Design and fabrication of a planar three-DOFs MEMS-based manipulator

This paper presents the design, modeling, and fabrication of a planar three-degrees-of-freedom parallel kinematic manipulator, fabricated with a simple two-mask process in conventional highly doped single-crystalline silicon (SCS) wafers (100). The manipulator’s purpose is to provide accurate and stable positioning of a small sample (10 × 20 × 0.2 μm3), e.g., within a transmission electron microscope. The manipulator design is based on the principles of exact constraint design, resulting in a high actuation-compliance combined with a relatively high suspension stiffness. A modal analysis shows that the fourth vibration mode frequency is at least a factor 11 higher than the first three actuation-related mode frequencies. The comb-drive actuators are modeled in combination with the shuttle suspensions gaining insight into the side and rotational pull-in stability conditions. The two-mask fabrication process enables high-aspect-ratio structures, combined with electrical trench insulation. Trench insulation allows structures in conventional wafers to be mechanically connected while being electrically insulated from each other. Device characterization shows high linearity of displacement wrt voltage squared over ±10 μm stroke in the x- and y-directions and ±2◦ rotation at a maximum of 50 V driving voltage. Out-of-plane displacement crosstalk due to in-plane actuation in resonance is measured to be less than 20 pm. The hysteresis in SCS, measured using white light interferometry, is shown to be extremely small

A novel actuator-internal micro/nano positioning stage with an arch-shape bridge type amplifier

This paper presents a novel actuator-internal two degree-of-freedom (2-DOF) micro/nano positioning stage actuated by piezoelectric (PZT) actuators, which can be used as a fine actuation part in dual-stage system. To compensate the positioning error of coarse stage and achieve a large motion stroke, a symmetrical structure with an arch-shape bridge type amplifier based on single notch circular flexure hinges is proposed and utilized in the positioning stage. Due to the compound bridge arm configuration and compact flexure hinge structure, the amplification mechanism can realize high lateral stiffness and compact structure simultaneously, which is of great importance to protect PZT actuators. The amplification mechanism is integrated into the decoupling mechanism to improve compactness, and to produce decoupled motion in X- and Y- axes. An analytical model is established to explore the static and dynamic characteristics, and the geometric parameters are optimized. The performance of the positioning stage is evaluated through finite element analysis (FEA) and experimental test. The results indicate that the stage can implement 2-DOF decoupled motion with a travel range of 55.4×53.2 μm2, and the motion resolution is 8 nm. The stage can be used in probe tip-based micro/nano scratching

Design and computational optimization of a flexure-based XY nano-positioning stage

This thesis presents the design and computational optimization of a two-axis nano-positioning stage. The devised stage relies on double parallelogram flexure bearings with under-constraint eliminating linkages to enable motion in the primary degrees-of-freedom. The structural parameters of the underlying flexures were optimized to provide a large-range and high bandwidth with sub-micron resolution while maintaining a compact size. A finite element model was created to establish a functional relationship between the geometry of the flexure elements and the stiffness behavior. Then, a neural network was trained from the simulation results to explore the design space with a low computational expense. The neural net was integrated with a genetic algorithm to optimize the design of the flexures for compactness and dynamic performance. The optimal solutions resulted in a reduction of stage footprint by 14% and an increase in the first natural frequency by 75% relative to a baseline design, all while preserving the same 50mm range in each axis with a factor of safety of 2. This confirms the efficacy of the proposed approach in improving stage performance through an optimization of its constituent flexures.Mechanical Engineerin

Potentialities of optimal design methods and associated numerical tools for the development of new micro- and nanointelligent systems based on structural compliance - An example -

11 pagesInternational audienceThis paper deals with the interest and potential use of intelligent structures mainly based on compliant mechanisms (and optionally including smart materials), for the development of new micro- and nano-robotics devices. The state of the art in optimal design methods for the synthesis of intelligent compliant structures is briefly done. Then, we present the optimal method developed at CEA LIST, called FlexIn, and its new and still in development functionalities, which will be illustrated by a few simple design examples. An opening will be given about the possibility to address the field of Nanorobotics, while adding functionalities to the optimal design method

Synthesis of optimized compliant mechanisms for ultra-precision applications

Compliant mechanisms for ultra-precision applications are often required to achieve highest accuracy over largest possible ranges of motion along multiple axes. The typical synthesis approach for such high demands is based on the substitution of the revolute joints of a suitable rigid-body model with optimized flexure hinges. However, during the transition from rigid-body model to compliant mechanism, the effects of multiple input parameters are still widely unknown. Among them are the degrees of freedom of the rigid-body model, the integration of the drive elements, as well as the coupling of mechanisms to achieve multiple motion axes. The following contribution expands the fundamentals of the synthesis of compliant mechanisms based on rigid-body models for their application in ultra-precision technologies. Based on the investigation of the aforementioned parameters as well as the knowledge gained from previous research work, a novel synthesis method has been developed

DEVELOPMENT OF A NOVEL Z-AXIS PRECISION POSITIONING STAGE WITH MILLIMETER TRAVEL RANGE BASED ON A LINEAR PIEZOELECTRIC MOTOR

Piezoelectric-based positioners are incorporated into stereotaxic devices for microsurgery, scanning tunneling microscopes for the manipulation of atomic and molecular-scale structures, nanomanipulator systems for cell microinjection and machine tools for semiconductor-based manufacturing. Although several precision positioning systems have been developed for planar motion, most are not suitable to provide long travel range with large load capacity in vertical axis because of their weights, size, design and embedded actuators. This thesis develops a novel positioner which is being developed specifically for vertical axis motion based on a piezoworm arrangement in flexure frames. An improved estimation of the stiffness for Normally Clamped (NC) clamp is presented. Analytical calculations and finite element analysis are used to optimize the design of the lifting platform as well as the piezoworm actuator to provide maximum thrust force while maintaining a compact size. To make a stage frame more compact, the actuator is integrated into the stage body. The complementary clamps and the amplified piezoelectric actuators based extenders are designed such that no power is needed to maintain a fixed vertical position, holding the payload against the force of gravity. The design is extended to a piezoworm stage prototype and validated through several tests. Experiments on the prototype stage show that it is capable of a speed of 5.4 mm/s, a force capacity of 8 N and can travel over 16 mm

Design of three degrees-of-freedom motion stage for micro manipulation

A miniaturized translational motion stage has potentials to provide not only performances equivalent to conventional motion stages, but also additional features from its small form factor and low cost. These properties can be utilized in applications requiring a small space such as a vacuum chamber in a scanning electron microscopy (SEM), where hidden surface can decrease by manipulating objects to measure. However, existing miniaturized motion stages still have several cm3 level volumes and provide simple operations. In this dissertation, Micro-electro-mechanical systems (MEMS)-based motion stages are utilized to replace a miniaturized motion stage for micro-scale manipulation and possible applications. However, most MEMS fabrication methods remain in monolithic fabrication methods and a lot of MEMS based multiple degrees-of-freedom (DOFs) motion stage also remain for in-plane motions. In this dissertation, a nested structure based on a serial kinematic mechanism is implemented in order to overcome these constraints and implement out-of-plane motion, where one independent stage is embedded into the other individual stage with additional features for structurally and electrically isolations among the engaged stages. MEMS actuators and displacement amplifiers are also investigated for reasonable performance. 3-axis motions are divided into two in-plane motions and one out-of-plane motion; an in-plane 1 DOF motion stage (called an X-stage) and one out-of-plane 1 DOF motion stage (called a Z-stage) are designed and characterized experimentally. Based on the two stages, the XY-stage is designed by merging one X-stage into the motion platform of the other X-stage with a different orientation (called an XY-stage). With this nested approach, the fabricated XY-stage demonstrated in-plane motions larger than 50 µm with ignorable coupled motion errors. Based on this nested approach, the 3-axis motion stage is also implemented by utilizing the nested structure twice; integrating the Z-stage with the motion platform of the XY-stage (called an XYZ-stage). The XYZ-stage demonstrated out-of-plane motions about 23 µm as well as the in-plane motions. Two presented motion stages have been utilized in the manipulation of micro-scale object by the cooperation of the two XY-stages inside a SEM chamber. The large motion platform of the X-stage is also utilized in a parallel plate type rheometer to measure the material properties of viscoelastic materials

PKM mechatronic clamping adaptive device

This study proposes a novel adaptive fixturing device based on active clamping systems for smart micropositioning of thin-walled precision parts. The modular architecture and the structure flexibility make the system suitable for various industrial applications. The proposed device is realized as a Parallel Kinematic Machine (PKM), opportunely sensorized and controlled, able to perform automatic error-free workpiece clamping procedures, drastically reducing the overall fixturing set-up time. The paper describes the kinematics and dynamics of this mechatronic system. A first campaign of experimental trails has been carried out on the prototype, obtaining promising results