations was caused by the existence of conductors in arms of the end-effectors. These conductor designs have two disadvantages: firstly, it raises temperature in the arms and causing an expansion in the opposite direction of the desired displacement. Secondly, since the conductors pass through the hinges, they should be designed wide enough to reduce the conductor resistance as much as possible. Therefore, the wider the hinges are, the higher the in-plane stiffness and the less out of plane deflection. As a result, it increases the reaction force of the arm reducing the effect of deformation. Based on these limitations a new actuatorstructure of L-shape was proposed to reduce the effects of these drawbacks. This actuator has no conductor in the hinges or the arms of the end-effectors which reduce limitation on the hinge width. . In addition, a further development of this actuator was proposed to increase the stiffness of the actuator by doubling its thickness compared with the other parts of the griper. The results of this actuator proved the improvement in performance and reduction of the actuator deformation. This new actuator structure was used to design several different microgrippers with large displacement and suitable for a wide range of applications. Demonstrations of the capabilities of the microgrippers to be used in microassembly are presented. In addition, a novel tri-directional microactuator is proposed in this thesis. This actuator’s end-effector is capable of displacements in three different directions. This actuator was used with the other designs to develop a novel three-arm (three fingers) multidirectional microgripper. To study the microgripper displacement as a function to the heater temperature, the TCR of the conductor layer of each device was measured. Because different configurations of conductor layers were studied, a significant effect of the metal layer structure on TCR was discovered. The TCR value of gold film is reduced significantly by adding the chromium layers below and about it which were used to improve the adhesion between the gold film and the SU layers. In this thesis, a new method based on a robotic system was developed to characterise these microgrippers and to study the steady state, dynamic response, and reliability (lifetime cycling on/off). An electronic interface was developed and integrated to the robotic system to control and drive the microgrippers. This new system was necessary to carry out automated testing of the microgrippers with accurate and reliable results. Four different new groups of microgrippers were designed and studied. The first group was indirectly actuated using an L-Shaped actuator and two different actuator widths. The initial opening was 120 μm for both designs. The maximum displacement was about 140 μm for both designs. However, the actuator in the wider heater width showed more stable behavior during the cycling and the dynamic tests. The second group was based on direct actuation approach using the L-Shaped actuator. There were eight different designs based on this method with different heater conductor shape, actuator width, and arm thickness. The initial opening was 100 μm and there were different displacements for the eight designs. The study of these microgrippers proved that the actuator stiffness has a significant effect on the microgripper displacement. In addition, the shape of the heater conductor has less effect. The largest displacement achieved using this method of design was about 70 μm. The third group was designed for dual mode operation and has three different designs. The initial openings were 90 μm and 250 μm. The displacement was about 170 μm in both modes. The last microgripper design was a tri-arm design for multi-mode operation. The lifetime study of SU8 based microgrippers in this thesis was the first time such an investigation was carried out. The results of IMT designs showed that the larger is the displacement the less stable is the gripper design because of the high rection force acting on the actuators. The L-shape based microgrippers had better performance and they did not break after more than 400 cycles. In addition, the studies of static displacement and dynamic response of different designed microgripper proved that better performance of the proposed actuator can be obtained by using double thickness for the actuator as compared to the arm thickness

Magnetic Levitation of Polymeric Photo-thermal Microgrippers

Precise manipulation of micro objects became great interest in engineering and science with the advancements in microengineering and microfabrication. In this thesis, a magnetically levitated microgripper is presented for microhandling tasks. The use of magnetic levitation for positioning reveals the problems associated with modeling of complex surface forces and the use of jointed parts or wires. The power required for the levitation of the microgripper is generated by an external drive unit that makes further minimization of the gripper possible. The gripper is made of a biocompatible material and can be activated remotely. These key features make the microgripper a great candidate for manipulation of micro components and biomanipulation. In order to achieve magnetic levitation of microrobots, the magnetic field generated by the magnetic levitation setup is simulated. The magnetic flux density in the air gap region is improved by the integration of permanent magnets and an additional electromagnet to the magnetic loop assembly. The levitation performance is evaluated with millimeter size permanent magnets. An eddy current damping method is implemented and the levitation accuracy is doubled by reducing the positioning error to 20.3 µm. For a MEMS-compatible microrobot design, the electrodeposition of Co-Ni-Mn-P magnetic thin films is demonstrated. Magnetic films are deposited on silicon substrate to form the magnetic portion of the microrobot. The electrodeposited films are extensively characterized. The relationship between the deposition parameters and structural properties is discussed leading to an understanding of the effect of deposition parameters on the magnetic properties. It is shown that both in-plane and out-of-plane magnetized films can be obtained using electrodeposition with slightly differentiated deposition parameters. The levitation of the electrodeposited magnetic samples shows a great promise toward the fabrication of levitating MEMS devices. The end-effector tool of the levitating microrobot is selected as a microgripper that can achieve various manipulation operations such as pulling, pushing, tapping, grasping and repositioning. The microgripper is designed based on a bent-beam actuation technique. The motion of the gripper fingers is achieved by thermal expansion through laser heat absorption. This technique provided non-contact actuation for the levitating microgripper. The analytical model of the displacement of the bent-beam actuator is developed. Different designs of microgripper are fabricated and thoroughly characterized experimentally and numerically. The two microgripper designs that lead to the maximum gripper deflection are adapted for the levitating microrobot. The experimental results show that the levitating microrobot can be positioned in a volume of 3 x 3 x 2 cm^3. The positioning error is measured as 34.3 µm and 13.2 µm when electrodeposited magnets and commercial permanent magnets are used, respectively. The gripper fingers are successfully operated on-the-fly by aligning a visible wavelength laser beam on the gripper. Micromanipulation of 100 µm diameter electrical wire, 125 µm diameter optical fiber and 1 mm diameter cable strip is demonstrated. The microgripper is also positioned in a closed chamber without sacrificing the positioning accuracy

Automatic Microassembly of Tissue Engineering Scaffold

Ph.DDOCTOR OF PHILOSOPH