Force Characterization of a Rotary Motion Electrostatic Actuator based on Finite Element Method (FEM) Analysis

Two types of rotary motion electrostatic actuators were designed and analyzed using Finite Element Method (FEM) analysis. This paper discussed the comparisons and detailed thrust force analysis of the two actuators. Both designs have similar specifications; i.e the number of rotor’s teeth to stator’s teeth ratio, radius and thickness of rotor, and gap between stator and rotor. Two structures were designed & evaluated; (a) Side-Driven Electrostatic Actuator and (b) Bottom-Driven Electrostatic Actuator. The paper focuses on comparing & analyzing the generated electrostatic thrust force for both designs when the electrostatic actuator’s parameters are varied. Ansys Maxwell 3D software is used to design and analyze the generated thrust force of the two rotary motion electrostatic actuators. The FEM analyses have been carried out by (i) varying the actuator size; (ii), varying the actuator thickness and (iii) varying the actuator teeth ratio. The FEM analysis shows that the Bottom-Drive Electrostatic Actuator exhibit greater thrust force, 4931.80N compared to the Side-Drive Electrostatic Actuator, 240.96N; when the actuator’s radius is 700m, thickness is 50m, gap between the stator and rotor is 2m and the teeth ratio is 16:12

Large displacement vertical translational actuator based on piezoelectric thin films

A novel vertical translational microactuator based on thin-film piezoelectric actuation is presented, using a set of four compound bend-up/bend-down unimorphs to produce translational motion of a moving platform or stage. The actuation material is a chemical-solution deposited lead–zirconate–titanate (PZT) thin film. Prototype designs have shown as much as 120 µm of static displacement, with 80–90 µm displacements being typical, using four 920 µm long by 70 µm legs. Analytical models are presented that accurately describe nonlinear behavior in both static and dynamic operation of prototype stages when the dependence of piezoelectric coefficients on voltage is known. Resonance of the system is observed at a frequency of 200 Hz. The large displacement and high bandwidth of the actuators at low-voltage and low-power levels should make them useful to a variety of optical applications, including endoscopic microscopy.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/85407/1/jmm10_7_075016.pd

Design and fabrication of a large vertical travel silicon inchworm microactuator for the Advanced Segmented Silicon Space

Future concepts for ultra-large lightweight space telescopes include the telescopes with segmented silicon mirrors. This paper describes a proof-of-concept inchworm actuator designed to provide nanometer resolution, high stiffness, large output force, long travel range, and compactness for ultraprecision positioning applications in space. A vertically actuating inchworm microactuator is proposed to achieve large actuation travel by incorporating compliant beam structures within a silicon wafer. An inchworm actuator unit consists of a piezoelectric stack actuator, a driver, a pair of holders, a slider, and a pair of polymer beams connected to a centrally clamped flexure beam. Deep reactive ion etch experiments have been performed for constructing the actuator

Stepper microactuators driven by ultrasonic power transfer

Advances in miniature devices for biomedical applications are creating ever-increasing requirements for their continuous, long lasting, and reliable energy supply, particularly for implanted devices. As an alternative to bulky and cost inefficient batteries that require occasional recharging and replacement, energy harvesting and wireless power delivery are receiving increased attention. While the former is generally only suited for low-power diagnostic microdevices, the latter has greater potential to extend the functionality to include more energy demanding therapeutic actuation such as drug release, implant mechanical adjustment or microsurgery. This thesis presents a novel approach to delivering wireless power to remote medical microdevices with the aim of satisfying higher energy budgets required for therapeutic functions. The method is based on ultrasonic power delivery, the novelty being that actuation is powered by ultrasound directly rather than via piezoelectric conversion. The thesis describes a coupled mechanical system remotely excited by ultrasound and providing conversion of acoustic energy into motion of a MEMS mechanism using a receiving membrane coupled to a discrete oscillator. This motion is then converted into useful stepwise actuation through oblique mechanical impact. The problem of acoustic and mechanical impedance mismatch is addressed. Several analytical and numerical models of ultrasonic power delivery into the human body are developed. Major design challenges that have to be solved in order to obtain acceptable performance under specified operating conditions and with minimum wave reflections are discussed. A novel microfabrication process is described, and the resulting proof-of-concept devices are successfully characterized.Open Acces

Development of the technological process for the production of the electrostatic curved beam actuator for pneumatic microvalves

This work focuses on the development of an effective technological process for the production of the electrostatic curved beam actuator capable to be used as a driving element in different devices such as microswitches or microvalves. Main attention was drawn to the investigation of electroplating technique as a critical process in the microactuator fabrication as well as to the design of the actuator. In addition, usability of ceramic substrates for the microactuator and microvalve production was examined. The idea behind it was that ceramic substrates can be preprocessed and delivered already with necessary electrical connections on it. This would make the entire production process simpler and cheaper. Several types of polished alumina (Al2O3) substrates were used for this purpose. Electrostatic actuation principle was chosen for its good scaling properties to small dimensions, low power consumption, smaller size and higher switching speed. Curved shape of the actuator allows to reduce its pull-in voltage and thus to increase the amplitude of motion as compared to the parallel-plate structures. The material of the actuator is nickel. It was chosen for its good mechanical properties and relative simplicity of processing. Double layer nickel electroplating was used to produce the microactuator. The layers have different stress gradients controlled by current density during the electroplating process, making it possible to achieve the desired bending of the structure. Compared to bimetallic bending cantilever actuators, the curvature of the single-metal beam is less dependable on temperature and aging. Thus, more stable performance under changing working conditions was ensured. In order to avoid sticking of the microactuator to the isolation layer in the closed state, an array of stand-off bumps was added on the back-side of the beam. These bumps reduce the contact area and increase the distance between the actuator and the isolation layer. Fifteen design variants of the actuator differing in length and width were fabricated in order find the most effective solution for given system requirements. Based on the actuators technological process developed in this work, a simple electrostatic microvalve was designed and produced. Final variants of microvalve were fabricated on a standard 380 µm thick silicon wafer. Gas inlet channel as well as the electrodes and the actuator itself are all placed on the same substrate in order to reduce the size and cost of the system. During characterization, mechanical stability of the actuators and microvalves were studied by means of drop, temperature and shear tests in order to prove the reliability of the system. System performance tests proved stable pull-in voltages from 8,6 V to 11,6 V. Maximal gas flow through the valve was 110±5 ml/min at applied differential pressure of 2 bar

Optimal Observability-based Modelling, Design and Characterization of Piezoelectric Microactuators.

International audienceThis paper deals with the optimal design of monolithic piezoelectric microactuators with integrated proprioceptive sensors. Dedicated to the microrobotic and micromechatronic fields, these works detail the modelling and the characterization of compliant structures with integrated actuating and sensing elements. The proposed optimal design procedure adresses not only static criteria but also dynamic ones. This leads to microdevices which are more performant with regards to mechanical (displacement, force...) and control (dynamics, stability, precision) characteristics. Efficient design of such devices is achieved using a flexible building block method. A topological optimization method combined with an evolutionary algorithm is used to optimize the design of truss-like planar structure. This method chooses the best location among the different piezoelectric elements. Different mechanical, actuation or sensing elements are accordingly chosen from a data bank. From the control point of view, optimisation criteria are considered to enforce the observability of the vibrational dominant modes of the structure. Therefore, control and observation Gramians are exploited in the optimal design to shape the open loop frequency response of both, actuation and sensing functions of the integrated device. In the last part of the paper, based on these results, the optimal design and manufacturing of an innovative piezoelectric flexible microgripper is proposed. The prototype is manufactured from a monolithic piezoelectric material (PIC 151). Its reduced size (15 mm x 18 mm) fits the requirement of both microrobotics and micromechatronics applications, which is suitable for micromanipulation tasks. The characterization and the performance of this integrated microactuator finally close the paper and the efficiency of the optimal design procedure for micromechatronics applications are shown

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

Effect of electrode location and thickness ratio of flange and web on I cross section piezoelectric cantilever beam for its actuation capability

Present work deals with the numerical investigation of a cantilever beam having I cross section made up of piezoelectric material for its actuation capability. The beam is modeled under the assumption of Euler’s Bernoulli equation. Eight cases are considered for different electrode locations. The beam was subjected to voltage loads at different locations. It was noticed that tip deflection increases with increasing applied voltage across the electrodes. Maximum tip deflection was achieved with the increase in voltage with particular electrode arrangement. In this report we have also demonstrated that for downward tip deflection, there are two values of thickness ratio of flange and web for a given tip deflection at a given applied voltage

A reconfigurable tactile display based on polymer MEMS technology

This research focuses on the development of polymer microfabrication technologies for the realization of two major components of a pneumatic tactile display: a microactuator array and a complementary microvalve (control) array. The concept, fabrication, and characterization of a kinematically-stabilized polymeric microbubble actuator (¡°endoskeletal microbubble actuator¡±) were presented. A systematic design and modeling procedure was carried out to generate an optimized geometry of the corrugated diaphragm to satisfy membrane deflection, force, and stability requirements set forth by the tactile display goals. A refreshable Braille cell as a tactile display prototype has been developed based on a 2x3 endoskeletal microbubble array and an array of commercial valves. The prototype can provide both a static display (which meets the displacement and force requirement of a Braille display) and vibratory tactile sensations. Along with the above capabilities, the device was designed to meet the criteria of lightness and compactness to permit portable operation. The design is scalable with respect to the number of tactile actuators while still being simple to fabricate. In order to further reduce the size and cost of the tactile display, a microvalve array can be integrated into the tactile display system to control the pneumatic fluid that actuates the microbubble actuator. A piezoelectrically-driven and hydraulically-amplified polymer microvalve has been designed, fabricated, and tested. An incompressible elastomer was used as a solid hydraulic medium to convert the small axial displacement of a piezoelectric actuator into a large valve head stroke while maintaining a large blocking force. The function of the microvalve as an on-off switch for a pneumatic microbubble tactile actuator was demonstrated. To further reduce the cost of the microvalve, a laterally-stacked multilayer PZT actuator has been fabricated using diced PZT multilayer, high aspect ratio SU-8 photolithography, and molding of electrically conductive polymer composite electrodes.Ph.D.Committee Chair: Allen,Mark; Committee Member: Bucknall,David; Committee Member: Book,Wayne; Committee Member: Griffin,Anselm; Committee Member: Yao,Donggan