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An SU-8 polymeric actuator with an embedded silicon skeleton has recently been reported to have good actuation performance. As a composite, it has room for performance improvements by design. Yet, it has not been optimized for the best performance. In this paper, we perform a parametric study, based on analytical and finite-element models, to find the optimum design. Properties and actuation capabilities are related to design parameters of the composite. In a design case to maximize work density, the parametric study found an optimum design consisting of 70% SU-8 and 30% Si. As compared with pure SU-8, the optimum composite design has a Young's modulus that is 2.2 times higher, a thermal stress that is 2.5 times higher, a work density that is 2.6 times higher, a coefficient of thermal expansion that is 5% higher, and a shorter thermal-response time. The optimum design can deliver a maximum strain of 2.77% and a maximum stress of 196 MPa at the maximum operating temperature of 200°C. Moreover, it has a rather high work density of 2.71 MJ/m3, which is comparable with other thermal phase-change actuators. In conclusion, this polymeric composite actuator is very powerful for microactuation.

To develop a system integration process for a slider with an integrated microactuator (SLIM), quite a few challenges had to be resolved. They include processes for double rowbar stacking and thinning, chiplet mounting, slider separation, and chiplet cross crown fabrication, to name just a few. The slider separation process is particularly challenging: during this process, the mounting bars suspended on thin Si leaf springs are released. This paper discusses the challenges encountered and the system integration solutions developed.

This paper presents the design, fabrication, and implementation of a microcantilever actuator with magnetostatic latching for performing low power bistable relay applications. This unique bistable feature consists of a low-stiffness torsion/cantilever beam system with circular-shaped support and a permanent magnet for holding the closed state with a permalloy soft magnetic circuit. The special circular support is designed to enhance the stiffness of the overhang beams. First, mechanical modeling of the leveraged torsion/cantilever beams was performed by Castigliano's theorem so as to deduce the spring stiffness of system. Then the device has been prepared by a laminated photoresist sacrificial layer process (LPSLP). Finally, mechanical performance was characterized by atomic force microscopy (AFM), combined with finite element simulation using ANSYS(TM) package and analysis model as well. Switching between two stable states of the microactuator was successfully validated with WYKO NT1100 optical profiling system.

This paper reports the fabrication and characterization of two fully batch-fabricated electrodynamic microactuators. The actuators utilize wax-bonded Nd-Fe-B powder magnets and electroplated copper coils for electrodynamic actuation out of plane. A cantilever-type microactuator achieves a 2.66 ?m vertical deflection at a driving current of 5.5 mArms at 100 Hz. A piston-type actuator with elastomeric membrane obtained a 1.17 ?m vertical displacement at a driving current of 13.5 mArms at 100 Hz. These microactuators demonstrate the integrability of wax-bonded Nd-Fe-B powder magnets into microscale electromechanical transducers.

A key point for microrobots is represented by the actuation system, which enables them to move and manipulate objects, if required. In the field of mechatronic medical micro-instruments a micromotor could be used for the actuation of endoscopes lenses and in powered laparoscopic tools, for examples micro-grippers or micro-scissors, drug delivery micro-pumps and endoscopic intra-corporeal autonomous capsules. The size range of interest goes from centimetres down to hundreds of microns. Scaling down the overall dimensions of robots, traditional actuators are no longer feasible and it becomes essential to employ innovative systems. In this paper the optimization of an existing wobble micromotor is presented and its implementation as microactuator for biomedical devices has been demonstrated. The Finite Element Method (FEM) analysis has been applied on a variable reluctance wobble motor ( Φ 5 mm × 5 mm) in order to evaluate all the electric and magnetic quantities necessary for the optimization of the micromotor geometry and performances and to compute its electromechanical characteristic. Thanks to its small size, the micromotor has been assembled inside swallowable modules, both in single and in twin configuration. Motor's simple structure and low cost opens a very wide market where the actuator could be commercialized, as for example consumer electronics, mechatronic medical micro-instruments, robotics, micromanipulators, dosing systems and mobile robots.

This paper presents a novel microactuator driven by shape memory alloy (SMA). First, the helical spring-shaped SMA is fabricated from SMA wire (Ti50%-Ni45%-Cu5%) with one way shape memory effect and 0.6 mm in diameter. Subsequently, a compliant tube-type microactuator driven by helical spring-shaped SMA is developed. The performances of the helical spring-shaped SMA and the compliant tube-type microactuator, such as the response time, the recovery force and the surface temperature in terms of the driving currents, are investigated. The driving circuit system comprising a pulse width modulation (PWM) control circuit is used to drive the actuator. Experiments demonstrate that control of the SMA actuator using PWM effectively reduces the energy consumption and ensures a short cooling time to guarantee a high response time in actuating cycles. Finite element software (COSMOSWorks) is applied for the analysis of the compliant tube-type actuator, which aim is to demonstrate the agreement between the theoretical analysis and experiment as well as to improve the performance of the actuators.

Magnetic shape memory (MSM) materials present a new class of alloys, which can be used for creating electromagnetic microactuators facilitating a linear motion. The concept of the hybrid MSM microactuator pursued is using a pair of discrete MSM strips sandwiched between microstators. For the microstator fabrication, MEMS technology is applied. The two MSM strips are elongated alternatively, with one strip showing strain when exposed to a magnetizing field, while the other one is mechanically collapsed by its elongating counterpart, and vice versa. For inducing the elongation in the MSM strips, a critical field strength H crit has to be exceeded in vertical direction within the MSM strip. For analyzing what magnetic field strength is reached by the microstators and if it is greater than the critical field strength H crit required to inducing a reorientation of the twin variants in the MSM material, magneto-optical measurements were carried out.

An integrated system made up of a double-hot arm electro-thermal microactuator and a piezoresistor embedded at the base of the 'cold arm' is proposed. The electro-thermo-mechanical modeling and optimization is developed to elaborate the operation mechanism of the hybrid system through numerical simulations. For given materials, the geometry design mostly influences the performance of the sensor and actuator, which can be considered separately. That is because thermal expansion induced heating energy has less influence on the base area of the 'cold arm,' where is the maximum stress. The piezoresistor is positioned here for large sensitivity to monitor the in-plane movement of the system and characterize the actuator response precisely in real time. Force method is used to analyze the thermal induced mechanical expansion in the redundant structure. On the other hand, the integrated actuating mechanism is designed for high speed imaging. Based on the simulation results, the actuator operates at levels below 5 mA appearing to be very reliable, and the stress sensitivity is about 40 MPa per micron.

Scratch drive actuators (SDAs) are one of the important microelectromechanical devices that have been recently used for many applications. This paper presents a new analytical model for the scratch drive actuators to facilitate the design of this device. In order to model the working states of SDA, three different static modes are considered: non-contact mode, transitional mode, and full-contact mode. The SDA is simplified as an L-shape plate with different boundary conditions in each mode. Using Euler–Bernoulli theory, governing equations are derived and solved in every mode. The non-contact mode allows identifying the deflection and driving voltage at which the actuator plate reaches to the substrate. From the transitional mode, primary contact length is calculated and used for the analysis of full-contact mode. In the full-contact mode, where SDA is completely snapped down in its working cycle, the relationships between input voltage and design parameters, such as SDA geometry, contact length and step size, are obtained. In addition, output force, as another important design parameter, is characterized based on the physics and geometry of SDA. To validate our model, the results are also compared with accessible experimental data. This analytical model provides an efficient framework to estimate the design parameters of SDA before any expensive empirical process.

In this work, the nonlinear vibration characteristics of bimorph giant magnetostrictive thin film (GMF), TbDyFe/PI/SmFe, are measured and analyzed, firstly. Thereafter, by employing the primary resonance and superharmonic resonance performance of GMF cantilever, and simulating the ostraciiform locomotion of boxfish, an in-pipe wireless swimming microrobot is developed, whose caudal fin is fabricated by GMF microactuator. On the basis of the equivalent load model of magnetostrictive effect of GMF, the governing equations for swimming microrobot are established and solved by the method of multiple scales. Experiments on the swimming characteristics of this GMF microrobot in gasoline pipe show that the microrobot can swim at a mean speed of 4.67 mm/s with the external magnetic field driving frequency of 4.7 Hz, which is close to the first primary resonance frequency in gasoline. Besides, the mean swimming speed can reach 2.8 mm/s with the external magnetic field driving frequency of 2.4 Hz, which is close to the superharmonic resonance frequency of order two of GMF cantilever actuator in gasoline.

A common design of piezoelectric microactuators adopts a membrane structure that consists of a base silicon structure, a layer of bottom electrode, a layer of piezoelectric thin film, and a layer of top electrode. In particular, the piezoelectric thin film is often made of lead–zirconate–titanate (PZT) for its high piezoelectric constants. When driven electrically, the PZT thin film extends or contracts flexing the membrane generating an out-of-plane displacement. For PZT thin-film microactuators, residual stresses are unavoidable from fabrication and can significantly reduce the actuation displacement. In this paper, the authors present a fourfold approach to address the issue of residual stresses. First, we demonstrate experimentally that two PZT thin-film actuators may present substantially different displacement and natural frequency even though dimensions of the two actuators are similar. Through a series of finite element analyses, we conclude that only residual stresses can produce such a significant frequency shift reducing the displacement of a PZT thin-film microactuator. Second, we measure the warping of the PZT thin-film actuator via interferometry to detect residual stresses. A simple calculation using shell theories indicates that the warping only causes a tiny shift in natural frequencies. Therefore, most of the degradation of actuator performance results from the nature that residual stresses are in-plane rather than the warping caused by the residual stresses. Third, we develop a vibration analysis to determine when residual stresses could significantly reduce actuator displacement. Fourth, we demonstrate two simple ways to mitigate the negative effects of residual stresses: poling at an elevated temperature and applying a DC bias voltage.

A novel design of a microelectromechanical systems (MEMS) control moment gyroscope (MCMG) was proposed in this paper in order to generate a torque output with a magnitude of 10-6 N∙m. The MCMG consists of two orthogonal angular vibration systems, i.e., the rotor and gimbal, the coupling between which is based on the Coriolis effect and will cause a torque output in the direction perpendicular to the two vibrations. The angular rotor vibration was excited by the in-plane electrostatic rotary comb actuators, while the angular gimbal vibration was driven by an out-of-plane electrostatic parallel plate actuator. A possible process flow to fabricate the structure was proposed and discussed step by step. Furthermore, an array configuration using four MCMGs as an effective element, in which the torque was generated with a phase difference of 90 degrees between every two MCMGs, was proposed to smooth the inherent fluctuation of the torque output for a vibrational MCMG. The parasitic torque was cancelled by two opposite MCMGs with a phase difference of 180 degrees. The designed MCMG was about 1.1 cm × 1.1 cm × 0.04 cm in size and 0.1 g in weight. The simulation results showed that the maximum torque output of a MCMG, the resonant frequency of which was approximately 1,000 Hz, was about 2.5 × 10-8 N∙m. The element with four MCMGs could generate a torque of 5 × 10-8 N∙m. The torque output could reach a magnitude of 10-6 N∙m when the frequency was improved from 1,000 Hz to 10,000 Hz. Using arrays of 4 × 4 effective elements on a 1 kg spacecraft with a standard form factor of 10 cm × 10 cm × 10 cm, a 10 degrees attitude change could be achieved in 26.96s.

In this paper, we describe a novel method of fabricating polymeric 3-D magnetically driven microtools (MMTs) for performing nonintrusive and contamination-free experiments on chips. In order to obtain precise and complicated 3-D patterns from magnetically driven 3-D microtools, a grayscale photolithography technique was applied by making good use of a thick negative photoresist as a sacrifice mold. By controlling the amount of ultraviolet light with a gradation of gray-tone mask, we fabricated a smoothly curved (100-? m gap) object without steps, which tend to appear in the case of conventional layer-by-layer photolithography techniques. A wide range of on-chip applications of microactuators can be realized by using the softness of the polymer-based 3-D MMT. For example, a microfilter and a microloader were successfully operated by a combination of magnetic and fluidic forces. The finite element method analysis of flow showed that a rotation of the 3-D MMT produces a relatively strong downward axial flow, which prevents particles from stagnating on the surface of the MMT. The produced 3-D MMT can be applied to complex on-chip manipulations of sensitive materials such as cells.

International audience; In this paper, we address issues and solutions for micro-electro-mechanical-systems (MEMS) powering through semiconductor devices towards one-chip MEMS, especially those with microactuators that require high voltage (HV, which is more than 10 V, and is often over 100 V) for operation. We experimentally and theoretically demonstrated that the main reason why MEMS actuators need such HV is the tradeoff between resonant frequency and displacement amplitude. Indeed, the product of frequency and displacement is constant regardless of the MEMS design, but proportional to the input energy, which is the square of applied voltage in an electrostatic actuator. A comprehensive study on the principles of HV device technology and associated circuit technologies, especially voltage shifter circuits, was conducted. From the viewpoint of on-chip energy source, series-connected HV photovoltaic cells have been discussed. Isolation and electrical connection methods were identified to be key enabling technologies. Towards future rapid development of such autonomous devices, a technology to convert standard 5 V CMOS devices into HV circuits using SOI substrate and a MEMS postprocess is presented. HV breakdown experiments demonstrated this technology can hold over 700 to 1000 V, depending on the layout. (C) 2018 The Japan Society of Applied Physics.

This paper investigates the effect of dynamic excitation and its utility for enhancement of stable displacement range for a double cantilever-based electrostatic microactuator. A coupled electromechanical problem has been formulated using Galerkin method and solved considering dynamic actuation. The effect of excitation frequency is analyzed thoroughly to estimate the maximum stable displacement range of the actuator. Extensive studies illustrate that for suitable ac voltage–frequency combination, the maximum stable tip deflection for the cantilevers can be obtained even in the range of 50% to 90% of initial gap under specific damping. Such inherent dynamic characteristic of the actuator has been exploited here to achieve larger travel range. Furthermore, the theoretical observation has been experimentally demonstrated with a double microcantilever-based structure fabricated using silicon-on-insulator based process. The experimentation has been carried out using a developed in-house set-up. The major advantage in the present study is that unlike reported literature, the extended range has been achieved here without any additional complex circuits or design modifications. The proposed concept can be extended further to improve the displacement range of other microstructures toward different applications.

We investigate the dynamics and global stability of a beam-based electrostatic microactuator, which is modeled as a first-order approximation of a reduced-order model (ROM) derived using the differential quadrature method (DQM). We show that the ROM dynamics is qualitatively similar to that of a higher-order approximation. We simulate the occurrence of dynamic pull-in for excitations near the first primary resonance using the finite difference method (FDM) and long-time integration. Limit-cycle solutions are obtained using the FDM, the generated frequency- and force-response curves exhibit cyclic-fold, saddle-node, and period-doubling bifurcations. We verify that symmetry breaking is not likely to occur because the orbit is already asymmetric. We identify the basin of attraction of bounded motions using various approximation levels. The simulations reveal that the erosion of the basin of attraction depends heavily on the amplitude and frequency of the AC voltage. We show that smoothness of the boundary of the basin of attraction can be lost and replaced by fractal tongues, which dramatically increase the sensitivity of the microbeam to initial conditions. According to these simulations, the locations of the two fixed points are likely to be disturbed.

Taking advantage of microelectromechanical system technology, a slider with an integrated microactuator (SLIM) for use in hard disc drives was devised. It allows both a lowering to the operating static flying height and a second-stage actuation for ultraprecision track following. By placing the read/write element on a small chiplet rather than on the trailing edge of a slider, the design promises to be cost competitive. This paper provides an overview over the research results achieved so far. It discusses the fabrication technology applied for fabricating both the micromagnetics and micromechanics and presents experimental dynamic test results on SLIM devices which-although not yet flyable-do have fully functional microactuators.

Inhalation therapy is being applied in the home care field to a gradually increasing degree, and therefore two issues of great importance are the convenience and portability of medical devices. Hence, this paper presents a novel cymbal-shaped high power microactuator (CHPM) that includes a ring-type piezoelectric ceramics and a cymbal-shaped micro nozzle plate. The latter can focus energy on the center of the nozzle plate and induce a large force, which provides the cymbal-shaped microactuator with high power to spray medical solutions of high-viscosity produce ultra-fine droplets and increase the atomization rate. In this research, the CHPM can reduce liquids to droplets of an ultra-fine size distribution (Mass Median Aerodynamic Diameter, MMAD), increasing the nebulizing rate and enabling the spraying of high-viscosity fluids (lavender oil, cP>3.5). The ultra-fine droplets were of a MMAD of less than 4.07@mm at 127.89kHz and the atomization rate was 0.5mL/min. The drive voltage of CHPM was only 3V, and the power consumption only one-tenth that of ultrasonic atomizers at 1.2W. The simulation and experiments carried out in this study proved that the droplets are much smaller than those produced by current conventional devices. Therefore, the CHPM is suitable for use in the development of a convenient and portable inhalation therapy device.

Actuators are some of the most important elements in machines and robotics. The need for micro-fabrication of microactuators, smart sensors and microcoils is increasing. Actuators, which have a large volume and weight as part of a product, have been required to reduce their size. However, the processing required for three-dimensional micro-sized structures is very difficult. Here, the LIGA process could be used to fabricate nano- and micro-scale parts for many applications. Therefore, we have fabricated a spiral microcoil with narrow pitch and high aspect ratio coil line structures for an electromagnetic microactuator using the LIGA process. We have fabricated coil lines with a width of 10 μm and an aspect ratio of over 5 on an acrylic pipe surface using the X-ray lithography technique. Then, a void-free copper film was formed by electroforming in order to obtain coil lines. Finally, we have succeeded in obtaining a microcoil with an aspect ratio of over 2 using the isotropic etching process. We have also...

A novel approach of combining nonmagnetic shape memory alloy (SMA) microactuators with electroplated magnetic layers (ML) is presented, which enables the use of two intrinsic actuation principles in a single SMA-ML component allowing considerable gain in functionality. In the present work, we demonstrate local electroplating of Ni-81.75at.%Fe discs onto the surface of Ti-49at.%Ni microbridge structures. Antagonistic SMA-ML microactuators are fabricated by mechanically coupling two SMA-ML microbridges in their center by a spacer and prestraining them with respect to each other. The SMA-ML microactuators show bistable performance in the presence of an inhomogenous magnetic field generated by permanent magnets near the magnetic discs. Compared to antagonistic SMA microactuators fabricated without electroplated discs, a considerable improvement of mechanical performance is achieved. Magnetically enhanced SMA-ML microactuators of 7 × 7 × 4 mm 3 overall size show a blocking force and bistable stroke of about 33 mN and 84 μ m , respectively, while corresponding conventional SMA microactuators show no blocking force and a considerably smaller bistable stroke of 15 μ m .

Simulations of an electromagnetic microsystem intended to be used in a microac- tuator which serves as an ear implant to overcome amblyacousia were conducted. Using the ANSYS TM simulation software, the design and optimization of the electromagnetic microsystem were accomplished by Finite Element Method (FEM) analyses. The design process contained 2-D and 3-D simulations. 2-D simulations served as parametric studies of the system. Afterwards, a 3-D simulation was carried out to flne-tune the results of the 2-D simulation. Comparing the 3-D with the 2-D simulation, the resulting force-air gap data were very close. With respect to the simulations, the designed electromagnetic system fulflls the requirements to drive the microactuator.

There is strong demand for microactuators in medical and industrial fields. For example, minimally invasive surgery has been progressing, and a series of microactuators useful for positioning, grasping and cutting in a narrow space are required. For this purpose, we are investigating micro magnetostrictive actuators using iron–gallium alloy (Galfenol). Galfenol is an iron-based magnetostrictive material with magnetostriction greater than 200 p.p.m., a high relative permeability μ r greater than 100 and a Young's modulus of around 70 GPa. This material is machinable by conventional cutting techniques, and can operate under tensile, bending and impact loads without any degradation in performance. Therefore, a microactuator using Galfenol has advantages over conventional actuators such as electrical motors and piezoelectric actuators in terms of design simplicity, low drive voltage requirements and high robustness. In this paper, we describe two types of actuators consisting of a U-shape core of Galfenol — o...

We discuss the use of a flat-plane slider for a surface acoustic wave (SAW) motor. For stable driving, the SAW motor requires a silicon slider with many microprojections on its surface. Previously,...

In this paper, the effect of material and dimensional uncertainties on performance of electrothermal microactuator is investigated. A simple and efficient uncertainty analysis method is used based on direct linearization method; also uncertainty analysis is performed by creating second-order metamodel through Box-Behnken design and Monte Carlo simulation. The results demonstrate how these uncertainties affect the microactuator tip deflection by confidence limit bands. The standard deviations of tip deflection obtained by these two probabilistic methods are very close.

This paper explores a comparative study between different designs of electrothermal microactuators with emphasis on optimal design and performance key factors. For this purpose, two typical designs for electrothermal microactuators with the same material properties are studied: one with different beam lengths (design A), other one with different beam sections and a flexure part (design B). Analytical model and finite element model (FEM) have been developed and validated by comparison of simulation results with experimental results in literature. Optimal geometrical dimensions to achieve maximum deflection have been obtained using genetic algorithm (GA). As the key factors, temperature distribution, power consumption and deflection of these microactuators have been compared in the range of microactuator functionality. Design B is more sensitive to geometrical dimension variation. Using optimal geometrical dimensions, an increase of almost 40 and 55% has been achieved for design A and B tip deflections, respectively. The modified design A with a gold layer results to an increase of 70% for tip deflection comparing to its optimal design.

On purpose to realize flexible electro-rheological microactuators (FERMA), this paper presents a MEMS-based flexible ER microvalve (FERV) by integrating thin SU-8 cantilever structures and the SU-8-sandwiched microfluidic channels for homogeneous ER fluids. The structure of the FERV is the fluidic channel-embedded cantilever. The FERV is successfully fabricated with 5 mm in length, 2.4 mm in width and 0.2 mm in thickness and the bending of the FERV shows enough flexibility. The static and dynamic characteristics of the FERV are experimentally investigated. The controllable pressure change rate of the FERV is about 70% of the supply pressure and the step-up response time is about 0.25 s. There is not such a difference of the static and dynamic performance between a straight FERV and a bent FERV, showing that bending does not affect the characteristics of the FERV. A bellows-type FERMA is realized and its elongation is 4.8 mm. The experimental results prove the feasibility of FERMA.

Magnetic Shape Memory (MSM) alloys are a new class of “smart” materials. In the martensite state, they exhibit a reversible strain due to a reorientation of twin variants, based on twin boundary motion driven by an external magnetic field occurring in the martensite state. This effect allows for the development of linear microactuators. This work presents the simulation results for the fabrication of a microactuator based on an MSM alloy with an optimized design. A stator element consists of a NiFe45/55 flux guide, two poles, and double-layer Cu coils wound around each pole for generating the magnetic field. The MSM material applied is NiMnGa. The integrated microactuator is subjected to dynamic simulation, using a “checkerboard” pattern to locally switch the magnetic properties when the relative permeability µr is changed. The model is described with the Ansys Parametric Design Language (APDL). Design, modeling, and simulation of the magnetic system including MSM material, are conducted by Finite Element Method (FEM) analysis using the software tool ANSYS™.

Feedback control of microelectromechanical systems (MEMS) devices has the potential to significantly improve device performance and reliability. One of the main obstacles to its broader use is the small number of on-chip sensing options that are available to MEMS designers. A method of using integrated piezoresistive sensing is proposed and demonstrated as another option. Integrated piezoresistive sensing utilizes the inherent piezoresistive property of polycrystalline silicon from which many MEMS devices are fabricated. As compliant MEMS structures flex to perform their functions, their resistance changes. That resistance change can be used to transduce the structures' deflection into an electrical signal. The piezoresistive microdisplacement transducer (PMT) is a demonstration structure that uses integrated piezoresistive sensing to monitor the output displacement of a thermomechanical inplane microactuator (TIM). Using the PMT as a feedback sensor for closed-loop control of the TIM provided excellent tracking with no evident steady-state error, maintained the positioning resolution to plusmn29 nm or less, and increased the robustness of the system such that it was insensitive to significant damage.

The giant magneto-strain effect is particularly attractive for actuator applications in micro- and nanometer dimensions as it enables contact-less control of large deformations, which can hardly be achieved by other actuation principles in small space. Two different approaches are being pursued to develop ferromagnetic shape memory (FSMA) microactuators based on the magnetically induced reorientation of martensite variants: (1) the fabrication of free-standing epitaxial Ni-Mn-Ga thin film actuators in a bottom-up manner by magnetron sputtering, substrate release and integration technologies and (2) the top-down approach of thickness reduction of bulk Ni-Mn-Ga single crystals to foil specimens of decreasing thicknesses (200 – 40 μm) and subsequent integration. This review describes the fabrication technologies, procedures for thermo-mechanical training adapted to the quasi-two-dimensional geometries of film and foil specimens as well as the performance characteristics of state-of-the art actuators after processing and training.

This paper reports the design, fabrication, modeling, and analysis of an electrochemical microactuator (ECM). The driving mechanism of the ECM is based on the reversible electrolysis process of water. The expansion and shrinkage of gas bubbles generated in a micro electrochemical chamber during a reversible electrolysis process can be used for actuation in microfluidic systems. The fluidic components of the ECM were fabricated on a glass substrate using UV lithography of SU-8. Two electrodes were used, with one Pt black (coated with platinum nanoparticles) as working and auxiliary electrode and the other Ag/AgCl coated as reference. The nano particles coated on the working electrode help to boost the surface-to-volume ratio of the electrode and to obtain higher operation frequency. Pulse electropotentials were supplied for active control of expansion and shrinkage of gas bubbles using reproducible electrochemical reactions. The theoretical volume change rate of gas bubbles was simulated as a function of time using the ideal gas law and compared with the measured volume change. The experimental results show the electrode coated with platinum nanoparticles helped to enhance the reversible electrolysis process significantly. The results also show that the dynamic model can be used to simulate the dynamic behaviors of the ECM actuator. The ECM can be used in microfluidic applications such as pumping or valves.

Important advancements have been recently achieved in the field of neural interfaces to restore lost sensory and motor functions. The aim of this letter was to develop an innovative approach to increase the selectivity and the lifetime of polyimide-based intrafascicular electrodes. The main idea was to obtain a neural interface that is able to restore a good signal quality by improving the electrical connection between the active sites and the surrounding axons. The high flexibility of polyimide-based neural interfaces allows to embed microactuators in the interface core and achieve desired microdisplacements of the active sites. Nearly equiatomic nickel-titanium alloy was selected as a microactuator because of its shape memory effect. A single TiNi thin film was obtained by dc magnetron sputtering, and was segmented into four distinct sectors. This solution allowed the independent actuation of the different active sites (multiactuation). A corrugated profile was impressed to the new actuated intraneural (ACTIN) interface. The active sites were positioned in correspondence to the peaks of the corrugation, thus maximizing the effects of the single actuations. The technological results, the electrical properties, the thermal behavior, and eventually, the actuation performances of the current ACTIN prototype are shown and discussed. The actuation cycle was thermally compatible for biomedical applications. Promising results were obtained from the current ACTIN prototype with an average controlled movement of 7 microm of the peaks.

Time-dependent deformation (creep) behaviors of piezoelectric microactuators have been investigated. Position (or gap height) drift of microbridged actuator beam and its displacement amplitude change with time could be attributed to the anelastic behavior of the driving unit itself based on lead zirconate titanate (PZT) in the actuator, and as well as to the mechanical stress states established in the microactuator beam after the surface release of the micromachined actuator structure. From creep analyses of a simple microcantilever and microbridge beam structures, it was turned out that the overall creep behavior in microbridged piezoactuator structure was mainly dependent on the actuator beam initial deflection configuration governed both by residual stress of the actuating part Pt/PZT/Pt stack and the stress gradient through the silicon nitride (SiNx) microbridge beam.

Magnetic force-enhanced gene delivery provides a promising method for an efficient transfection even to single cells. Conjugating genes with magnetic nanoparticles allows for the magnetic manipulation of these complexes. This paper presents the concept, modeling, and fabrication technology for a magnetic microactuator designed as a pole row for magnetically actuating these complexes. For conducting preliminary tests, a scaled-up model of the micro pole row was created.

The paper describes the tests performed to determine the characteristics of four various leaf springs, as well as the evaluation of the mounting platform/chiplet motion as a function of the excitation current. For the leaf spring evaluation, a nanoindenter (Hysitron Tribo Indenter) was used. To determine the variation of the air gap as a function of the excitation current, optical microscopy as well as laser Doppler vibrometry (LDV) was applied.

The next generation of tissue engineered constructs (TECs) requires the incorporation of a controllable and optimized microstructure if they are to chemically, mechanically, and biologically mimic tissue function. In order to obtain TECs with optimized microstructures, a combination of spatiotemporally regulated mechanical and biochemical stimuli is necessary during the formation of the construct. While numerous efforts have been made to create functional tissue constructs, there are few techniques available to stimulate TECs in a localized manner. We herein describe the design of a microdevice which can stimulate TECs in a localized, inhomogeneous, and predefined anisotropic fashion using ferromagnetically doped polydimethylsiloxane microflaps (MFs). Specifically, a sequential magneto-structural finite element model of the proposed microdevice is constructed and utilized to understand how changes in magnetic and geometrical properties of the device affect MF deflection. Our study indicates that a relatively small density of ferromagnetic material is required to result in adequate force and MF defection (175 microm approximately 7% TEC strain). We also demonstrate that MF to magnet distance is more important than inherent MF magnetic permeability in determining resulting MF deflection. An experimental validation test setup was used to validate the computational solutions. The comparison shows reasonable agreement indicating a 5.9% difference between experimentally measured and computationally predicted MF displacement. Correspondingly, an apparatus with two MFs and two magnets has been made and is currently undergoing construct testing. The current study presents the design of a novel magnetic microactuator for tissue engineering applications. The computational results reported here will form the foundation in the design and optimization of a functional microdevice with multiple MFs and magnets capable of stimulating TECs in nonhomogenous and preferred directions with relevant spatial resolution.

In this work, a color-oscillating system is first developed by combining the intrinsic peristaltic motion of a Landolt pH-oscillator with the structure color of a well-designed pH-sensitive photonic crystal hydrogel. As a result, the pH oscillation reaction procedure could be distinctly monitored by the distinct change of structure color/optic signal. The oscillation rhythm of the pH well coincides with that of the stopband/structure color. The oscillation detail of each cycle can also be clearly monitored by color change. This work would be of great significance for the promising applications of real-time monitoring of the microactuator by optical signal or structure color.

In this study we used the commercial 0.35 µm CMOS (complementary metal oxide semiconductor) process and simple maskless post-processing to fabricate an array of micromirrors exhibiting high natural frequency. The micromirrors were manufactured from aluminum; the sacrificial layer was silicon dioxide. Because we fabricated the micromirror arrays using the standard CMOS process, they have the potential to be integrated with circuitry on a chip. For post-processing we used an etchant to remove the sacrificial layer and thereby suspend the micromirrors. The micromirror array contained a circular membrane and four fixed beams set symmetrically around and below the circular mirror; these four fan-shaped electrodes controlled the tilting of the micromirror. A MEMS (microelectromechanical system) motion analysis system and a confocal 3D-surface topography were used to characterize the properties and configuration of the micromirror array. Each micromirror could be rotated in four independent directions. Experimentally, we found that the micromirror had a tilting angle of about 2.55° when applying a driving voltage of 40 V. The natural frequency of the micromirrors was 59.1 kHz.

We propose a miniature spherical motor using iron–gallium alloy (Galfenol). This motor consists of four rods of Galfenol with square cross-section, a wound coil, a permanent magnet, an iron yoke and a spherical rotor placed on the edge of the rods. The magnetomotive force of the magnet provides bias magnetostriction for the rods and an attractive force that maintains the rotor on the rods. When currents of 180° phase difference flow in pairs of opposing coils, a torque is exerted on the rotor by pushing (expansion) and pulling (contraction) of the rods. Rotation about a single axis is realized by a sawtooth current, such that the rotor rotates with slow expansion and slips at the rapid contraction. The motor can be fabricated at small sizes and driven with a low voltage, suitable for application as a microactuator for rotating the camera and mirror in endoscopes.

This paper reports on the first investigation to design, build and characterize a dual vertical and horizontal microactuator based on the topology of a thermal chevron actuator. The chevron-based vertical actuator displays superior performance in comparison to existing electrostatic and electrothermal vertical actuators. The device has the capacity to produce linear vertical motion without deformation of the upper beam surface and is well suited for a variety of optical and microassembling applications. A methodology that may extend the capabilities of standard surface micromachining MEMS technology to design three-dimensional structures is also presented.

Microactuators provide controlled motion and force for applications ranging from radio frequency switches to microfluidic valves. Large amplitude response in piezoelectric actuators requires amplification of the small strain, exhibited by the piezoelectric material, used in the construction of such actuators. This paper studies a uniflex microactuator that combines the strain amplification mechanisms of a unimorph and flexural motion to produce large displacement and blocking force. The design and fabrication of the proposed uniflex microactuator are described in detail. An analytical model is developed with three connected beams and a reflective symmetric boundary condition that predicts actuator displacement and blocking force as a function of the applied voltage. The model shows that the uniflex design requires appropriate parameter ranges, particularly the clearance between the unimorph and aluminum cap, to ensure that both the unimorph and flexural amplification effects are realized. With a weakened joint at the unimorph/cap interface, the model is found to predict the displacement and blocking force for the actuators fabricated in this work.

Sensors and actuators based on magnetic, electromagnetic, and electrodynamic principles allow the realization of a wide range of Magnetic Micro Electro-magnetic Systems (magnetic MEMS). Preconditions for fabricating such devices is the availability of enabling technologies like deposition technologies for magnetic materials or high aspect ratio micro structure technologies (HARMST) for creating coils and core structures. Examples for microsensor applications are the use of either magnetoelastic effects for strain gauge measurements and the inductive effect for measuring the properties of thin-films during the wafer fabrication of magnetic MEMS devices. Magnetic microactuation applications are for instance microactuator with latching capabilities, a rather simple micro synchronous motors, and a hard disc drive (HDD) recording head featuring a Slider with an Integrated Microactuator (SLIM) for second stage actuation.

We succeeded in reducing magnetic interaction region with a focused magnetic field on-chip. Novelty of this paper is summarized as follows. (1) We used neodymium powder as the main component of magnetically driven microtools (MMT). The density of magnetic flux was improved by about 100 times after magnetization. (2) We fabricated a couple of pin mounted under a microfluidic chip. The density of magnetic flux was improved by about 1.8 times. As a result, the density of magnetic flux had a single peak using the pin, unlike in a setup without pins. It was confirmed that the size of the magnetic interaction region for the current setting was one twentieth that of the previous setting.

Micromanipulation is a hot topic in the rapidly emerging area of micromechatronics and particularly in the manufacturing and assembling of micromechatronic products. This paper introduces an integrated mechatronic approach for the systematic design and operation of flexible, sensorless, automated micromanipulation for a variety of microparts on microactuation arrays. This approach is a mechatronic synthesis of methods from different engineering areas such as solid modeling, electronics design, software for control and programming of mechanical actuation. It involves designing of programmable force fields for manipulation of convex or non-convex polygonal microparts on an array, hardware programmable circuitry for the activation of the array and a software algorithmic procedure for the programming. A detailed analysis is given, as well as several simulated experiments performed using the introduced approach on a cilia microactuator array for a variety of polygonal asymmetric and non-convex microparts and the results are presented and discussed. Finally, the advantages and limitations of this approach are analyzed and points for further research are raised.

Electrostatic comb-drive microactuators were fabricated by electron beam lithography on a 260-nm-thick silicon layer of a silicon-on-insulator wafer. The actuators consisted of comb electrodes, springs, and a frame. Two kinds of microactuators with doubly clamped and double-folded springs were designed and fabricated. The comb electrode was as small as 2.5 mum wide and 8 mum long and was composed of 250-nm-wide, 260-nm-thick, and 2-mum-long fingers. The air gap between the fingers was 350 nm. The spring was 250 nm wide, 260 nm thick, and 17.5 mum long, and the spring constant was 0.11 N/m. The force and displacement generated by the microactuator were 2.3 x 10-7N and 1.0 mum, respectively. Applying an ac voltage, the oscillation amplitude became maximum at a frequency of 132 kHz. The mechanical and electrical characteristics of the fabricated actuators were investigated quantitatively.

The present study is aimed to develop an optimization approach which is employed to design an electro-thermal microactuator based on numerical simulation of the device performance. The microactuator basically adopts a bimorph structure which consists of a P-type silicon layer and an aluminum layer. A finite-element multi-physics code (ANSYS 10.0) is used to develop the direct problem solver for predicting the stress/stain, electric, and thermal fields associated with the varying material layers thicknesses during the iterative optimization process. The simplified conjugate-gradient method (SCGM) is used as the optimization method. Regarded as a test case, the modifications of a conventional design, which suffered from high temperature, excessive power consumption, and oxidization of aluminum layer, are attempted. In this study, firstly the direct problem solver is used to predict the performance of various design models so as to select the best one with highest performance. Parametric study of the best design model is then performed, and based on the solutions yielded from the parametric study, the subtle influence of thicknesses of the P-type silicon and the aluminum layers ( t S and t AL ) on the performance of the microactuator is observed. Finally, the developed optimization approach is applied to predict the optimal combination of the geometrical parameters. The optimal thicknesses of the material layers used in the microactuator are successfully determined, and the optimization process leads to a great improvement in the performance of the microactuator. Results also show that the approach is robust and the obtained optimal combination of the geometrical parameters is independent of the initial guess for the particular case.

This paper is focused on the design and fabrication of a four-arm-structure microelectromechanical systems gripper integrated with sidewall piezoresistive force sensors. Surface and bulk micromachining technologies are employed to fabricate the microgripper from a single-crystal silicon wafer (i.e., no silicon-on-insulator wafer is used). A vertical sidewall surface piezoresistor etching technique is used to form the side direction force sensors. The end effector of this gripper is a four-arm structure: two fixed cantilever arms integrated with piezoresistive sensors are designed to sense the gripping force. The resolution of the force sensor is in the micronewton range and, therefore, provides feedback of the forces that dominate the micromanipulation processes. An electrostatically driven microactuator is designed to provide the force to operate the other two movable arms. In this way, it creates a deflection of 25 mum at the arm tip, and the range of the operation is 30-130 mum. Experimental results show that it can successfully provide force sensing and play a main role in preventing the damage of microparts in micromanipulation and microassembly tasks.

A pneumatically operated four-fingered micromanipulator (a ldquomicrohandrdquo) with a fiber-based internal visual system is developed using microelectromechanical systems fabrication techniques. This ldquoseeingrdquo microhand transfers images generated by the optical system equipped at the palm of the microhand to an operator via an optical fiber bundle to provide the shape and distal information of objects of interest. The use of illuminating fibers along with the optical bundle enables the microhand's operation even in light-deficient environments. Such visual information informs the accurate relative location of the device and the status of manipulation to the operator in real time, who will take subsequent actions accordingly with an increased accuracy and efficiency. Embedding the fiber-based optical system inside the manipulator, instead of using an external camera setup for overall system monitoring, greatly reduces the size of the manipulator and helps increase maneuverability, particularly when operating in a space-limited work area. Tests have been conducted to verify the performance of the visually aided microhand to manipulate millimeter-sized objects in real time. Building on the ability of the UCLA microhand to gently handle irregular-shaped objects, this vision-enabled microhand is expected to provide more accurate manipulations and widen the window of applications.