A microgripper using piezoelectric actuation for micro-object manipulation

Design, fabrication and tests of a monolithic compliant-flexure-based microgripper were performed. The geometry design and the material stresses were considered through the finite element analysis. The simulation model was used to study in detail profiles of von Mises stresses and deformation. The maximum stress in the microgripper is much smaller than the critical stress values for fatigue. The microgripper prototype was manufactured using micro-wire electrode discharge machining. A displacement amplification of 3.0 and a maximum stroke of 170 μm were achieved. The use of piezoelectric actuation allowed fine positioning. Micromanipulation tests were conducted to confirm potential applications of the microgripper with piezoelectric actuation in handling micro-objects. The simulation and experimental results have proven the good performance of the microgripper.     

Design and testing of a microgripper with SMA actuator for manipulation of micro components

The extremely high work-to-volume ratios of the SMA actuators make them suitable to be used as a powerful actuator in micro-scale manipulation. In this study, an easily manufacturable micro-gripper with shape memory alloy (SMA) wire actuator was designed and manufactured. The concept of the designed micro-gripper was based on flexible hinge structures to increase the deflection efficiency and strength. The size of microgripper was a significant criterion in our design. Also, innovative layout in locating of SMA wire caused the microgripper to gripe and manipulate a boarder range of objects. The finite element method was used to analyze and calculate the stress distribution and jaw’s deflection in the gripper. In order to verify the modeling results, an experimental analysis by building a set-up for micro-gripper and running tests were implemented and it showed a good agreement with the modeling results. The approximate size of the micro-gripper is about 12 × 10 mm and its maximum achievable deflection is 200 μm which is perceptibly higher than SMA actuated micro-grippers with the same size.

     

Electrothermoelastic modeling of MEMS gripper

The design of many thermal Microelectromechanical (MEMS) actuators is often based on finite element analysis, but lacks analytical insight. In this paper we report a novel electro-thermal microgripper and a comprehensive thermal modeling of a general 5 lineshape microbeam’s actuator using 1-D steady state heat equations. Because of the variety of microgripper fabrication technologies and their applications, different thermal boundary conditions are considered for lifted off and attached grippers. Parametric and nonparametric electrothermomechanical identification models for silicon on insulator microgripper, fabricated on 100 μm device layer, are obtained.     

A sub-micron metallic electrothermal gripper

We report the design, fabrication, and characterization of a multiple bent beam, sub-micron metallic electrothermal gripper. A bottom electroplating mold for electrodes was patterned using electron beam lithography in an SU-8, followed by nickel electroplating. A top electroplating mold for a sub-micron metallic gripper with high aspect ratio bent beams (thickness of 1 μm, width of 350 nm) was prepared using electron beam lithography in a polymethyl methacrylate (PMMA), followed by nickel electroplating and dry release of the top and bottom molds. The sub-micron gripper was characterized using a nanomanipulator system installed in a dual column scanning electron microscopy/focused ion beam system. The ability of the jaw to close up to 1.39 μm displacement with high precision and reliability has been reproducibly observed at an applied current of 28 mA, corresponding to the maximum power consumption of 11.2 mW. Finite element modeling displacement results performed using ANSYS for effective bent beam widths of 370 nm showed a good agreement with the measured displacement results. The sub-micron gripper demonstrated herein will enable the reproducible manipulations with nano-scale resolution displacement and could provide an effective means of interface between nano-scale objects and the micro/macro scale robotic systems.     

Design process and simulation testing of a shape memory alloy actuated robotic microgripper

Microgrippers are commonly used for micromanipulation of micro-objects with dimensions from 1 to 100 µm and attain features of reliable accuracy, low cost, wide jaw aperture and variable applied force. This paper studies the design process, simulation, and testing of a microgripper which can manipulate and assemble a platinum resistance temperature probe, made from a 25 µm diameter platinum wire, a 20 mm diameter tinned copper wire, and a printed circuit board type connector. Various microgripper structures and actuator types were researched and reviewed to determine the most suitable design for the required micromanipulation task. Operation tests using SolidWorks and ANSYS software were conducted to test a parallelogram structure with flexible single-notch hinges. The best suited material was found to be Aluminium alloy 7075-T6 as it was capable of producing a large jaw tip displacement of 0.7 mm without exceeding its tensile yield strength limit. A shape memory alloy was chosen as a choice of actuator to close the microgripper jaws. To ensure a repeatably accurate datum point, the final microgripper consisted of a fixed arm and a flexible arm. An optimisation process using ANSYS studied the hinge thickness and radius dimensions of the microgripper which improved its deflection whilst reducing the experienced stress.

     

Characterization of an electro-thermal micro gripper and tip sharpening using FIB technique

A micromachined electro-thermal gripper, first introduced by Ivanova et al. (Microelectron Eng 83:1393–1395, 2006), represents a promising candidate for the manipulation and handling of micro or even nano-scaled objects. To further optimize the performance of the device, a detailed electrical and mechanical characterization is needed. Due to the so-called duo-action gripper approach (i.e., a separate actuator for closing and opening action) these investigations focused on the maximum (minimum) opening width being 11.5 μm (3.3 μm), while in rest position a value of 4 μm is feasible. The maximum, electrical input power is limited to 80 mW/actuator element, resulting in a current density of up to 1.27 MA cm⁻² in the corresponding metal layers. When applying, however, larger current densities the probability of device failure increases substantially as in combination with an enhanced temperature of about 200°C electromigration effects occur in the metallization. Furthermore, the cut-off frequency and parasitic effects during actuation such as the z-deflection and the increase in length of each arm both showing values of up to 3 μm have been investigated as a function of operation parameters. Finally, the tips of the gripper were sharpened using Focused Ion Beam technique to a radius of less than 1 μm for gripping operations in space-restricted environments or for the manipulation or handling of sub-μm scaled objects.     

Multi-objective optimization design for a sand crab-inspired compliant microgripper

A large working travel and a minimal stress are the most critical characteristics of a microgripper but they are conflicted each other. This paper develops a new efficient hybrid algorithm to solve the multi-objective optimization design for a sand bubbler crab-inspired compliant microgripper. The structure of sand bubbler crab-inspired compliant microgripper is inspired from the profile of sand bubbler crab. A surrogate-assisted multi-objective optimization is conducted by developing a hybrid approach of finite element analysis, response surface method, Kigring metamodel and multi-objective genetic algorithm. First, the data are collected by integrating the finite element analysis and response surface method. Subsequently, in the types of common surrogates, Kigring metamodel is adopted as an efficient tool to approximate the objective functions. And then, the Pareto-optimal fronts are found via the multi-objective genetic algorithm. The results indicated that the optimal results are at the displacement of 5999.9 µm and stress of 330.68 MPa. The results revealed that the optimized results are highly consistent with both the validation results. The accuracy of the surrogate models showed that the regression model is a good prediction. The proposed approach is useful tool to solve complex optimization designs.

     

Metallic microgripper with SU-8 adaptor as end-effectors for heterogeneous micro/nano assembly applications

This paper presents design, fabrication, and characterization of easy-to-handle electroplated nickel microgrippers with SU-8 adaptors for heterogeneous micro/nano assembly applications. Two distinctive designs of microgrippers as end-effectors of micro/nano assembly applications have been developed in this work. The first design is 200 m thick electroplated nickel microgripper with a plastic mechanical displacement amplifier that is driven by a piezoelectric actuator. The piezoelectric actuator is capable of creating 5 m displacement which is amplified to 10 m by the plastic mechanical amplifier and finally such displacement generates 50–139 m microgripper tip displacement. The second design is 20 m thick electroplated nickel microgripper embedded in SU-8 adaptor for easy-to-handle operation. The second design is electro-thermally actuated using a set of joule-heated bent beams. With applied actuation voltage in the range of 2–4 V, the microgripper generates tip displacement of 4–32 m. Extensive thermal and mechanical finite element modeling have been carried out and measurement results were compared with the simulation results. Such developed easy-to-handle microgrippers can be used for micro/nano pick-and-place assembly applications.This work was supported by the National Institute of Standards and Technology-Advanced Technology Program (NIST-ATP 70NANB1H3021). The authors would like to thank the members of Design Engineering Group at Zyvex Corporation, Mr. Yohannes Desta from the Center for Advanced Microstructures and Devices (CAMD) at Louisiana State University for the valuable technical discussions, and the members of Micro and Nano Device and Systems (MiNDS) Laboratory and Cleanroom staffs at the University of Texas at Dallas.     

基于有限元分析的ICF靶半自动装配系统的微夹钳设计

根据惯性约束聚变(ICF)靶零件的特点,确定用于ICF靶半自动装配系统微夹钳的技术指标,并完成其结构设计.该微夹钳采用柔性铰链机构和压电陶瓷驱动,可根据需要更换不同形状和开口距离的夹口,以适应夹持不同靶零件.以压电陶瓷的2种极限参数为载荷,分析了微夹钳的张合量、应力分布、应变量,并采用非线性接触分析对夹持力和夹持效果进...     

Design,modeling and test of a novel compliant orthogonal displacement amplification mechanism for the compact micro-grasping system

In the compact micro-grasping system, the combination of precisely orthogonal movement transformation, displacement amplification and simple structure is important. The typical solution of the combination issue requires bidirectional symmetric input forces/displacements. However, under a certain driving condition, numerous actuators used in micro-manipulation only supply unidirectional input froce/displacement for the driven mechanism, which makes the typical solution infeasible. In this study, a novel compliant orthogonal displacement amplification mechanism (DAM) is proposed to solve the combination issue for numerous actuators used in micro-grasping. The proposed mechanism is a triangulation amplification-based mechanism with undetermined structural parameters. The number of the undetermined parameters and the solution principle are analyzed. The design process is presented. Finite element analysis (FEA) is used to verify the design method. The FEA results show that, for the design examples, the errors evaluating the orthogonal movement transformation are smaller than 0.56 % and 0.15 % respectively, and the displacement amplification ratios are larger than 4.6. The orthogonal displacement amplification is realized. A precise model of the displacement amplification ratio is derived. The dynamic performances of the proposed orthogonal DAM are modeled and FEA verified. Furthermore, a microgripper utilizing the proposed mechanism is presented. The performances of the gripper, including the displacement amplification and the parallel movement of the jaws, are verified by FEA and experiments.

     

Use of a PDMS spring element for ink jet printing applications

Results of the design, microfabrication and testing of a proof-of-concept, diaphragm-type silicone sealing joint are presented. DRIE-etched cavities were filled with a flexible sealing element made of polydimethylsiloxane that supports a silicon piston. A series of sealing joints were produced with variable widths, and the displacement of the piston was measured after applying pressures of up to 1 bar above atmospheric pressure in 0.2 bar increments. Two masks were designed to produce several sets of silicone springs with widths of 2–10.5 μm, each consisting of a 10 μm thick silicon piston that is 2 mm long. Tests performed on the shear spring joints were found to give a displacement of 0.5 μm at 1 bar when the sealing width is 6 μm or more. The sealing joint with a 10 μm width was found to give a displacement of 0.9 μm and an elastic recovery of 88%. The results showed this type of joint in the form of an elastically-deforming seal provides sufficient displacement for propelling liquid droplets as part of a liquid propulsion system.     

Design enhancement of a chevron electrothermally actuated microgripper for improved gripping performance

In this paper design modifications are proposed in microgripper design using two in-plane chevron electrothermal actuators. The design modifications are, converting free–free gripping arm into a clamped-free gripping arm and inclusion of the heat sinks in the shuttle. The modified design provides reduced temperature at the gripping jaws and higher gripping force. The proposed microgripper is modelled analytically and numerically using MEMS CAD tool CoventorWare. The performance of the microgripper such as displacement, force and temperature for the voltage range of 0–1.2 V is evaluated through numerical and analytical simulation. The results demonstrate the feasibility of fabrication. Further the gripper is made of polysilicon which allows operating the gripper at lower voltage.     

A three-phased circular electrode array for electro-osmotic microfluidic pumping

A circular micro-electrode array with three phases is designed and prototyped using PolyMUMPs process for AC electro-osmotic flow pumping. Finite element model of the micro electrode array has been developed using COMSOL Multiphysics^™. Performance of the electrode array is simulated and a double peak velocity phenomenon is found for this design, which is confirmed by experimental testing. Using ethanol as testing medium, the two time-averaged peak flow velocities are approximate 320 μm/s at 7 Hz and 850 μm/s at 100 Hz. It is found that the simulated and experimental results agree well.     

A novel electrostatic based microgripper (cellgripper) integrated with contact sensor and equipped with vibrating system to release particles actively

This paper presents design and simulation of a novel electrostatic microelectromechanical systems gripper with an integrated capacitive contact sensor. Moreover, this microgripper is able to employ vibration to release micro objects (cells) actively. Lateral comb drive system is used to close the gap between the gripper arms and hold the objects while the transverse comb differential capacitances act as a contact sensor to prevent damaging the fragile micron-sized particles specifically biological cells. In addition, the capability of the microgripper in generating vibration at the end-effectors electrostatically is an advantage to facilitate releasing process by overbalancing the adhesion forces between the particle and the gripper arm. Finite element analysis based simulations are carried out to estimate the behavior of the microgripper while the standard SOI-MUMPs micromachining process is proposed for fabrication of the microgripper.     

A multipurpose electrothermal microgripper for biological micro-manipulation

A novel electrothermal SU-8 microgripper with a large gripping scope and multipurpose jaws is designed and ANSYS software was used to check its performances. Then, the microgripper is fabricated by a simple UV-LIGA process followed by two performance tests. The static test results show that with only 195 mV, 111.1 mW and 53.7 °C temperature increase at the actuator, a 71.5 μm jaws gap change is obtained. The dynamic response test result shows that driven by different step-type voltages, the response time is about 0.23 s during both closing and opening jaws process. Finally, two micro-manipulation sequences are carried. The experimental results show that due to the large gripping scope and the multipurpose jaws, the microgripper can be used as a multipurpose manipulator for biological micro-manipulations including the manipulation of micro blood vessel and the operation of small size cell, such as cyanobacteria cell.     

Modeling and analysis of a 2-DOF bidirectional electro-thermal microactuator

In this paper, a four hot-arm U-shape electro-thermal actuator that can achieve bidirectional motion in two axes is introduced. By selectively applying voltage to different pairs of its four arms, the device can provide actuation in four directions starting from its rest position. It is shown that independent in-plane and out-of-plane motions can be obtained by tailoring the geometrical parameters of the system. The lumped model of the microactuator was developed using electro-thermal and thermo-mechanical analyses and validated using finite element simulations. The device has been fabricated using PolyMUMPs and experimental results are in good agreement with the theoretical predictions. Total in-plane deflections of 4.8 μm (2.4 μm in either direction) and upward out-of-plane deflections of 8.2 μm were achieved at 8 V of input voltage. The large achievable deflections and the higher degree-of-freedom of the proposed device compared to its counterparts, foresee its use in diverse MEMS applications.     

Integrated micro Pirani gauge based hermetical package monitoring for uncooled VO x bolometer FPAs

This paper presents the design and fabrication of a micro Pirani gauge using VO _x as the sensitive material for monitoring the pressure inside a hermetical package for micro bolometer focal plane arrays (FPAs). The designed Pirani gauge working in heat dissipating mode was intentionally fabricated using standard MEMS processing which is highly compatible with the FPAs fabrication. The functional layer of the micro Pirani gauge is a VO _x thin film designed as a 100 × 200 μm pixel, suspended 2 μm above the substrate. By modeling of rarefied gas heat conduction using the Extended Fourier’s law, finite element analysis is used to investigate the sensitivity of the pressure gauge. Also the thermal interactions between the micro Pirani gauge and bolometer FPAs are verified. From the fabricated prototype, the measured device TCR is about −0.8% K⁻¹ and the sensitivity about 1.84 × 10⁻³ W K⁻¹ mbar⁻¹.     

Microgrippers created in microstructurable glass

 In this paper a new microgripper will be presented. The specific feature is the microfabrication based on a UV-lithographic process in microstructurable, photosensitive glass. Technological and manufacturing problems of the gripper will be described. The developed microgripper is actuated by a piezoelectric ceramic (monomorph). Glass microstructures are used as solid state hinges. With the special design of the gripper it is possible to realise a high distance ratio. The deflection of the gripping arms is some hundred micrometers. The gripping forces are a few mN up to 50 mN. The new grippers were fabricated and tested successfully. Received: 20 December 1996/Accepted: 9 January 1997     

Effect of electrode size and silicon residue on piezoelectric thin-film membrane actuators

Piezoelectric micro-electromechanical systems (MEMS) often adopt a membrane structure to facilitate sensing or actuation. Design parameters, such as membrane size, thickness of the piezoelectric thin film, and electrode types, have been studied to maximize actuation, sensitivity, or coupling coefficient. This paper is to demonstrate numerically and experimentally that the size of silicon residue and its relative size to the top electrode are two critical yet unrecognized parameters in maximizing the actuation displacement of PZT thin-film membrane actuators. To study effects of the silicon residue, we have developed a finite element model using ANSYS. The model consists of five components: a square passive silicon membrane, a silicon substrate, a PZT thin film, a square top electrode, and a silicon residue region. In particular, the silicon residue has a circular inner diameter and a square outer perimeter with a trapezoidal cross section. Predictions of the finite element model lead to several major results. First, when the silicon residue is present, there exists an optimal size of the top electrode maximizing the actuator displacement. Second, the optimal electrode size is roughly 50–60% of the inner diameters of the silicon residue. The displacement of the membrane actuator declines significantly as the electrode overlaps with the silicon residue. Third, the maximal actuator displacement decreases as the inner diameter of the silicon residue decreases. Aside from the finite element analysis, a mechanics-of-material model is also developed to predict the electrode size that maximizes the actuator displacement. To verify the simulation results, eight PZT thin-film membrane actuators with progressive electrode sizes are fabricated. These actuators all have a square membrane of 800 μm × 800 μm with the inner diameter of the silicon residue controlled between 500 and 750 μm. A laser Doppler vibrometer is used to measure the actuator displacements. The experimental measurements confirm that there exists an optimal size of the top electrode maximizing the actuator displacement.     

Design, fabrication and testing of a high performance silicon piezoresistive Z-axis accelerometer with proof mass-edge-aligned-flexures

This paper presents design, fabrication and testing of a quad beam silicon piezoresistive Z-axis accelerometer with very low cross-axis sensitivity. The accelerometer device proposed in the present work consists of a thick proof mass supported by four thin beams (also called as flexures) that are connected to an outer supporting rim. Cross-axis sensitivity in piezoresistive accelerometers is an important issue particularly for high performance applications. In the present study, low cross-axis sensitivity is achieved by improving the device stability by placing the four flexures in line with the proof mass edges. Various modules of a finite element method based software called CoventorWare^™ was used for design optimization. Based on the simulation results, a flexure thickness of 30 μm and a diffused resistor doping concentration of 5 × 10¹⁸ atoms/cm³ were fixed to achieve a high prime-axis sensitivity of 122 μV/Vg, low cross-axis sensitivity of 27 ppm and a relatively higher bandwidth of 2.89 kHz. The designed accelerometer was realized by a complementary metal oxide semiconductor compatible bulk micromachining process using a dual doped tetra methyl ammonium hydroxide etching solution. The fabricated accelerometer devices were tested up to 13 g static acceleration using a rate table. Test results of fabricated devices with 30 μm flexure thickness show an average prime axis sensitivity of 111 μV/Vg with very low cross-axis sensitivities of 0.652 and 0.688 μV/Vg along X-axis and Y-axis, respectively.